BIOL220 Physiological Adaptions of Plants

Branch (definition)

(1) A part of a phylogenetic tree that represents populations through time. (2) A lateral extension of a plant's shoot system.

Node (definition)

(1) In animals, any small thickening (e.g., a lymph node). (2) In plants, the part of a stem where leaves or leaf buds are attached. (3) In a phylogenetic tree, the point where two branches diverge, represent- ing the point in time when an ancestral group split into two or more descendant groups. Also called fork.

What are the three tissue systems found in plants?

(1) The dermal tissue system. (2) The ground tissue system. (3) The vascular tissue system.

Herbivore (definition)

(adjective: herbivorous) An animal that eats primarily plants and rarely or never eats meat.

Pathogen (definition)

(adjective: pathogenic) Any entity capable of causing disease, such as a microbe, virus, or prion.

Ground Tissue System: Mesophyll Cells (definition, types, function)

*Definition* A type of cell, found near the surfaces of plant leaves, that is specialized for the light-capturing reactions of photosynthesis. *Types:* Spongy, Pallisade *Function:*

Pith (definition, other)

*Definition* In the shoot systems of plants, ground tissue located to the inside of the vascular bundles. Roots of some plants also have a pith. Other: The ground tissue that the vascular tissue runs through is divided into two major regions: pith, the ground tissue that is toward the center of the stem, and cortex, the ground tissue that is between the vascular bundles and the epidermis. The roots of some plants also have distinct pith and cortex regions.

Meristem (definition, mechanism)

*Definition:* (adjective: meristematic) In plants, a group of undifferentiated cells, including stem cells, that can divide and develop into various adult tissues throughout the life of a plant. *MEchanism:* When meristematic cells divide, some of the daughter cells remain in the meristem, allowing the meristem to persist. Other cells, though, differentiate into distinct cell types with specific functions.

Cambium (definition, other)

*Definition:* (plural: cambia) In woody plants, tissue that consists of two types of cylindrical meristems that increase the width of roots and shoots through the process of secondary growth. *Other:* It is a special type of meristem (also called a lateral meristem) that differs from an apical meristem in two ways: 1. A cambium forms a cylinder that runs the length of a root, tree trunk, or branch and is made up of a single layer of meristematic cells. In contrast, apical meristems are clusters of cells localized at root tips and shoot tips. 2. In a cambium, and only there, cells divide in a way that increases the width of roots, trunks, and branches. Cells in an apical meristem, in contrast, divide in a way that extends the length of roots and shoots.

Dermal Tissue System: Stomata (definition, role)

*Definition:* (singular: Stoma) Generally, a pore or opening. In plants, a microscopic pore on the surface of a leaf or stem through which gas exchange occurs; typically surrounded by specialized cells that open the pore. *Role:* Found on leaves, which are pores that allow CO2 to enter and O2 to exit photosynthetically active tissues. A stoma is surrounded by two specialized guard cells, which change shape to open or close the stoma. When stomata are open, CO2, O2, water vapor, and other gases can move between the atmosphere and the interior of the plant by diffusion. *Mechanism:* - *Stomata Open:* Stomata open when adequate water is available and CO2 is needed for photosynthesis. When stomata are open, water diffuses from the moist interior of the leaf to the surrounding atmosphere. - *Stomata Closed:* Stomata close when conditions are dry. This prevents large amounts of water from being lost by transpiration.

Chloroplast (definition, other)

*Definition:* A chlorophyll-containing organelle, bounded by a double membrane, in which photosynthesis occurs; found in plants and algae. Also the location of starch, amino acid, fatty acid, purine, and pyrimidine synthesis. *Other:* Leafs are the site of photosynthesis. Non-photosynthetic cells found in roots, seeds, flower petals, and other locations may have organelles that are similar to chloroplasts but are specialized for storing pigments, starch, oils, or proteins.

Apical Meristem (definition, location, mechanism)

*Definition:* A group of undifferentiated plant cells, at the tip of a shoot or root, that is responsible for primary growth. *Location:* Are located at the tip of each root and shoot. *Mechanism:* As cells in apical meristems divide, enlarge, and differentiate, root and shoot tips extend the plant body outward, allowing it to explore new space.

Dermal Tissue System: Trichomes (definition, structure, role)

*Definition:* A hairlike appendage that grows from epidermal cells in the shoot system of some plants. Trichomes exhibit a variety of shapes, sizes, and func- tions depending on species. *Structure:* They are hairlike appendages made up of specialized epidermal cells. They are found in shoot systems and come in a wide variety of shapes, sizes, and abundances. *Role:* Protect the individual from the damaging effects of intense sunlight and attacks by herbivores. Depending on the species, trichomes may: (1) Keep the leaf surface cool by reflecting sunlight. (2) Reduce water loss by forming a dense mat that limits transpiration. (3) Provide barbs or store toxic compounds that thwart herbivores. (4) Trap and digest insects.

Vacuole (definition, other)

*Definition:* A large organelle in plant and fungal cells that ordinarily is used for bulk storage of water, pigments, oils, or other substances. Some vacuoles contain enzymes and have a digestive function similar to lysosomes in animal cells. *Other:* Vacuoles contain an aqueous solution called cell sap, store wastes and in some cases also digest wastes, as do animal lysosomes. In addition, plant vacuoles store water and nutrients. They may also hold pigments that provide color, or poisons that deter herbivores.

Simple Leaf (definition, other)

*Definition:* A leaf consisting of a single blade defined by the presence of a single axillary bud where the petiole joins the branch or stem. *Other:* The defining feature of an individual leaf (whether simple or compound) is the presence of an axillary bud where the petiole joins the stem.

Compound Leaf (definition, other)

*Definition:* A leaf consisting of two or more blades but defined by the presence of a single axillary bud where the petiole joins the branch or stem. *Other:* Although a compound leaf easily can be mistaken for several individual leaves, the defining feature of an individual leaf (whether simple or compound) is the presence of an axillary bud where the petiole joins the stem.

Root Hair (definition, other)

*Definition:* A long, thin outgrowth of the epidermal cells of plant roots, providing increased surface area for absorption of water and nutrients. *Other:* - Root hairs furnish the actual sites of water and nutrient absorption. - The rest of the root system provides structural support for the root hairs, conducts water and nutrients to the shoot, stores the products of photosynthesis, and anchors the plant in the soil. Uptake of water and nutrients by root hairs is vital to plants.

Tuber (definition, other, example)

*Definition:* A modified plant rhizome that functions in storage of carbohydrates. *Other:* Tubers are underground, swollen rhizomes that function as carbohydrate-storage organs. *Ex:* The eyes of a potato—a typical tuber—are nodes in the stem where new branches may arise.

Thorn (definition, other)

*Definition:* A modified plant stem shaped as a sharp, protective structure. Helps protect a plant against feeding by herbivores. *Other:* Thorns are modified stems that help protect the plant from attacks by large herbivores, or plant eaters, such as deer, giraffe, or cattle.

Stolon (definition, other)

*Definition:* A modified stem that runs horizontally over the soil surface and produces new plants at the nodes (a form of asexual reproduction). *Other:* They are modified stems that grow horizontally along the soil surface, producing adventitious roots and leaves at each node. Because new plants form at these nodes, stolons function in asexual reproduction. Stolons grow aboveground.

Rhizome (definition, other, example)

*Definition:* A modified stem that runs horizontally underground and produces new plants at the nodes (a form of asexual reproduction). *Other:* Like stolons, rhizomes are stems that grow horizontally instead of vertically. They produce new plants at nodes and thus participate in asexual reproduction. But while stolons grow aboveground, rhizomes spread belowground. *Ex:* One quak-ing aspen plant in Utah was found to have 47,000 stems rising from a network of rhizomes, making it one of the largest organisms known. What we see as individual aspen trees are actually stems that are connected underground.

Phloem (definition, function, cell types)

*Definition:* A plant vascular tissue that conducts sugars between roots and shoots; contains sieve-tube elements and companion cells. Primary phloem develops from the procambium of apical meristems; secondary phloem, from the vascular cambium. *function:* Transport of sugars, amino acids, hormones, etc.; support. The phloem of many plants also includes fibers that aid in structural support. *Cell Types:* two specialized types of cells: sieve-tube elements and companion cells

Xylem (definition, structure, function, cell types)

*Definition:* A plant vascular tissue that conducts water and ions; contains tracheids and/or vessel elements. Primary xylem develops from the procambium of apical meristems; secondary xylem, or wood, from the vascular cambium. *Structure:* The xylem of many plants includes water- conducting cells as well as parenchyma cells and fibers. *Function:* Transport of water and nutrients; structural support. Conducts water and dissolved nutrients in one direction: from the root system to the shoot system. *Cell Types:* The two types of water-conducting cells in xylem are tracheids and vessel elements. The xylem of all vascular plants contains tracheids. In angiosperms, as well as members of the Gnetophyta and a few other groups of vascular plants, xylem also contains vessel elements.

Dermal Tissue System: Cuticle (definition, structure, role, trade offs)

*Definition:* A protective coating secreted by the outermost layer of cells of an animal or a plant; often functions to reduce evaporative water loss. *Structure:* Most shoot epidermal cells are flattened and usually lack chloroplasts. Epidermal cells in the shoot system fulfill their protective role in part by secreting the cuticle—a waxy layer that forms a continuous sheet on the surface of leaves and stems *Role:* - The cuticle reduces the amount of water that stems and leaves lose by evaporation. - The cuticle forms a barrier to protect the plant from viruses, bacteria, and the spores or growing hyphae of parasitic fungi. The plant epidermis forms the first line of defense against disease-causing agents, or pathogens. *Trade-Offs:* Waxes found in the cuticle can also be detrimental to the plant, however, by reducing gas exchange. This is a problem because photosynthesis depends on the free flow of carbon dioxide to photosynthetic cells.

Root Cap (definition, function, other, cell populations)

*Definition:* A small group of cells that covers and protects the root apical meristem. Senses gravity and determines the direction of root growth. *Function:* Protects the root apical meristem. The root cap cells are also important in sensing gravity and determining the direction of growth. They also synthesize and secrete a slimy, polysaccharide-rich substance that helps lubricate the root tip, reducing friction and protecting the apical meristem as it is pushed through soil. *Other:* Cells produced by the meristem constantly replenish the cap, which regularly loses cells. *Three populations of cells exist behind the root cap:* 1. Zone of Cellular Division 2. Zone of Cellular Elongation 3. Zone of Cellular Maturation.

Needlelike Leaves (loose definition, other)

*Definition:* A small, narrow leaf with small surface area. *Other:* - Plants that thrive in deserts and in cold, dry habitats tend to have needlelike leaves. - The leading hypothesis to explain this pattern is based on two observations: (1) Water is often in short supply in these environments because it is scarce in deserts, or frozen and thus unavailable in cold habitats. (2) Leaves with large surface areas lose large amounts of water through an evaporative process called transpiration. Needlelike leaves are interpreted as adaptations that minimize transpiration in water-scarce habitats. Small, narrow leaves are also much less susceptible to wind damage than are large, broad leaves.

Primary Plant Body (definition)

*Definition:* All of the cells and tissues derived from apical meristems and primary meristems. *Other:* All of the cells and tissues that are derived directly from apical meristems constitute the primary plant body.

Plant Body (definition, other)

*Definition:* An entire plant, generally consisting of the root and shoot systems. *Other:* - Absorption takes place across a surface. The cells that use the absorbed molecules and light occupy volume. A plant body is more efficient as an absorption and synthesis machine when it has a large surface area relative to its volume.

Ground Tissue System: Sclerenchyma (definition, structure, cell types)

*Definition:* Can refer to tissue or cell type. In plants, a cell that has a thick secondary cell wall and provides support; typically contains the tough structural polymer lignin and usually is dead at maturity. Includes fibers and sclereids. *Structure:* characterized by the presence of the thick, rigid secondary cell wall in addition to the relatively thin primary cell wall. Unlike the primary cell wall, the secondary cell wall contains the tough, rigid compound lignin in addition to cellulose. sclerenchyma cells are usually dead at maturity—meaning they contain no cytoplasm. *Function:* The nonexpandable secondary cell wall of sclerenchyma cells specializes them for supporting stems and other structures after growth has ceased. *Cell Types:* Two types of sclerenchyma cells are recognized: fibers and sclereids.

Ground Tissue System: Parenchyma (definition, structure, function

*Definition:* Can refer to tissue or cell type. In plants, a general type of cell with a relatively thin primary cell wall. These cells, found in leaves, the centers of stems and roots, and fruits, are involved in photosynthesis, storage, and transport. *Structure:* Composed of parenchyma cells, which have relatively thin primary cell walls and are the most common and versatile ground tissue cells. Parenchyma represents a simple tissue. *Function:* Synthesis and storage of sugars and other compounds - The parenchyma tissue in leaves consists of parenchyma cells filled with chloroplasts, and it is the primary site of photosynthesis. - In other organs, parenchyma cells store starch granules. Ex: When you eat a potato or an apple, you are ingesting primarily parenchyma cells. - Many parenchyma cells are totipotent, meaning they retain the capacity to divide and develop into a complete, mature plant. The totipotency of parenchyma cells is important in healing wounds and in reproducing asexually via stolons or rhizomes. In each case, parenchyma cells may begin to divide, grow, and differentiate to form new roots and shoots. The totipotency of parenchyma cells also allows gardeners to clone plants by making cuttings. - Ex: If you cut a piece of stem from a coleus plant and place it in water, parenchyma cells will divide to produce a mass of undifferentiated cells called a callus. Roots then develop from the callus, and the new individual can be planted in soil.

Ground Tissue System: Collenchyma (definition, structure, function, example)

*Definition:* Can refer to tissue or cell type. In plants, an elongated cell with cell walls thickened at the corners that provides support to growing plant parts; usually found in strands along leaf veins and stalks. *Structure:* Similar to parenchyma cells but are characterized by an unevenly thickened primary cell wall and are longer and thinner than parenchyma cells. Collenchyma represents another example of a simple tissue. Collenchyma tissue is often found just under the epidermis of stems, especially outside vascular bundles. *Function:* Support (mostly in stems and leaves). Collenchyma cells are not rigid, and their ability to stretch allows stems to flex in the wind without tearing or breaking. These cells provide flexible structural support for shoots. Ex: The "strings" you may have peeled from a stalk of celery or rhubarb include many strands of collenchyma cells

Vascular Bundle (definition, other)

*Definition:* In a plant stem, a cluster of xylem and phloem strands that run the length of the stem. *Other:* - Just behind each shoot apical meristem, the primary meristems give rise to dermal, ground, and vascular tissues. - Vascular tissues are grouped into vascular bundles, which form strands running the length of the stem. - The ground tissue that the vascular tissue runs through is divided into two major regions: pith, the ground tissue that is toward the center of the stem, and cortex, the ground tissue that is between the vascular bundles and the epidermis. The roots of some plants also have distinct pith and cortex regions. - *Eudicots:* In sunflowers and other eudicots, the vascular bundles are arranged in a ring near the stem's perimeter. The arrangement of vascular tissue in eudicots is significant and is associated with the ability to produce secondary growth. - *Monocots:* The arrangement of the vascular bundles and ground tissue is dramatically different in the stems of monocots such as grasses, lilies, and orchids. vascular bundles in monocot stems are normally scattered throughout the ground tissue.

Zone of Cellular Division (definition, structure)

*Definition:* In plant roots, a group of apical meristematic cells just behind the root cap where cells are actively dividing. *Structure:* Contains the apical meristem, where cells actively divide, along with the protoderm, ground meristem, and procambium, where additional cell division occurs.

Zone of Cellular Maturation (definition, other)

*Definition:* In plant roots, a group of plant cells, located several millimeters behind the root cap, that are differentiating into mature tissues. Site of most nutrient uptake. *Other:* - The zone of cellular maturation is the most important root segment in terms of water and nutrient absorption. - In this region, epidermal cells produce outgrowths called root hairs, which greatly increase the surface area of the dermal tissue. - The zone of cellular maturation is also where lateral roots begin to grow. In contrast to lateral branches in the shoot, which arise from meristems in axillary buds, lateral roots arise within a ring of cells around the vascular tissue and then erupt through the surrounding ground tissue.

Zone of Cellular Elongation (definition, other)

*Definition:* In plant roots, a group of young cells, derived from primary meristem tissues and located behind the apical meristem, that are increasing in length. *Other:* - The zone of cellular elongation is the region most responsible for the growth of roots through the soil. - The cells in this region increase in length by taking up water. Their expansion provides the force that pushes the root cap and apical meristem through the soil. - When environmental conditions are good, roots can extend by as much as 4 centimeters per day.

Companion Cell (definition, other, function)

*Definition:* In plants, a cell in the phloem that is connected via many plasmodesmata to adjacent sieve- tube elements. Companion cells provide materials to maintain sieve-tube elements and function in the loading and unloading of sugars into sieve-tube elements. *Structure:* Contain most of the organelles normally found in plant cells and support the metabolic activity of sieve-tube elements. They are alive at maturity and lack secondary cell walls. *Function:* Are not conducting cells, but instead provide materials to maintain the cytoplasm and plasma membrane of sieve-tube elements.

Cortex (definition, other)

*Definition:* In plants, a layer of ground tissue found outside the vascular bundles of roots and outside the pith of a stem. *Other:* The ground tissue that the vascular tissue runs through is divided into two major regions: pith, the ground tissue that is toward the center of the stem, and cortex, the ground tissue that is between the vascular bundles and the epidermis. The roots of some plants also have distinct pith and cortex regions.

Sclerenchyma Cells: Sclereids (definition, structure, function, other)

*Definition:* In plants, a relatively short type of sclerenchyma cell that usually functions in protection, such as in seed coats and nutshells. *Structure:* Relatively short, have variable shapes, and often function in protection. *Function:* Protection (mostly in hard outer surfaces of seeds and fruits). *Other:* The tough coats of seeds and the thick shells of nuts are composed of sclereids; these cells are also responsible for the gritty texture of pears.

Sclerenchyma Cells: Fiber (definition, structure, function, other)

*Definition:* In plants, a type of elongated sclerenchyma cell that provides support to vascular tissue. *Structure:* Extremely elongated cells. Fiber cells can be over half a meter long in some cases. *Function:* Support (mostly in stems and leaves) *Other:* Fiber cells are important in the manufacture of paper, hemp or jute ropes, and linen and other fabrics.

Sieve-Tube Element (definition, structure, function)

*Definition:* In plants, an elongated sugar- conducting cell in phloem that lacks nuclei and has sieve plates at both ends, allowing sap to flow to adjacent cells. *Structure:* Are long, thin cells that have perforated ends called sieve plates. They lack nuclei and most other organelles, but they are directly connected to adjacent companion cells by means of numerous plasmodesmata. They are alive at maturity and lack secondary cell walls. *Function:* They are responsible for transport- ing sugars and other nutrients.

Primary Growth (definition, other)

*Definition:* In plants, an increase in the length of stems and roots due to the activity of apical meristems. *Other:* - The division of apical meristem cells, and differentiation of those cells, is responsible for primary growth, which is common to all plants. - The major consequence of primary growth is to increase the length of the root and shoot systems. - All of the cells and tissues that are derived directly from apical meristems constitute the primary plant body. - In general, most plants that do not produce woody tissues consist entirely of primary growth. - The dermal, ground, and vascular tissue systems are derived from cells in primary meristems, which originated from apical meristems. Thus, they represent primary growth and the primary plant body.

Secondary Growth (definition, other)

*Definition:* In plants, an increase in the width of stems and roots due to the activity of a cambium. *Other:* - In trees and other woody plants, secondary growth increases the width of roots and shoots. Its major function is to increase the amount of conducting tissue available and provide the structural support required for extensive growth. - Without the support provided by secondary growth, roots would not be massive enough to anchor large shoot systems, and long stems would fall over or break. Only with the origin of secondary growth could vascular plants become the giants seen today.

Primary Meristems (definition, types, other)

*Definition:* In plants, three types of partially differentiated cells that are produced by apical meristems, including protoderm, ground meristem, and procambium. *Types:* protoderm, ground meristem, and procambium. *Other:* - These regions are partially differentiated but retain the character of meristematic cells because they keep dividing. - The three types of primary meristems are important because they give rise to the dermal, ground, and vascular tissue systems

Vascular Tissue System (definition, function, tissue types)

*Definition:* In plants, tissues that transport water, nutrients, and sugars. Made up of the complex tissues xylem and phloem, each of which contains several cell types. *Function:* functions in support and in long- distance transport of water and dissolved nutrients in vascular plants. It also moves the products of photosynthesis that are made and stored in ground tissue. *Tissue Types:* Xylem, Phloem

Tracheid (definition, structure, other)

*Definition:* In vascular plants, a long, thin, water-conducting cell that has pits where its lignin-containing secondary cell wall is absent, allowing water movement between adjacent cells. *Structure:* Tracheids are long, slender cells with tapered ends. The sides and ends of tracheids have pits, which are gaps in the secondary cell wall where only the primary cell wall is present. Tracheids and vessel elements are often formed adjacent to each other. *Mechanism:* When water is moving up a plant through tracheids, it moves from cell to cell both vertically and laterally through pits, because that is where resistance to flow is lowest. *Other:* tracheids and vessel elements—like sclerenchyma cells—are dead at maturity and contain no cytoplasm.

Vessel Element (definition, structure, mechanism, other)

*Definition:* In vascular plants, a short, wide, water-conducting cell that has gaps through both the primary and secondary cell walls, allowing unimpeded passage of water between adjacent cells. *Structure:* Vessel elements, in contrast, are shorter and wider than tracheids. In addition to having pits, vessel elements have perforations—openings in the end walls that lack both primary and secondary cell walls. *Mechanism:* Vessel elements conduct water more efficiently than do tracheids, because their width and perfora- tions offer less resistance to flow. *Other:* tracheids and vessel elements—like sclerenchyma cells—are dead at maturity and contain no cytoplasm.

Ground Tissue System (definition, function, tissues)

*Definition:* Most common of the tissue systems; includes the following tissues/cell types: parenchyma, collenchyma, and sclerenchyma—tissues other than the epidermis and vascular tissue. *Function:* Photosynthesis and carbohydrate storage. Synthesis and storage of specialized products such as colorful pigments, hormones, and toxins required for defense. Some ground tissue cells also play a large role in structural support of the shoot system. *Tissues:* parenchyma (pronounced pa-REN-ki-ma), collenchyma (ko-LEN- ki-ma), and sclerenchyma (skle-REN-ki-ma).

Plasmodesmata (singular plasmodesma) (definition, other)

*Definition:* Physical connections between two plant cells, consisting of membrane-lined gaps in the cell walls through which the cells' plasma membranes, cytoplasm, and smooth ER can connect directly. Functionally similar to gap junctions in animal cells. *Other:* Plasmodesmata consist of cytoplasm and segments of smooth endoplasmic reticulum (smooth ER) that run through tiny, membrane-lined gaps in the cell wall.

Shoot System (definition, other)

*Definition:* The aboveground part of a plant comprising stems, leaves, and flowers (in angiosperms). *Other:* - The aboveground portion called the shoot system harvests light and carbon dioxide from the atmosphere to produce sugars. - Both Root and Shoot systems grow throughout the life of the individual, allowing the plant to increase in size, acquire resources, and reproduce. - Vascular tissue connects the root and shoot systems. Through vascular tissue, water and nutrients are transported from roots to shoots; sugars can be transported in both directions. - Root and shoot systems both function in absorption — roots absorb water and key nutrients, and shoots absorb light. the absorptive regions of a root system are tubelike, and the absorptive regions of a shoot system are flattened structures called leaves. - Absorption takes place across a surface. The cells that use the absorbed molecules and light occupy volume. A plant body is more efficient as an absorption and synthesis machine when it has a large surface area relative to its volume.

Root System (definition, other)

*Definition:* The belowground part of a plant. *Other:* - Anchors the plant and takes in water and nutrients from the soil. - Both Root and Shoot systems grow throughout the life of the individual, allowing the plant to increase in size, acquire resources, and reproduce. - Vascular tissue connects the root and shoot systems. Through vascular tissue, water and nutrients are transported from roots to shoots; sugars can be transported in both directions. - Root and shoot systems both function in absorption — roots absorb water and key nutrients, and shoots absorb light. the absorptive regions of a root system are tubelike, and the absorptive regions of a shoot system are flattened structures called leaves. - Absorption takes place across a surface. The cells that use the absorbed molecules and light occupy volume. A plant body is more efficient as an absorption and synthesis machine when it has a large surface area relative to its volume. - The roots of trees routinely extend beyond the width of their aboveground canopy. - It isn't unusual for a plant's root system to represent over 80% of its total mass.

Leaf (definition, other)

*Definition:* The main photosynthetic organ of vascular plants. *Other:* The defining feature of an individual leaf (whether simple or compound) is the presence of an axillary bud where the petiole joins the stem

Epidermis (definition, structure, function)

*Definition:* The outermost layer of cells of any multicellular organism. *Structure:* The epidermis is made up of several different cell types, and therefore represents a complex tissue. Complex tissue consisting of epidermal cells, guard cells, trichomes, and root hairs. Most shoot epidermal cells are flattened and usually lack chloroplasts. *Function:* Its primary function in shoots is to protect the plant—from water loss, disease-causing agents, and herbivores. In roots the epidermis includes root hairs, and it functions primarily in absorbing water and nutrients. - Shoots: protection, gas exchange. - Roots: protection, water and nutrient absorption.

Dermal Tissue System (definition, structure, function)

*Definition:* The tissue forming the outer layer of a plant; also called epidermis. *Structure:* Consists of dermal tissue. This tissue, also called the epidermis, is the outer- most layer of cells and represents the interface between the organism and the external environment. *Function:* Its primary function in shoots is to protect the plant—from water loss, disease-causing agents, and herbivores. In roots the epidermis includes root hairs, and it functions primarily in absorbing water and nutrients.

Phenotypic Plasticity (definition, other)

*Definition:* Within-species variation in phenotype that is due to differences in environmental conditions. Occurs more commonly in plants than animals. *Other:* - Phenotypic plasticity is particularly important in plants because they grow throughout their lives, and sometimes their environment changes. Roots actively grow into areas of soil where resources are abundant, such as nutrient-rich septic fields or sewer pipes that leak human waste. Roots stop growing or die back in areas where resources are used up or lacking. - The size and shape of an individual's shoot system can vary dramatically based on variation in growing conditions: temperature, exposure to wind, and availability of water, nutrients, and light. Because a plant's shoot system continues to grow over the course of its lifetime, it can respond to changes in environmental conditions just like the root system can.

Wood (definition, other)

*Definition:* Xylem resulting from secondary growth; forms strong supporting material. Also called secondary xylem. *Other:* Secondary growth produces wood and occurs only in species that have a cambium in addition to apical meristems.

Modified Leaves: Leaf functions other than photosynthesis

- *Nutrient Storage:* Onion bulbs consist of thickened leaf bases that store nutrients, separated by highly condensed internodes. - *Water Storage:* The thick leaves of plants called succulents, such as aloe vera, store water. - *Climbing:* The tendrils that enable plants, such as a grapevine, to climb are modified leaflets or leaves. - *Pollinator Attraction:* The bright red leaves of poinsettias attract pollinators to the tiny yellow flowers that they surround. - *Insect Trap:* The tubelike leaves of the pitcher plant trap insects. When insects enter, they feed on the plant's nectar and appear to become dizzy. Eventually they fall into the bottom of the tube and drown in water that has accumulated. The insects are then digested by bacteria or enzymes secreted by the plant, and the plant absorbs the nutrients released. - *Protection:* Cactus spines are modified leaves that protect the stem.

Explain how spores, pollen, stomata, cuticle, and vascular tissue helped plants adapt to life on land

- *Spores:* Allow plants to disperse progeny without water. - *Pollen:* Allow plants to deliver sperm without water. - *Stomata:* Allow plants to regulate gas exchange and water loss. - *Cuticle:* Prevents plant from drying out. - *Vascular tissue:* Allows plants to be upright and move water throughout their body.

How do plants get energy and nutrients?

- Photosynthesis: Plants use light energy to synthesize carbohydrates from carbon dioxide in the air and water from the soil. For photosynthesis to occur efficiently, plants need large amounts of light, carbon dioxide, and water. - Nutrients: To synthesize nucleic acids, enzymes, phospholipids, and the other molecules needed to build and maintain cells, plants must obtain nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and a host of other nutrients. Most of these key elements exist in nature as ions dissolved in water found in soil.

Shoot Morphological Diversity

- Variation in the size and shape of the shoot system is important: It allows plants of different species to harvest light at different locations and thus minimize competition. It also allows plants to thrive in a wide array of habitats. - Biologists interpret this diversity of shoot systems as a suite of adaptations for harvesting light and carbon dioxide in different environments: • In lush habitats, where competition for light is intense, woody individuals that grow tall are favored by natural selection. • In dry, windblown habitats, individuals with short stems or rosettes thrive because they require less water than taller individuals, and they don't blow over.

What structures do only plants have?

1. Primary and Secondary Cell Walls 2. Plasmodesmata 3. Chloroplasts 4. Vacuoles.

Tissue System (definition)

A broad category including tissues and cell types formed by the primary meristems (protoderm, ground meristem, procambium).

Apical Bud (definition)

A bud at the tip of a stem or branch, where growth occurs to lengthen the stem or branch.

Auxiliary Bud (Lateral Bud) (definition)

A bud that forms at a node and may develop into a lateral (side) branch. Also called lateral bud.

Lignin (definition)

A complex polymer built from six-carbon rings and found in the secondary cell walls of some plants; it is exceptionally stiff and strong. Most abundant in woody plant parts.

Tissue (definition)

A group of cells that function as a unit, such as muscle tissue in an animal or xylem tissue in a plant.

Root Apical Meristem (RAM) (definition)

A group of undifferentiated cells at the tip of a plant root; these cells divide to produce new cells that differentiate into mature root tissue.

Shoot Apical Meristem (SAM) (definition)

A group of undifferentiated cells at the tip of a plant stem; these cells divide to produce new cells that can differentiate into mature shoot tissues.

Taproot (definition)

A large, vertical main root of a plant's root system.

Indeterminate Growth (definition)

A pattern of growth in which an individual continues to increase its overall body size throughout its life.

Lateral Roots (definition)

A plant root that extends horizontally from another root.

Primary Meristem: Procambium (definition, other)

A primary meristem tissue that gives rise to the vascular tissue. *Other:* Vascular tissue runs through ground tissue, so the cells that make up ground tissue are usually close to cells that conduct the water and nutrients they need.

Adventitious Root (definition)

A root that develops from a plant's shoot system instead of from the plant's root system.

Cellulose (definition)

A structural polysaccharide composed of glucose monomers joined by β-1,4-glycosidic linkages. Found in the cell walls of algae, plants, and some bacteria and fungi.

Simple Tissue (definition)

A tissue consisting of a single cell type.

Complex Tissue (definition)

A tissue consisting of two or more cell types.

Anchor Roots (loose definition / function)

An adventitious root. They anchor stems to walls and to other plants.

Prop Roots (loose definition / function)

An adventitious root. They stabilize the stem.

Cell Sap (definition)

An aqueous solution found in the vacuoles of plant cells.

Ground Tissue (definition)

An embryonic tissue layer that gives rise to parenchyma, collenchyma, and sclerenchyma—tissues other than the epidermis and vascular tissue. Also called ground tissue system.

Primary Meristem: Ground Meristem (definition)

An embryonic tissue layer that gives rise to the ground tissue system which makes up the bulk of the primary plant body.

Totipotent (definition)

Capable of dividing and developing to form a complete, mature organism.

Perennial (definition)

Describing a plant whose life cycle normally lasts for more than one year.

Ground Tissue System: Cortex (definition)

In plants, a layer of ground tissue found outside the vascu- lar bundles of roots and outside the pith of a stem.

Callus (definition)

In plants, a mass of undifferentiated cells that can generate roots and other tissues necessary to create a mature plant.

Sieve Plate (definition)

In plants, a pore-containing structure at each end of a sieve-tube element in phloem.

Perforation (definition)

In plants, a small hole in the primary and secondary cell walls of vessel elements that allows passage of water.

Pit (definition)

In plants, a small hole in the secondary cell walls of tracheids and vessel elements that allows passage of water.

Leaf Plasticity: Sun vs. Shade Growth

Leaves grown in the sun is much smaller than the leaf grown in the shade: • *Sunned leaves:* typically are thicker and have a relatively small surface area, which reduces water loss in areas of the body where light is abundant. • *Shaded leaves:* are relatively thin and broad, providing a high surface area that maximizes absorption of rare photons. Water loss is less of a problem for shade leaves because temperatures are cooler in shade than in bright sun.

Transpiration (definition)

Loss of water vapor from aboveground plant parts. Occurs primarily through stomata.

Water Storage Stem Structures (loose definition, example)

Modified stems. Cactus stems store water; the spines are modified leaves. Instead of functioning primarily to support leaves, cactus stems often enlarge into water-storage organs. Water accounts for up to 98 percent of the weight of a cactus stem. Cactus stems also contain the plant's photosynthetic tissue.

Do plant cells move position during development?

No. It is an important distinction between plant cells and animal cells. Plant cells do not change position once they form. Some animal cells migrate within the body either early in the development of an individual or as mature (differentiated) cells but plant cells stay put.

Guard Cell (definition)

One of two specialized, crescent-shaped cells forming the border of a plant stoma. Guard cells can change shape to open or close the stoma.

What structures/characteristics are shared by both plant and animal cells?

Plants and animals, share most of their key characteristics: chromosomes enclosed in a nuclear envelope, a plasma membrane studded with proteins that regulate the passage of materials in and out, mitochondria that produce ATP by oxidizing sugars, and an array of other organelles that synthesize or degrade key molecules.

Pneumatophores (function)

Pneumatophores allow gas exchange between roots and atmosphere

Herbaceous (definition)

Referring to a plant that is not woody.

Biennial (definition)

Referring to a plant whose cycle lasts two years. Ex: carrots.

Annual (definition)

Referring to a plant whose life cycle normally lasts only one growing season—less than one year.

Fibrous Root System (loose definition)

Roots with are a thick mat of slender roots spreading out below the soil surface. They are not as deep as taproots.

Spongy Mesophyll (definition)

Spongy mesophyll is irregularly shaped and not as tightly packed, allowing for leaf air spaces to form in the leaves.

Leaf Arrangements

The arrangement of leaves on a stem can vary as much as leaf shape. For example, leaves can be: • Arranged to alternate on either side of the stem. • Paired opposite each other on the stem. • Arranged in a whorl. • Found in a compact arrangement where internodes are extremely short—leading to a rosette growth form.

Primary Meristem: Protoderm (definition)

The exterior layer of a young plant embryo that gives rise to the dermal tissue, or epidermis.

Primary Cell Wall (definition)

The outermost layer of a plant cell wall, made of cellulose fibers and gelatinous polysaccharides, that defines the shape of the cell and with-stands the turgor pressure of the plasma membrane.

Palisade Mesophyll (definition)

The palisade cells are near the top and vertically elongated. Palisade mesophyll chloroplasts absorb a major portion of the light energy used by a leaf.

Internode (definition)

The section of a plant stem between two nodes (sites where leaves attach).

Petiole (definition)

The stalk of a leaf.

Describe two morphological adaptations that plants may have to water-limiting environments. How does each work?

The surface of the leaf may have hairs which create a boundary layer in which humidity is increased and air movement is decreased near the surface of the leaf, so the water potential gradient between the inside of the leaf and the immediate outside of the leaf is reduced. Stomata may be sunken or found in crypts, so that the air directly outside of the stomata has an increased water potential, again minimizing the gradient between the inside and outside of the leaf.

Secondary Cell Wall (definition)

The thickened inner layer of a cell wall formed by certain plant cells as they mature and after they have stopped growing; contains lignin in water-conducting cells. Provides support or protection.

Blade (definition)

The wide, flat part of a plant leaf.

Storage Roots (function)

They store carbohydrates and other nutrients in their taproot for future use. Ex: sugar beets.

Stems (definition)

Vertical, aboveground structures that make up the shoot system of plants.

Shoot System Structures

• The shoot system consists of one or more stems, which are vertical aboveground structures. • A stem consists of nodes, where leaves are attached, and internodes, or segments between nodes. • A leaf is an appendage that projects from a stem laterally. Leaves usually function as photosynthetic organs. • The nodes where leaves attach to the stem are also the site of axillary (or lateral) buds, which form just above the site of leaf attachment. • If conditions are appropriate, an axillary bud may grow into a branch—a lateral extension of the shoot system. • The tip of each stem and branch contains an apical bud, where growth occurs that extends the length of the stem or branch. • If conditions are appropriate, apical or axillary buds may develop into flowers or other reproductive structures.