Bio Chapter 35
Lateral Meristems
-2ndary growth -only in WOODY plants -growth in thickness -Vascular and Cork cambium -Vascular cambium adds layers of vascular tissue called 2ndary xylem (wood) and 2ndary phloem -Cork cambium replaces the epidermis w/thicker, tougher periderm
Annual, Biennial, and Perennial Plants
-Annual: plants that complete a life cycle in 1 year (ex. legumes, wildflowers, wheat) -Biennial: require 2 growing seasons to complete their life cycle, flowering and fruiting in the 2nd (ex. turnips) -Perennials: live many years (ex. trees, shrubs)
Monocot Stem
-Ground tissue not split into pith and cortex -Vascular bundles are scattered
Sclerenchyma Cells
-Have primary and 2ndary cells walls (thick, a lot of lignin) -important in support -2 forms: sclereids (nutshells, seed coats, and pears) and fibers, specialized for support and strengthening -Found in areas where growth has stopped -Can be dead, but still be used for support
Monocot Root
-Parenchyma in center -Stele is a vascular cylinder with a core of parenchyma surrounded by a ring of xylem and ring of phloem -Phloem still external to Xylem Inner to Outer: Core of Parenchyma Cells, Xylem, Phloem, Pericycle, Endodermis, Cortex, Epidermis
Eudicot Stem
-Pith is ground tissue toward the inside -Cortex is ground tissue toward the outside -Phloem still external to Xylem -Vascular bundles form a ring Inner to Outer: Pith, Xylem, Phloem, Sclerenchyma Cells, Cortex, Epidermis
Rhizoids vs. Rhizomes
-Rhizoids: a long, tubular single cell or filaments of cells that anchors bryophytes to the ground, not composed of tissues, lack specialized conducting cells, and don't absorb water and minerals -Rhizome: a horizantal shoot that grows just below the surface
Collenchyma Cells
-Rigid primary cell walls, no 2ndary -important in young plants and non-woody plants -capable of elongation -no lignin -provide flexible support w/o restraining growth
Primary Growth of a Root
-Root Cap: protects apical meristem, also secretes a slime that lubricates the soil around the tip, helps mature the soil -Zone of Differentiation: root hairs, increases surface area, cells complete their differentiation and become distinct types -Zone of Elongation: where most of the growth occurs as root cells elongate, pushes the tip farther into the soil -Zone of Cell Division: includes root apical meristem and its derivatives
Eudicot Leaf
-Stomata: allow exchange of CO2 and O2, evaporative water loss occurs, flanked by 2 guard cells which regulate opening and closing of the pore -Mesophyll: ground tissue of leaf, between upper and lower epidermal layers, consists of parenchyma cells for PHOTOSYNTHESIS -Palisade Mesophyll: upper part of leaf -Spongy Mesophyll: below the palisade region -Veins: where vascular system is, bundle sheath cells protect vein -Cuticle
Different Types of Roots
-Taproots: the main vertical root, develops from an embryonic root -Fibrous Roots: a mat of generally thin roots spreading out below the soil surface, best for shallow soils or light rainfall regions -Adventitious Roots: when many small roots emerge from the stem
Parenchyma Cells
-Thin, flexible primary cell walls, no 2ndary -found everywhere in plants -relatively unspecialized -have water, large central vacuole, and can carry nutrients -does most of metabolic activity in plants, synthesizes and stores various organic products -important in repair and replacement -can store starch
Water Conducting Cells of the Xylem
-Tracheids: long and ting with tapered ends, water moves from cell to cell via pits -Vessel Elements: wider, shorter, thinner walled, and less tapered. Aligned end to end forming vessels, the end walls of vessel elements have perforation plates that enable water to flow freely -tubular, elongated cells that are dead at functional maturity -are like channels that carry water -dead except cell wall
Eudicot Root
-Xylem and Phloem in center -Xylem is cross shaped assortment -Phloem external to Xylem -Stele is a vascular cylinder appearing in core section as a lobed core of xylem with phloem in between lobes Inner to Outer: Xylem, Phloem, Pericycle, Endodermis, Cortex, Epidermis
Cuticle
-a waxy coating on the epidermal surface -helps prevent water loss -The waxy cuticle of the aerial parts of a plant prevents excessive water loss by retaining water, whereas it would serve no purpose in a root system where its primary function is water uptake.
Sugar Conducting Cells of the Phloem
-are alive -Seedless Vascular plants and Gymnosperms: sugars and other materials transported through SIEVE CELLS -Angiosperms: these nutrients are transported thru sieve tubes, which consists of chains of cells called sieve-tube elements -Sieve-tube elements are "brain dead" b/c they lack a nucleus, ribosomes, vacuole, and cytoskeletal elements -Sieve plates are end walls btwn sieve-tube elements, they have pores that facilitate flow of fluid -Companion Cell: a nonconducting cell alongside each element, which is connected to the element by plasmodesmata
Plant Growth
-capable of growth b/c of meristems that divide, leading to new cells that can elongate
Indeterminate Growth
-growing for your entire life
Secondary Growth
-increases diameter of steams and roots in woody plants but not leaves -consists of tissues produced by vascular cambium and cork cambium -Vascular cambium adds secondary xylem (wood) and phloem -Cork cambium produces a tough, thick covering consisting of waxed cells that protext stem from water loss and invasion -2ndary growth rare in monocots
Endodermis
-innermost layer of the cortex -forms the boundary with the vascular cylinder -a selective barrier that regulates passage of substances from the soil into the vascular cylinder
Apical Meristem
-located at tips of roots and shoots and in axillary buds -provide additional cells that enable growth in length -Primary Growth -allows roots to extend throughout soil and shoots to increase their exposure to light
Meristematic Tissue
-needed for growth -Protoderm -> dermal tissue -Precambium -> vascular tissue -Ground Meristem -> ground tissue
Dermal Tissue System
-plant's outer protective covering -1st line of defense -usually a single tissue called epidermis (non-woody) -Cuticle -In woody plants, the PERIDERM replaces the epidermis
Woody Plant Stem
-see pg. 752 -Spring Wood: wood that develops earn in the spring, consists of 2ndary xylem cells with large diameters and thin cell walls allowing max delivery of water to new leaves -Summer Wood: wood produced in the rest of hte season, composed of thick-walled cells that provide more support but not as much transport of water -Heartwood: older layers of 2ndary xylem that no longer transport water as the plant ages, closer to the center of the stem or root -Sapwood: the newest, outer layers of 2ndary xylem that still transport xylem sap -Rays: radial files of parenchyma cells that connect 2ndary xylem and phloem, move water and nutrients btwn the 2, carbo storage, wound repair -Lenticles: small, raised areas that dot the periderm, more space btwn cork cells, allowing living cells to exchange gases with outside air -Periderm: protective tissues that replace the epidermis in older regions of stems and roots -Bark: all tissues external to the vascular cambium (secondary, living phloem + periderm), more than just whats on outside
Vascular Tissue System
-transport and support -xylem and phloem -Stele: what the vascular tissue of a root or stem is collectively called
Ground Tissue System
-usually parenchyma cells -can be used for storage, support, and photosynthesis -Pith: ground tissue internal to the vascular tissue -Cortex: ground tissue that is external to vascular tissue
Pericycle
-where lateral roots arise from -outermost layer in the vascular cylinder, adjacent to and just inside endodermis
Land Plant structure
Root System -taproot -lateral (branch) roots Shoot System -Reproductive Shoot (flower) -Vegetative Shoot -Apical Bud: where growth of young shoot is concentrated and Axillary Bud: can from a lateral shoot (branch) -Node: points where leaves are attached and Internode: stem segments between nodes -Leaf (Blade and Petiole) -Stem: an organ that raises or separates leaves, exposing them to sunlight
