BIO 305 Study Guide - Exam 1

True/False The 'Cell Theory" was developed by Charles Darwin and Gregor Mendel.

False Developed by Matthias Schleiden, Theodor Schwann, and Rudolph Virchow

What factors, or mechanisms, have been identified as causing coat-imposed dormancy of seeds?

seed coat plays an important role in causing the dormancy of the seed. The seed coat or testa is composed of several laylers of cells and is composed of polysaccharides, hemicellulose, fats, waxes, and proteins. During seed ripening the chemical components of seed coat become dehydrated and form a hard tough protective layer around the embryo. Due to impermeability of seed coat, the germination of seed is delayed. The hard seed coat prevents seed germination in 3 ways. 1. By preventing the entry of water into the seed. Seeds of many plants are impermeable to water due to hard seed coats. 2. By interfering with exchange of gases. The seed coats some seeds area permeable to water but impermeable to oxygen. 3. By offering mechanical resistance for the growth of the radicle.

11. Distinguish between a centromere and a kinetochore.

- A centromere is a constricted region of highly specialized repetitive DNA sequences that is found on a chromosome. -A kinetochore is a protein complex that is associated with the centromere and assembles on it. Centromere - a center to which the chromatids are attached Kinetochore - is the center to which the spindle fibers are attached. During cell division: Kinetochores are attached to the microtubules along which the chromosomes travel Centromeres are not attached to these microtubules. Centromere - can be seen with light microscope. Kinetochores- can ONLY be seen via electron microscope.

4. Once regarded as depositories for waste products in plant cells, vacuoles now are known to play many different roles. What are some of those roles?

- The vacuoles serve as repositories of primary metabolites and proteins - They also are a store house of anthocyanins. - Apart from these functions, the macro-molecules that enter the cell in the form of vesicles, sometimes get fused with the vacuoles and thus are released in them. Here these macro-molecules undergo breakdown into simpler ones. - Further the organelles or macro-molecules that are not required by the cells are transported to the vacuoles where they undergo breakdown. Thus the vacuoles help in the recycling of chemical elements.

1. How is polarity important in embryonic development of plants?

1 sperm fertilizes the egg --> giving rise to 2n diploid zygote another sperm fertilizes a polar cell with 2 1N nuclei --> giving rise to a 3N triploid endosperm. the endosperm provides nutrients to the developing embryo. Plant embryogenesis begins with asymmetric cell division. a Small apical cell and a large basal cell. The apical cell is most of the plant develops from, the large basal cell is what the suspensor develops from.

2. What three features of plant cells distinguish them from animal cells?

1) Plant cells have cell wall made up of cellulose as their outermost layer. Plant cells have fixed shaped and are mostly rectangular. Animal cells have cell membrane as their outermost layer. Animal cells do not have a rigid structure and are mostly circular or oval. 2) Plant cells have a single large vacuole that covers almost 90% of the cell space. Animal cells have two or more small vacuoles. 3) Plant cells have chloroplasts that give the plants a green color and thus are capable of making their own food. animal cells do not have chloroplasts and thus cannot make their own food.

2. What are the various types of plastids that are found in a plant cell, and what role(s) does each play in the cell?

1. Chloroplasts 2. Chromoplasts 3. Leucoplasts 1. Chloroplasts are the principal plastids that are present in large numbers in a plant. though these plastids contain both chlorophyll and carotenoid pigments but due to the presence of large number of chlorophyll pigments that are green in color, the other carotenoid pigments get masked. It is because of these plastids that the leaves get their green color. These chloroplasts are also the site of photosynthesis and thus are the sites where food and energy in the form of ATP is produced. These plastids are also involved in the synthesis of fatty acids, secondary metabolites and amino acids. 2. Chromoplasts are pigmented plastids like chloroplasts but Lack the pigment chlorophyll. They synthesize and retain the carotenoids and thus are the pigments that are responsible for the various colors of flowers, fruits, aging leaves and some roots. 3. Leucoplasts are plastids that lack pigments and are less differentiated than the rest of the plastids. A special kind of leucoplasts called amyloplasts is known to synthesize starch. Other functions of leucoplasts include generation of oils and proteins.

8. What is the probable role of P-protein in mature sieve-tube elements?

A sieve tube elemnt develops form a meristematic initial cell having a prominent nucleus and dense cytoplasm. In dicots, the sieve tubes composed of a viscous proteinaceous substance called slime appears in the form of discrete bodies. This substance has been re-named as P-protein. The deposition of P-protein on a sieve area is called slime plug. It is an indication that the sieve element has been injured. At the time of injury, P-protein seals the sieve element pores and prevents the leaking of components from sieve elements.

4. How do simple tissues differ from complex tissues? Give examples of each.

A simple tissue is made up of a similar permanent cells that carry out the same function or similar set of functions. Simple tissues are of three types namely parenchyma, collenchymas, and scelrenchyma. The permanent tissues which contain more than one type of cells and work as a unit are called complex tissues. The common complex tissues are conducting tissues, xylem, and phloem.

1. What is a meristem, and what is its composition?

A tissue which consists of active dividing cells or the cells having power of cell division is called the meristem or merstematic tissue. The component cells of merstems have ability to divide. The meristematic cells are small in size and almost isodiametric with prominent nucleus and dense cytoplasm and they lack intercellular spaces. They have thin and elastic cell walls that are made up of cellulose. This tissue is confined to growing regions of plant body.

5. What phenomena, or processes, characterize seed maturation, the second phase of seed development?

After embryogeny, seed enters into the Seed Maturation, the second phase of seed development. During this period, the developing seed accumulate the large quantities of food materials such as polysaccharides, hemicelluloses, fats, waxes, and some storage proteins, which are needed for further seed germination process. At this same stage, the developing seed loses more than 90% of its water to the surrounding environment due to desiccation. Desiccation is the process between maturation and germination. It is followed by the chemical components of seed coat as it becomes dehydrated and forms a hard tough protective layer around the embryo. Due to impermeability of seed coat, the germination of seed is delayed.

4. How do parenchyma, collenchyma, and sclerenchyma cells differ from one another? What are their respective functions?

All parenchyma, collenchyma and sclerenchyma tissues are belong to simple permanent tissues. Parenchyma, collenchyma tissues are made up of living and thin walled cells, whereas sclerenchyma made up of dead and thick walled cells. PARENCHYMA - The parenchyma tissues consist of group of isodiametric or oval shaped cells and are loosely arranged with intercellular spaces. The cells of parenchyma contain cytoplasm, vacuole, and prominent nucleus. It is the most simple and primitive tissue. FUNCTIONS: The main function of parenchyma tissue is storage of food and it is helps in storage of water in some plants like xerophytes. COLLENCHYMA: The cells of collenchyma are smaller in size than parenchyma but like parenchyma; contain cytoplasm, vacuole and nucleus. Intercellular spaces are absent. FUNCTIONS: The collenchyma's main function is to provide flexibile mechanical support and tensile strength to the organs. SCLERENCHYMA: It is made up of thick walled cells without intercellular spaces and thickening is due to deposition of lignin and they become hard and elastic. They lack a nucleus and cytoplasm at maturity and hence dead. They are generally divided into two categories namely fibers and sclerids. FUNCTIOS: The main function of sclerenchyma is to provide mechanical strength and rigidity to the plant body.

During cell division, chromosomes move toward the poles during which phase?

Anaphase

Organism that can make their own food are called ________ ??

Autotrophs

12. What is the preprophase band? What role does it play in plant cell division?

Band of microtubules that is formed just before the start of mitosis. It is formed as a band of microtubules and some actin filaments around the phragmosome and the place where the cell would be divided after the mitosis, just below the plasma membrane. The most important role of the prephrophase band is that it marks the location where the new cell plate will be formed after the telophase of the mitosis. Also since plant cells lack centrosomes, thus the microtubules from the preprophase band help in formation of spindle fibers and in the proper orientation of the spindle fibers in the mitosis.

3. Both plastids and mitochondria are said to be "semiautonomous" organelles. What does this mean?

Both plastids and mitochondria contain their own DNA and have the ability to replicate or divide by themselves. they are semi autonomous and not completely autonomous because though they can replicate independently, for the other requirements to carry out the cell reactions they depend upon the nucleus. Thus they are semi autonomous.

6. What is the developmental and/or functional relationship between a sieve-tube element and its companion cell(s)?

Both sieve tube elements and companion cells are components of phloem. Sieve tubes are associated with companion cells. Both cells are arising from the same mother cell. Companion cells are thin walled usually attached to the lateral side of sieve tube by means of simple pits, and they originate from the same meristematic cells that give rise to the sieve tube element. These cells help in transport of food along with sieve tubes. The nucleus of companion cells controls the functioning of sieve tube.

True/False "9+2" flagella are not found in any plants.

False

What type of plastid stores carotenoid pigments, for example, (Beta)-Carotene in carrot roots?

Chromoplast

1. Distinguish between the following: collenchyma cell and sclerenchyma cell; tracheid and vessel element; perforation plate and pit; sieve cell and sieve-tube element; callose and P-protein.

Collenchyma - tissue is composed of narrow, elongated cells with thick primary walls. Provide structural support to the growing plant body, particularly shoots, and their thickened walls are non lignified, so they can stretch as the organ elongates. Collenchyma cells are typically arranged in bundles or layers near the periphery of stems or leaf petioles Parenchyma - the most abundant ground tissue, consists of thin-walled, metabolically active cells that carry out a variety of functions in the plant, including photosynthesis and storage Sclerenchyma - consists of two types of cells, sclereids and fibers. Both have thick secondary walls and are frequently dead at maturity. Sclereids occur in a variety of shapes, ranging from roughly spherical to branched, and are widely distributed throughout the plant. In contrast, fibers are narrow, elongated cells that are commonly associated with vascular tissues. The main function of sclerenchyma is to provide mechanical support, particularly to parts of the plant that are no longer elongating. Tracheid & Vessel Element: conducting cells of the xylem. Both of these cell types have elaborate secondary-wall thickenings and lose their cytoplasm at maturity; that is, they are dead when functional. Tracheids overlap each other, whereas vessel elements have open end walls and are arranged end to end to form a larger unit called a vessel. sieve-tube element & sieve cells: are responsible for sugar translocation in the phloem. The elements are found in angiosperms; and the cells perform the same function in gymnosperms. Like vessel elements, sieve elements are often stacked in vertical rows, forming larger units called sieve tubes, whereas sieve cells form overlapping arrays. Both types of conducting cells are living when functional, but they lack nuclei and central vacuoles and have relatively few cytoplasmic organelles

Robert Hooke coined the word "cell" based on his observations of ?

Cork

8. What is cytokinesis, and what roles do the phragmosome, the phragmoplast, and the cell plate play during the process?

Cytokineses is the division of cytoplasm that occurs at the end of mitosis. Phragmoplast is barrel shaped structure made up of microtubules that forms during the early telophase. It also contain actin filaments and these along with the microtubules form two arrays on the opposite sides of the division plane. The cell plate is present as a suspended structure in the phragmoplast. The phragmoplast starts dividing along with the cell plate until it reaches the cell wall of the dividing cell. Once the cell place is completely formed, the phragmoplast microtubules disappear. Cells that have large vacuoles have phragmosomes within which the cell plate and phragmoplast are formed.

2. Describe the three overlapping processes of plant development and the way they overlap.

Development is the sum total of growth and differentiation. It is influenced by both extrinsic and intrinsic factors. The development of plant involves the three overlapping processing namely, growth, morphogenesis, and differentiation. GROWTH: It is one of the characteristic features of living organisms. Growth is a vital process, which brings about irreversible increase in any organism or its part with respect to its size, shape, volume, and dry weight. Plant growth takes place in three steps or phases-cell division phase, enlargement phase, and maturation phase. MORPHOGENESIS: It is the formation of different tissues and organs like root, shoot, and leave. At this stage a plant gets a particular shape. DIFFERENTIATION: It is the permanent qualitative change in structure, chemistry, and physiology of cell wall and protoplasm of cells and their tissues and organs. It is caused by repression of genes.

6. Of what significance is seed dormancy to a plant?

Dormancy =growth is temporarily suspended. The main purpose of dormancy is to enable the plant endure unfavorable conditions. Thus it provides a mechanism of survival. Dormancy of seeds is useful to human beings because they can harvest, store and use the grains as food.

What is dormancy? What occurs within a seed when it germinates? What roles do specific hormones play in: a) promoting and maintaining dormancy and b) in overcoming dormancy and allowing germination to occur?

Dormancy is when the seed temporarily stops growth. The seed dehydrates (loses most of its water). It is promoted by and maintained by ABSEISIC ACID, a hormone.

5. Explain the phenomenon of autumn leaf coloration.

During summer, the rate of photosynthesis remains almost constant due to optimal environmental conditions for photosynthesis. Thus chlorophyll pigments remain active and help in maintaining the green color of the leaf as they are numerous in numbers as compared to the other pigments. In late summers, as the temp decreases and the amount of sunlight available to the plant decreases, a layer of cork begins to form at the base of leaves. As this layer of cork increases, it affects the flow of nutrients and water to the leaves. As a result, the rate of photosynthesis is affected and thus chlorophyll pigments reduce in number. Now the other pigments such as anthocyanins, Carotenoids and xanthophylls are able to exhibit their colors. Thus the color of the leaf changes to the color of the most abundant pigment in the late summers or during autumn.

True/False Plant cells never contain mitochondria; they contain chloroplasts instead

False

True/False Plant cells usually elongate parallel to the axis in which interphase MTs are aligned.

False

3. Through what stages do embryos of eudicots develop? How does embryo development in monocots differ from that in eudicots?

Embryo development in eudicots: After fertilization the zygote divides transversely to form a large basal cell or suspensor cell towards the micropyle and a small apical cell towards interior of embryosac. From this 2-celled stage, the organs are formed by series of divisions, which is called as proembryo. T apical cell of the 2 celled pro embryos undergoes transverse and two vertical divisions at right angles to each other to form an octant stage. The eight cells of octant pro embryo undergo many divisions to form a spherical mass of cells. Gradually this mass becomes heart shaped and then horse shoe shaped. Finally, it gets differentiated to form an embryonal axis with plumule, radicle, and cotyledons. The development of embryo in monocots is similar to dicots until octant stage. In dicots, the two opposite cells are involved in the formation of octant whereas in monocots the number of cells involved varies from species to species. The main difference between mature embryos of dicots and monocots is the number of cotyledons.

__________ Is the evolutionary process by which chloroplasts become components of plant cells.

Endosymbiosis

2. What is meant by "growth"?

Growth is one of the characteristic features of living organisms. It is the permanent increase in size, shape, volume, and dry weight. The change due to growth is permanent and irreversible. It is an intrinsic process caused by internal activities. It occurs by cell division and cell elongation followed by cell maturation to form different types of tissues.

Turgor pressure within a cell will be high if the concentration of solutes inside of the cell is ??

Higher than the concentration outside

10. In the typical cell cycle there are checkpoints. What are these checkpoints? What purpose do they serve?

In a typical eukaryotic cell, there are certain control mechanisms that ensure that every process in the cell cycle has been completed accurately before a phase progresses to the next phase. these control mechanisms are called the checkpoints of the cell. Cell cycle checkpoints: The 1st checkpoint is at the end of the G1 phase, which either stops the cycle or initiates the S phase depending upon the accuracy of the G1 phase. The second checkpoint is at the end of the G2 phase, that either arrests the cycle or triggers the initiation of mitosis, again depending on the accuracy of the earlier phase.

9. In what sense do plants differ from animals with respect to the location of most cell division activity?

In plants, most of the cell division activity occurs at the apical meristems. The apical meristems are located at the apex of the plants like the auxiliary buds, main root tip and at the apex of the main stem. These meristematic cells are thus located in places called meristems which are specialized cells that undergo continuous division for the growth and elongation of the plant. In animals, until the growth into a full adult, cell division usually take place in all the cells. But in adults, the cell division and formation of new cells is primarily restricted to cells called stem cells. These stem cells are restricted to very few areas of the human body such as the bone marrow and umbilical cord.

How does the cortical array of MTs contribute to cell wall synthesis? What effect does this have on the direction of cell elongation?

In the Interphase Array, microtubules are perpendicular to the long axis of the cell. Microtubules control the orientation of cellulose in cell wall, which controls the direction of cell elongation.

4. What is the "cytoskeleton" of the cell, and with what cellular processes is it involved?

It is a 3D network of different protein filaments that are present throughout the cytoplasm. The cytoskeleton proteins are mainly made up of two types of protein filaments: Microtubules that are made of the protein tubulin and Microfilaments that are made up of the protein actin. The main function of the cytoskeleton include, formation of spindle fibers in cell division, proper alignment of chromosomes on the spindle fibers, help in growth of the cell, differentiation of various organelles and also the movement of organelles from one place to the other within a cell.

What is the evolutionary origin of chloroplasts?

Mitochondria and Chloroplasts evolved from phagocytized bacteria. (Phagocytes- capable of engulfing large particles such as bacteria.)

Can you accurately draw an embryo at the heart stage of development and label all of the tissue types, meristems and other organs that are present?

No.

Distinguish among or between the following: proembryo, embryo proper, and suspensor; globular stage, heart stage, and torpedo stage; epicotyl and plumule; hypocotyl-root axis and radicle; coleorhiza and coleoptile.

PRO EMBRYO: After fertilization, the zygote undergoes transverse division to form a 2 unequal cells, i.e, large basal cell and small apical cell. This 2 celled stage is called proembryo. SUSPENSOR: the zygote divides transversely to form a large basal cell towards micropyle and a small apical cell towards and interior of embryosac. The large basal cell divides transversely to form a row of cells which is called a suspensor. EMBRYO PROPER: The zygote divides transversely and results 2 celledpro embryo. The 2 cells are large basal cell and small apical cell. The basal cells now divides transversely while the terminal cell divides longitudinally and forms 4 celled proembryo. Now this 4 celled proembryo undergo a series of divisions and results the formation of embryo proper. The apical part of embryo proper is the initiation portion of protoderm. At the time of embryo development, the apical cell of the pro embryo undergoes a transverse and two vertical divisions at right angles to each other to form octant stage. The eight cell stage of octant pro embryo undergo many divisions to form a spherical mass of cells. This stage is called as GLOBULAR STAGE. At this stage embryo proper is spherical. Gradually, this mass gets lobed structures it becomes a HEART or CORDATE SHAPED. When the two cotyledons start differentiating and fully developed embryo bents and becomes a TORPEDEO or horse shoe shaped. the dicot embryo consists of embryo-axis and two cotyledons. The embryo axis consists of two ends-the radicle and plumule. The plumule later produces the shoot system. The part between plumule and cotyledons is called epicotyl. The dicot embryo consists of embryo-axis and two cotyledons. The embryo axis conssits of two ends-the radicle and plumule. The radicle former gives rise to root system. The cotyledons are attached to the embryo axis at the region, which represents first node of embryo. The part of embryo axis between radicle and first node is called hypocotyl. The monocot embryo consists of a single cotyledon and the axis. The upper portion of the axis is called plumule and the lower portion is the radicle. The plumule is surrounded by a protective sheath called as coleoptile and the radicle is surrounded by another sheath called coleorhiza.

____________ is the microtubule array that predicts where a new cell wall will form during cytokinesis.

Pre Prophase Band

2. What are the three primary meristems of plants, and which tissues do they form?

Primary meristems are primary in origin because it develops from embryonic tissues. The three primary meristems are Protoderm, Procambium, and Ground meristem. These are present in the growing regions. Here, protoderm is the outermost layer of growing region, which gives rise to epidermal tissue system in developing organs. The procambium is used for all those elongated cells, which may or may not be precursors of fascular elements. The ground tissue gives rise to hypodermis, cortex, endodermis, pericycle, medullary rays, and pith. All such parts together constitute the ground tissue system in plants.

1. How does the structure of a prokaryotic cell differ from that of a eukaryotic cell?

Prokaryotic cell smaller than eukaryotic cell. Prokaryotic cell varies from 1-20 micrometers. Eukaryotic cells vary between 5-100 micrometers. Some eukaryotic cells are even longer than 100 micrometers and are generally found in plants. Prokaryotic cell - NO nuclear envelop Eukaryotic cell - has a nucleus that is properly enclosed by a nuclear membrane. Prokaryotic cell - lacks membrane bound organelles Eukaryotic cells - possesses number of specialized membrane bound organelles that have characteristic functions. Prokaryotic cells structurally lack the presence of a cytoskeleton Eukaryotic cell - have a cytoskeleton that is made of microtubules and actin filaments.

What are the functions of various types of plastids? Where are they found? Can they be interconverted?

Proplastid are undifferentiated and are in meristematic cells. CHLOROPLASTS - responsible for photosynthesis. CHROMOPLAST - store carotenoid pigments in membranes, (red,orange,yellow pigments). AMYLOPLASTS- found in roots, cotyledons, tubers, fruits, and endosperms. They synthesize and store Starch Granules. When the plant needs energy, amyloplasts convert their stored starch into glucose - energy.

5. How do sclereids differ from fibers?

Sclerenchyma is a dead, simple permanent tissue made up of thick walled cells. Sclerenchyma is of two types, sclerenchyma fibers and sclerieds. Sclerenchyma fibers are highly elongated narrow and spindle shaped thick walled cells with pointed or obliquie end walls. The cell walls are evenly thickened due to deposition of lignin. It gives the mechanical strength. Sclerieds or stone cells are extremely thick walled, hard, and strongly lignified. They are mostly isodiametric or polyhedral with very small lumen. Sometimes, the cells are elongated and may be rod shaped, bone shaped or star shaped. They provide rigidity and strength.

What environmental factors are especially important for seed germination?

Seed imbibes water. Nutrients are mobilized. Stored polymers are degraded to release monomers. SAM and RAM are reactivated and cell division resumes. Water, nutrients in soil, and gibberellic acid (GA), a hormone that promotes germination. Chegg: External factors like water, temperature, oxygen, CO2, light inhibitors, and internal factors. These external factors are very important for seed germination.

Structures in the leaf epidermis that open and close to regulate gas exchange are ?

Stomata

6. Distinguish between rough endoplasmic reticulum and smooth endoplasmic reticulum, both structurally and functionally.

Structural Differences: The rough ER has ribosomes attached to it while the smooth ER does not. the rough ER is present as flattened sacs in the cell while the smooth ER is present as a network of interconnected tubules. The rough ER's are found in abundance near the nucleus and the Golgi while the smooth ER's are found almost evenly distributed throughout the cell. Functional Differences: Rough ER - protein synthesis in the ribosomes. Smooth ER - lipid synthesis. Rough ER is also involved in the quality check of manufactured proteins, transfer of proteins to the Golgi apparatus and storage of minerals and calcium. Smooth ER also serve in the breakdown of glycogen to glucose, production of steroid hormones and as a detoxification unit.

What role is played by the suspensor in angiosperms, and what evidence indicates that the embryo proper suppresses the embryonic pathway in the suspensor?

Suspensor is an ephemeral structure( meaning it lasts for a very short time) found at the radicular end of pro embryo. It anchors the embryo to the embryo sac and pushes it deep into the endosperm. The suspensor absorbs nutrients from various ovular regions.

7. Distinguish between microtubules and actin filaments. With what functions are each of these protein filaments associated?

The actin filaments structurally form a double helix and are smaller than microtubules in size. The microtubules have a helical lattice structure and are larger in size than the actin filaments. Actin filaments- mainly made up of actin fibers (contractile proteins). Microtubules - mainly composed of a protein called tubulin (two types-alpha and beta proteins). Structurally: Actin filaments are strong but flexible due to the presence of actin protein. Microtubules are structurally stiff and resist bending force. Main function: Actin filaments- cell or cytoplasmic movement Microtubules - cell divisions like mitosis and other cell transport. Main function in Plants: Actin filaments - cytoplasmic movement. Microtubules - chromosome separation during mitosis and maintaining cell shape apart from some cellular transport within the cell.

1. Distinguish between the cell theory and organismal theory.

The cell theory - living organisms are made up of cells that are individual and have specialized functions. The activities of the organism as a whole is the total activities carried out by the individual cells. The organismal theory - the plants or animals are not made up of single units of cells, but instead are made up of continuous mass of protoplasm that over the course of time have divided to form cells. The cell theory - cells more important than the entire organism as a whole. The organismal theory - entire organism of prime importance rather than the cells. The cell theory - applicable to both plants and animals in general The organismal theory - particularly applicable to plants as they have plasmodesmata, which connect the cytoplasm of the cells. Thus even divisions of cells in plants, the cells remains interconnected by means of plasmodesmata and thus are never completely separated.

4. What are the main parts of a mature eudicot or monocot embryo?

The embryo of eudicot or dicot plant consists of embryo axis (tigellum) and two cotyledons. The embryo axis consists of two ends- the radical and the plumule. The cotyledons are attached to the embryo axis at the region, which represents the first node of embryo. The part of embryo axis between radicle and first node is called hypocotyl while the part between plumule and cotyledons is called epicotyl. The monocot embryo consisting of a single shield shaped cotyledon (scutellum) and axis. The upper portion of the axis is the plumule which is covered by protective sheath called coleoptile and the lower portion is the radicle which is surrounded by another sheath called coleorhizae.

5. How do primary cell walls differ from secondary cell walls?

The main points of difference between the primary cell wall and the secondary cell wall are: Primary cell wall is composed of cellulose, hemicellulose, proteins, water, enzymes, and pectins. They may also contain lignin, suberin, or cutin. Secondary cell walls are primarily composed of cellulose hemicelluloses. Cells of wood that have secondary cell walls also contain lignin as one of the major components. Proteins, enzymes and pectins are ABSENT in secondary cell wall. - The primary cell wall is deposited before the plant cell is formed and during the growth of the plant cell. The secondary cell wall is formed after the plant cell has stopped growing and usually the cell dies in sometime after the formation of the secondary cell wall. Primary cell walls are capable of division and forming new cells thus they are responsible in wound healing and regeneration of the plant. Secondary cell wall are not capable of division and thus their main function is in strengthening the stems or other parts of the plant and in conduction of water.

How does the cortical array of microtubules contribute to cell wall synthesis?

The mitotic spindle helps chromosome movement in mitosis. The PPB (Pre-Prophase Band) predicts plane of cytokinesis. The Phragmoplast is responsible for cytokinesis. The Interphase Array takes care of cell maintenance and wall synthesis.

8. Using the following terms, explain the process of CELL WALL GROWTH and cellulose deposition in expanding cells: cellulose microfibrils, cellulose synthase complexes (rosettes), cortical microtubules, secretory vesicles, matrix substances, plasma membrane.

The plasma membrane of plants has rosettes. Rosettes complexes are movable complexes and they synthesize the new cellulose microfibrils. Rosettes containing the new microfibrils are added to the plasma membrane by means of secretory vesicles that fuse with the membrane. Rosettes are movable and their motility is due to the cortical microtubules that underlie the plasma membrane. the cytoplasm of the cell is increased by the secretory vesicles again, that carry matrix substances into the cell. Thus the cellulose microfibrils and rosettes help in the development of a new cell wall.

6. What is the cell cycle, and what key events occur in the G1, S, G2, and M phases of the cell cycle?

The regular repeated set of events that take place during cell division leading to the formation of new cells is called a cell cycle. The cell cycle is commonly divided into new stages: the interphase and mitosis. The interphase is further divided into three stages: G1, S, and G2 phase. G1 phase: This is the preparatory phase of the cell for cell division. In this phase, the cell doubles in size and the various organelles of the cell along with the enzymes and other molecules multiply in number. S phase: This is the synthesis phase of the cell. This is the most important phase where the DNA of the cell is duplicated and synthesized. Along with the DNA its associated proteins like histones are also synsthesized. G2 phase: In this phase, the chromosomes begin to condense and get ready for mitosis, and the other organelles like the cell wall begin to form making the cell ready for mitosis. M phase: this is the mitotic phase. In this phase, the cell undergoes mitosis with the formation of spindle fibers and the two sets of chromosomes are separated, the nucleus divides into two and finally the cytoplasm divides into two completing the cell division.

7. What is the role of mitosis? What events occur during each of the four mitotic phases?

The role of mitosis is to ensure that after cell division each cell has the same genetic material and info that the parent cell had. Thus after mitosis, the daughter cell contains a nucleus that has chromosomes complementary to the parent chromosome and also half of the cytoplasm so that cell growth and function can start immediately. Thus mitosis is necessary to maintain cellular genetic identity and function. Prophase- Chromosome Packing Metaphase - Chromosome Lining Anaphase - Sister Cromatids Pulled apart Telophase - Cells separating, wall formed

3. What developmental and functional relationships exist between the endoplasmic reticulum and the Golgi bodies of the plant cell?

The rough ER is the one that is developmentally and functionally related to the Golgi bodies. The rough ER send out secretory vesicles that fuse with the Golgi bodies. These secretory vesicles usually contain immature proteins in the form of amino acids that need to be further processed before they are sent outside the cell. Also the secretory vesicles that bud off from the trans side of the Golgi bodies use with the plasma membrane thus releasing the proteins out of the cell. The fusion of these secretory vesicles to the plasma membrane thus contributes to the growth of the plasma membrane in growing cells. the trans Golgi network also produces vesicles that fuse with tonoplast thus forming vacuoles. Since so much of secretory vesicles are pinched off from the golgi bodies, they need to be renewed. This is done by the vesicles that are released by the ER, that fuse with the forming face of the Golgi bodies, thus helping in the development of new sacs of Golgi apparatus.

Explain what is meant by the apical-basal pattern and radial pattern of the plant.

The shape of plant body mainly depends on the rate of division and growth. The primary body of organization of seedling consists of two types of patters: apical-basal pattern occurs along the body main axis of polarity and a radical pattern perpendicular to the axis. Each pattern composed of distinct morphological elements such as shoot meristems, radicle, and cotyledons elements shows the apical basal pattern, whereas the three basic tissue types such as protoderm, ground tissue, and procambium are arranged in concentric manner to give the radicle pattern.

What are some of the ways in which the shoot emerges from the seed during germination? What is meant by epigeous and hypogeous germination?

The shoot emerges from the seed by the Shoot Apical Stem (SAM). The SAM cells are meristematic, which means they are capable of maintaining themselves. Some cells differentiate into leaves, stem tissue or axillary buds. Buds contain new SAMs, which can grow new branches. Chegg: Seed germination is a process in which dormant embryo of seed resumes metabolic activities and grows to produce a seedling. During germination, the seed absorbs water by imbibitions and undergoes swelling. At the time of growth, seed coat ruptures; radicle comes out through micropyle and develops into root system. The plumule comes out and develops to form the shoot system. There are two types of seed germination on the basis of behaviour of cotyledons germination-hypogeal or hypogeous and epigeal or epigeous. In hypogeal seed germination,epicotyls elongates quickly, pulling the plumule out of the soil surface. Hence, cotyledons do not come over the soil surface, but lie below it. E.g, rice, wheat, jowar, gram, ground nut etc. In epigeal germination, the hypocotyls elongates quickly, pulling cotyledons and plumule above the soil surface. E.g - castor, tamarind etc.

3. What are the three tissue systems of the plant body? Of what tissues are they composed?

The tissue systems of plant body are classified into 3 types, namely epidermal tissue system, ground tissue system, and vascular tissue system. 1) EPIDERMAL TISSUE SYSTEM: consists of epidermis and epidermal out growths. All the epidermal cells are made up of living parenchymatous cells and contain vacuolated protoplasm. Epidermis is the outer most layers covering the entire surface of the plant body. 2) GROUND TISSUE SYSTEM: also known as fundamental tissues, contains various types of tissues excluding epidermis and vascular tissues. It is formed partly from plerome and partly from periblem. Ground tissue system includes cortex, pericycle, pith, and medullary rays. 3) VASCULAR SYSTEM: Comprises the central column of both root and system axis and is called stele, which is made up of a number of vascular bundles. Each vascular bundle is made up of xylem and phloem.

3. Where might one find transfer cells in a plant? What role do they play?

Transfer cells are the ingrowths of plasma membrane. They are also present in the xylem and phloem of some plants. In some plants, transfer cells are associated with companion cells of phloem. These are the specialized parenchyma cells that allowing the increased surface area for transfer of solutes etc. They facilitate the translocation of sugars from source to sink. They also helps in absorption or secretion of nutrients. they are found in the various tissues of reproductive tissues such as embryo sac, endosperm, placenta etc. In some carnivorous plants these cells are seen in glandular structures like nectaries, glands etc.

True/False "Microtubules are assembled from protein dimers. MTs can be polymerized and depolymerized many times.

True

True/False Actin and myosin are responsible for muscle contraction in animal cells and cytoplasmic streaming in plant cells.

True

The organelle that regulates turgor pressure is a/an _______ ??

Vacuole

5. What are the principal conducting cells in the xylem? In the phloem? Describe the characteristics of each cell type.

XYLEM - is the chief water conducting tissue of plants. The xylem tissue is made up of four constituents namely tracheids, vassels (tracheary elemnts), fibers, and parenchyma. Out of which, tracheids and vessels or tracheary elements are the main conducting channels of vascular plants. Besides they are mechanical in function. Tracheids are the elongated, tubular cells with tapering ends and are dead at maturity. The cell wall is thick due to deposition of lignin. The trachieds possess various kinds of thickenings. The vessels are also elongated tube like structures. The walls of vessels are lignified, relatively less thick and the cell cavity is wider. They show different patters of thickenings like tracheids. PHLOEM - transports organic food inside the plant body. It is made up of sieve cells of sieve tube elements, companion cells, phloem parenchyma, and fibers. Out of which, sieve tube elements are the main conducting channels of phloem. These are elongated and tubular structures. Sieve tube is a living cell with a layer of cytoplasm, but without nucleus.

6. Describe the cell types that occur in the epidermis and the roles they play.

epidermal tissue system or integumentary tissue system consists of epidermis and epidermal out growths. Epidermis is the superficial layer covering the entire surface of the primary plant body. The epidermis covered with cutin layer is called cuticle. Epidermis of root is called epiblema or rhizodermis. The epidermis of aerial parts usually bears a number of minute pores called stomata, which area used for transpiration. In some monocot leaves, epidermis contains some enlarged cells, which are called bulliform cells and responsible for rolling leaves. Trichomes and emergences are the epidermal out growths. They prevent excessive transpiration. The velamen of aerial roots is also spidermal in origin and is used for gaseous exchange.