Ch 9 BIO HL

Plant growth

Indeterminate (never stops_/

Auxins also involved in:

Stimulation of cell diviison in most meristematic tissue diffentiation of xylem and phloem development of lateral roots in tissue cultures suppression of lateral bud growth when present in the apical bud stimullation of growth of flower oats induction of fruit production wihtout pollination

Meristematic tissue

all tissue in plant derived fom this. Composed of aggregates of small cells that have the same function as stem cells in animals. When they divide, one remains meristematic and tje other is free to differntiate adn become part of teh plant body. Cells tha tremain meristematic are referred to as intials, while he cells that begin diffentiation are called derivatives.

plant exudat

any fluid that moves out of the normal transport system of plants.

Tissue in plants

dermal tissue - outer covering that protects against physical agens and pathogenic organisms, prevens water loss, and may have specialized structures for various pruposes - ground tissue - consists of mostly thin-walled cells that function in storage, photosynthesis, support, and seretion - vascular tissue - made up of xylem and phloem that cary out long-distance conduciton of water, minerals, and nutrients within the plant, and provide support. derived from meristematic tissue.

Trasnpiration

loss of water as gas from leaves, The water lost is important in cooling leaves and stems. More than 90% if teh water taken in by rots is lot this way

Sequence of events in the stem cuaing it to bend towards light source

1 Auxin produced by al cels in the stem on the side towards the light source 2. auxin moves by efflux pump action into the nuclei of cells on the side of the stem oppostire the light 3. the auxin and a receptor in the nuclei form a complaex that activates a proton (hyrdogen ion) pump. Auxin itsef=has an effect on teh protein pump of the stem cel membranes. 4. The proton pump moves hydrigen ions into the spaces of the cell wall 5. tese hydrogen ions cause a drop in pH< resulting in the hydrogen bonds between celllulose fibres and teh cell wall breaking 6. this results in the elongaton of cells on teh side away from the light.

Angiosperms

ANy plant that has a flower. MOst fkowering plants coevolved with pollinator species, such as insects, bats, and birds. Facillitate transfer of male pollen to the female reproductive portions of flowers so that fertilization and seed development withn the ovaries can occur. Angiosperms grouped into two classe based on morphologial characteristics. : Monocots: parallel venation (the system of veins) in leaves; three flower parts, or multiples of three; seeds contain only one cotyledon (seed leaf); vascular bundles arranged throughout the stem; root system mainly fibrous; pollen garin wiht one opening, Dicots: netlike venation pattern in leaves; four or five flower parts, or multiples of four or five, seeds contain two cotyledons (seed leaves); vascular bundles arranged as a rings in teh stem; root system incolves a taproot (main root); pollen grain with three openings. Mew grouping has occurred based on phylogeny (evolutionary history) of angio sperms. THey are, teh magnoliid complex (magnolias and laurels), the monocots, and eudicots (true dicots).

Pollination and Fertilization

All plants how two difernt generation in their life cycels: Gametophyte generation - haploid Sporophyte generation - diploid In plants, these two generation alternate with one another (alteration of generations). The gametophyte generation produces the plant gametes by mitosis, wheras teh sporophyte generation produces spores by meiosis. Flowering plants in sporophyte generation. It grew from a zygote and produces new cells by mitosis. When cherry tree produces flowers, haploid spores are formed and develop into the haploid bodies known as gametophytes. Spem form within the male gametophytes, and eggs form withing the female gametophytes.

Lateral Meristems

Allow the growth in thickness og plant. Secondary growth. Most tress and shrubs have active lateral mersitems. Most have two types; Vascular cambium - produces secondary vascular tissue and lies between the xylem and the phloem in teh vascular bundles, on the inside it produces secondary xylem, which is a moajor compenet of wood, and on teh outside it produces secpndar phloem. cork cambium - occurs within the bark of a plant and produces teh cork cels of teh outer bark.

Types of flowers

Complete flowers - contgain all four basic flower parts, the sepals, petals, stamen, and carpe INcomplete flowers - lack at leadt one of the four basic parts Staminate flowers - only have stamen and no carpels Carpellate flower - only have carpel, no stamen.

Environmental effects on transpiration in most plants

Light - speeds up transpiration by warming the leaf and opening stomata Humidity - decreasing humidity increases transpiration b/c of the greater difference in water concentration wind - increases teh rate of transpiration becuase humid air near the stomata is carried away temperature - increasing temperature causes greaer rtanspiration because more water evaporates soil water - if the intake of water at the roots does not keep up with trasnpiration, turgor loss occurs and the stomata close, adn the transpiration rate decreases. Carbon dioxide - High CO2 levels in the air around the plant usually cause the guard cells to lose turgor and teh stomata to close.

The control of flowing in angiosperms

Light very importat. required for photosynthesis, and control many aspects o fplant growth and development. Plants are able to detect teh presence of light, its direction, wavelenth, and even intensity. Photoperiodism is the plant's response to lightinvolving the relative lengths of day and night: a very imortant factor incontrolling flowerinf. Long-day plnat - flowers when days are longest and nights are shortest (midsummer) - radishes, spinach and lettuc Short-day plants - flowers in spring, late summer, and autumn, when days are shorter - poinsettas, chrysanthemums, and asters Day-neutral plants - flower without regard to day length - roses, dandelions, and tomoateos. though name refers to day, it is actaully length of night that ontrols the flowering process in plants.

The seed

Means by which an embryo can be dispersed to distant locations. It is a protective structure for the embryo. Seeds of dicotyledonous plants usually contain these parts. Seed parts: Testa - a tough, protective outer coat Cotyledons - seed leaves that function as nutrietn storage structures Micropyle - a scar at teh opening when the pollen tube enterd the ovule Embryo root and embryo shoot - become the new plant when germination occurs. Once seeds are formed, a maturation process follows. This process involves dehydration until teh water content of the seed is about 10-15% of its weiht. At this point, the seed usually goes into a dormancy period. This is a time of very low metabolism and no growth or development. The domrancy period is variable for diffent seeds. This represents an adaptation feature to overcome harsh environmental conditions. If conditions favoribel, the seed will germinate. Germination is the development of the seed into a fucntional plant. Serval genral conditions that mst be present: water is nedded, to rehydrate the dried seed tissue; oxygen is needed, to allow aerobic respiration to produce ATP; an appropriate temerature for the seed is necessary (important for enzyme action). Other conditions for some: in some seeds the testa must be disrupted or sacrificed (broken" before water uptake can occur. other seeds must be exposed to fire or smoke before tehy germinate.

Apical Meristems

Mersitems are often differntiated based on tehir ocation within the plant. Apical meristematic tissue, primary meristme, occurs at the tips of roots and stem. The apical meristem and surrouding developing ittsue are know as teh shoot apex. The shoot apex produces new tissue and cuase primary grwoth througgh the process of mitosis and celldiciosn. Primeray grwoth allows the root to extend throughout the soil it aslo allows the stem to groow longer and so increases exposre to liht and CO2. This type of growth results in herbaceuous, non-woods stems and roots.

Mineral Ions

Mineral ions must move into root. there are thrre major process that allow mineral item to pass from the soil to the root: 1. Diffusion of mineral ions and mass flow of water in that carries these ions (bulk flow or mass flow) 2- teh action of fungal hyphae - symbiotic relationship hyphae form a cover over the surface of young roots. Cretates a larger surface area for water and mineral ion absorption. Mycorrhizae 3. active transport - proton pump may be used to transport mineral ions and solutes such as potassium inos, nitrogen-based ions, and even simple sugats. Form of chemiosmosis - ATP is broken down to alow various mineral ions to move into the root cells.

Cohesion-tension theory

Process ---> Explanation water moves down concentration gradient ---?> the spaces wihtin a leaf have high concentration of water vapor. WAter moves from this location to teh atmosphere, which has a lower water concentration. Water lost by transpiration is replaced by water from the vessels ---> replacing water from teh vessel maintains a high water vapor concentration in teh air spaces of the leaf (within spongy mesophyll). The vessel water colum is maintained by cohesion and adhesion ---> cohesion involves the hydrogen bonds that form between water molecules. Adhesion involves the hydrogen bonds that form between wtaer molecules and the sides of essels; adhseion counteracts gravity. Tension occurs in the colums of water in teh xylem ---> this is becasue of water loss in the leaves adn teh repacement if that lost water by xylem water. The water columns remain continuous becasue of cohesion and adhesion. Water is pulled from the root cortex into the xylem cells ---> cohesion and adhesion maintain the columns under teh tension created by transpiration Water is pulled from the soil into the roots ---> this happens becasue of the tension created by transpiartion adn teh maintenance of a continuous colum of water.

Pollination

Process by whihc pollen (containing male sex cells) is placed on the female stigma. Pollen can be crried from anther to stigma by a varety of means. The earliest seed plan relid upon wind as theri polen vector. Later, insects. Other vecotrd include birds, water, and animals. Most flowering pants use mutualistic relationshps with pollinators in sexual reproduciton. Flowers of plants that involve insect or other pollinator emply various menas to attract theri vector. EX: red flowers are conspicious to birds; yellow and orane are noticed by bees; heavily scented flowers can be located at night. Plants that rely on wind as their pollen vector have inconscpicious, odorless, flower parts. Two general types of pollination: - self-pollination - pollen from anther of the smae plant fulls upon its own stigma. Form of inbreeding and produces less genetic varioation wihtin a sepcies. Cross-pollination - pollen is carried fomr the anther of one plant to the stigma of a differnt plant in the same species. INcrease variation adn may result ni offspring with better fitness. The probelm is that the femae stigma may not receive the male pollen becuase f longer distance to travel.

Roots and fluid movement in plants

Roots provide mineral ions and water uptake for the plant. Have extensive branching pattern and specialized epidermal structures called root hairs, which increased teh surface area over which water and mineral ion can be absorbed by a facotr o nearly 3. The root cap is important in protecting the apical meristem during primary growth of the root through the soil. The three root zones indicate regions of cell development: -The zone of cell division is where undifferentiated cells are forming, corresponding with the < phase of the cell cycle. - teh zon eof elongation is where cells are enlarging in size, corresponding with the G1 phase of teh cell cycle - The zone of maturation is where cells become a fuctional part of the plant. Water moves into the root hairs from the soil becuase the root hairs have a higher solute concentration and a lower water concentration. Comes in by osmosis, then moves to the vascular cylinder which contains teh xylem and phloem. Epidermis-cortex-endodermis-pericycle-pjhloem-xylem

Flower part ---> Function

Sepals -protect the flower while it is inside the bud Petals - often colorful to attract pollinators Anther - part of teh stamen that produces the male sex cells (pollen) Filament - stalk of the stamen that holds up the anther Stigma - sticky top of the carpel, on which pollen lands Style - structure of the carpel that supports teh stigma Ovary - base of the carpel, in which female sex cells deveopl Entire female part of the flower is called the carpel. Term pistil is used to reger to a single carpel or a group of fused carpels. Theentire male part iof teh flower is called teh stamen

Plant hormones

Specifc cells have proteins (receptos) in tehir plasma membrane, cytoplasm, or nucleus that allow them to receiev different environmental stimuli. Upon receiving certain stimuli, the protein receptor become activated, initiiating a metabolic pathway. This pathway often results in the production of a hormone (chemcial messenger) THese hormones are produced in ery smal amount and have effects in many parts of the plant. Move in plant throgh the phlowm or from cell to cell. Target cell are targets of hormone. Differ than animal hormones. PLant hormones have varying effects depending on teh receptor locaation in teh plant. In plant, unlike in animals, there is often a great deal of communication betwen teh different hormones to bring about teh most appropriate response. IN animals, it is common for one specialized gland or cell to produce a hormone. In plants, a hormone may be produced throughout the platn.

Phytochrome

The control by light is brought about by sepcial-blue green pigmens in the plants (phytochromes). One form is inactive is represented by P(r). THe other is active and is repersented by P(fr). When red light (wavelength 66nm) is present in availbale light, the incative form of phytochrome, P(r), is ocnverted to the active form, P(fr). Thsi conversion occurs rapidly. P(fr) has teh ability to absorb far-red light (which has a wavelngth of 730 nm). This P(fr) is rapidly converted back to Pr in daylight. However, in darkness the conversion back to Pr is very slow. It is though that this slow conversion of Pfr back to Pr is what allows the plant t otim the dark period. This seems to be controlling factor for flowering in short-day and long-day lplants. In long day plants, teh remaining Pfr at teh end of a short nigght stimulates the platn to flower (promoter). In short-day plants teh Pfr apears to act as an inhibiot of flowering. In short-day plants, enough Pfr has to beconverted to Pf for flowering to occur. Pfr is able to stimulate flowering by activation specific genes of teh shoot apex cells on a plant, caysing changes in DNA trancription.

Auxins and phototropism`

Troposims are generally defined sa growth or moevement to directional external stimili. They may be postve (toward the stimulus) or negaitve (away). Common stimuli include checmials, gravity, touch, and light. Generally plant stems exhinit positive phototropism, adn plant roots demonstrate negative phototropism. If area crowded, it is essential foreedlings o gro toards he sunlight. Auxins are hormones that case teh positve phototropism of plant shoots and seedlins. Auxins are found in teh embryo of seeds, the meristems of apical buds (shoot apex), and young leaves. Only works on plant cells that have auxin receptis. Auxins appear to increase teh flecibitlity of plant cell walls in young developing shoots. THis enables elongation on teh side of the shoot necessary to casue growth towards the light. The growth response does not appear to be the result of an increased production of auxin ion one side of teh shot. Rather, it seems to caused by a redistribtuoin of available auxin, especually to the side of teh stem away from the light source. IN teh case of phototropism, auxin is actually produced in all cells in this region of the pant. Auxin effluc pumps (Specialized membrane proteins) move the auxins out of the cells closer to lught, using ATP as the neergy souce. This pmping action creates a high conecntration gradient of auxin in the space between cells. This results in a greater concenration of auxin in teh intercelluluar space and a low conecntration within adjacent cells. Because of this, auxin moves down the concentration gradies=nt forom teh intercellular space into the adjacent cells. Then entry of auxin into the cell is alled AUXIN INFLUX> Rhe mechanisms of auxin movement between adjavcent cells continues unitl their is a greater concentration of auxin on the stem's dark side. The result is a great elongation of cells on teh stem side away from teh light and, therefore, curvature towards teh light souce. The specifci platn auuxin inloved in this action is indoleacetic acid (IAA). Elongation occurs when auxin combines with a receptor that target specific transriction repressors of auxin-responsive genes.

Basic leaf struucture

Water is lost in the form of a gas from the leaf through opening called stomata (stoma sing.). Transpiration is the term given to the loss of water vapor from leaves an otehr aerial parts of the plant. Th water lost must be replacde by water absorption. Leaves - flattened poriton called the blade and a stalk called teh petiole that attaches the blade to the ste,. Cuticle - waxy outermost layer, protects against water loss and insect invasion. If cuticle not present, outrmost layer is epidermis that protects the plant. Leave have vascualr tissue caled xylem and phloem. The xylem brings water to the leaves, while the phloem carries the products of photosynthesis to teh rest of the platn. Occur together in veins or vascualr bundles Palisade mesophyll - densley packed region of cylindrical cells in the uppe rportion of the leaves. Contain large numbers of chloroplasts to carry out photosynthesis. Spngy mesophyll - bottom portion of the leaves. Loosly packed cells with few chloroplasts. Many air spaces, which provide gas exchanhe surfaces. Stomata - bottom surface of leaves, and ey allwo O2 and CO2 exchange b/w the leaf and surrounding environemnt. AS the're exhanged, water is lost. Specialized cells called guard cells control the opening and closing of the stomata. - palisade mesophyll - upper poriton of el

Fertilization

When male and female sex cells unite to form a diploid zygote. The female sex cells are present withn the ovules of teh flower. The ovules are within the ovary of the carpel When the polen grain adheres to the stigma (covered in sticky sugary substance) it begins to grow a pollen tube. Pollen tube growth and fertilization occur in the following sequence: -pollen germinates to produce a pollen tube - the pollen tube grows down teh style of teh carpel - within the growing pollen tube is the nucleus that will produce teh sperm - the pollen tube completes its growth by entering an opening at the botton of the ovary - the sperm moves from teh tube to combine with the egg of the ovule to form a zygote. -once the zygote is formed it develops with the surrounding tissue into teh seed. AS teh seed is developing, the ovary around the ovule matures into a fruit. The fruit encloses, and helps to protect, the seed. Fertilization is actually double fertilization. After pollination, one of the two sperms produced by the pollen grain combines with the egg. The other combines wiht two polar nuclei within the ovary to produce a triplod (3n) endosperm. The endosperm has the funciton of storing nutrietns for the young plant.

lignin

compex organic compound that greatly strengthe\ns the cell walls of vascular plants. Waterproofs plant parts and adds protection against pathogens. Pirmary cell wall made up of cellulose. IN some plants, as teh cells age they forom a secondary cell wall composed of oher materials. One of theess i ilgnin. Transpiration0cohesion-tension mechanisms (cohesion-tension throy) movement of mineral and water upwards in plants.

Stomata and guard cells

guard cells irregulary shaped, with cell wall thickness being greater near teh stoma. The stomata open and close based on turgor pressure of the guard cells. When teh cells take in water and swell, they buldge more to teh outside, opening the stoma. When teh guard cells lose water, they sag towards each other and close the stoma. The gain and loss of water cells il largely because of teh transport of potassium ions. Light from teh bue part of light spectrum triggers teh activty of adenosine triphosphate (ATP)=powerd proton pumps in teh plasma membrane of guard cells. ths triggers active transport of potassium into teh cell. The high solute concentration within teh guard cell causes inward movement of water by osmosis. When potassiom ions leave the cells, water also leaves. The pat hormone abscisic acid causes potassium ions to diffuse rapidly out of the guard cells. Horomone produced during timesof water deficiency.

phloem

organic moleculs transported. made up of sieve rube members and their companion cells. Sieve tube members are connected to one anotehr by sieve plates to form sieve tubes. Sieve tube are refered to as sieve elements. The sieve plates have pores that allow teh movement of wate and disolved organic molecules throughout the plant. Companion cells are connecte to their sieve tube members by plasmodesmata. Xylem only goes up. phloem transports in various directions. Movement is based on a single principle: ot's fom ra source to a sink. A source is a plnat organ that is a net producer of suger, either by photosynthesis or by teh hydrolysis of starch. Leaves are the promary sugar sources. A sink is a plant rgan tha uses or stores sugar. Roots, buds, stem, seeds, and fruits are all sugar sinks. Some can be both source and sink EX: a tuber or bulb may be storing sugar or breaking down starch to provide sugar, depending on the season: tubers and bullbs act as sins inte summer and as sources in teh early spring. Translocation - movement of organic moelcules in plants. They are dissolved in water and teh solution is referred to as phloem sap, which includes: sugars, amino acids, pant hormones, small RNA molecules.

Pressure-flow hypothesis

phloem sap can move as fast as 1 mper huor. Radioactive tracers can study this movement, and show that more than just diffusion and osmosis are involved. STEPS: 1 - loading of sugar into the sieve tube at the source. This reduces the relative water concentration in teh sieve tube members, casing osmosis from teh surrounding cells. 2 - the uptake of water at the source causes a positive pressure, called hydrstatic pressire, in the sieve tube, which results in a flow (bulk flow) of the phloem sap. 3 - the hydrstatic pressure is diminshed by the removal of sugar from teh sieve ube at the sink. The sugars are changed at the sink to starch. Starch is insoluble and everts no osmotic efect 6 - xylem recycles the relatievy pure water bu carrying it fromthe sink back to the source. The loading of sugar into teh sieve tube at teh source, adn teh removal of sugar at the sink is accomplished by active transport. Chemiosmotic prcoess involving proton ums and spealized membrane proteins called cotranport proteins that allow both passive and active transport. the companion cells of the phloem are incolved with the active tranpsort process. Movement through phloem is a passive transport becasue hydrostatoc pressure grasients, whcih is produced by the compression of a liquid in confined space or by the additionof solute particles toa liquid ina confined area. Sieve tubes are hollow, conductve cells without a nucleus. ATP provided by companion cells, whcih occur adjacent to sieve tubes. COmpanion cells have nuclei and are also responsible for keeping teh siev tubes members alive.

Xerophytes

plants adapted to arid environment. Adaptions to reduce transpiration water loss- -small thick leaves reduce water loss by decreasing the surface area of the leaves - a reduced number of stomata - stomata are located in crypts or pits on the eaf surface. Causes higher humidity near teh stomata. -a thickened waxy cuticle reduces water loss bby acting as an impenetrable barrier to water - hair like cells on teh leaf surface trap a layer of water vapor, maintaining a high humidity - shed leaves and/or become dormant in the direst moneths. - cacti exist on water that the plant stores in fleshy, watery stems. Plants like this called succulents. - xerophytescan used alterantive photosynthetic processes. regular photsynthesis (C3 photosynthesetic pathway). Two other types: CAM plants close stomata during the day and incorpoate CO2 during the night. C4 plants have stomata open during the day but take in CO2 more rapidly than non-specialized plants.

Halophytes

plants adapted to grow in water with high levels o salinity. Promising source of biofeul becasue they do not compete with food crops for resources. Adpatations- -many become succulent by storing water, thus diluting the salt concentrations - can secrete salt thruogh salt gands - can compartmetnalize NA and CL in teh vacuales of their cells, therby prevnting NaCL toxicity - sunken stomata on thicklened leaved reduce water loss by creating a igh humidity ear the stomata. thickened leaves also have more dveloped cuticle to minimize water loss. - surface ares of leaves reduced.

xylem

support and transport water due to water-conducting tissue. Composed of many cell types. The two involed in water transport are tracheids and vessel element. Tracheids are dead cells that tapes at teh ends and conect to one another to from a continuous column. Vessel elements are aldo dead cell, and have a thick, lignified secondary wall. These secondary walls ae often interrupted by areas of primary wall. These prmiary wall areas also include pits or pores that allow water to move laterally. The vessel elemnts are attached end to end to form columns, like the tracheids. The ends of the vessel elemtns have perforations (pores) in tem, allowing water to move freely up the plant.