1、Physiology of Plant Growth,1 Seed Germination,Factors influencing seed germination:Water, O2, Temp., Light Water soften the seed coat, radicle elongates easily.O2 permeability, embryo metabolism rises. gel to sol activates enzymes. stored macromolecular substance hydrolysis Plant hormone from the co
2、njugate to free form. 30-70% water content for starchy seed germination and more than 110% for protein seed (soybean) germination.,(2) Temperature Three cardinal points: “minimum, optimum and maximum” Optimum temperature of germination is the temperature at which seeds germinate fastest with highest
3、 germination rate. The larger difference (10) between day and night favors to germination. The sowing should be conducted at the temperature 2-3 above the minimum temperature in production.,(3) O2 Sufficient O2active metabolismgrowthfast germination.Deficient O2anaerobic respirationover exhausting s
4、tored substance and alcohol toxification.Oil seeds (soybean, peanut, sun flower require more O2 than starchy seeds (wheat, corn), RQ1 。Shallow-sowing in practice.,(4) Light Light seed: germination needs light controlled by red light（660nm） and far-red light (730nm). e.g. tobacco, lettuce, Arabidopsi
5、s thaliana Dark seed: germinate well under darkness. e.g. Citrullus (西瓜属) Photophobic seed：germination inhibited by light e.g. eggplant, tomato, onion,2 Biochemical changes during Germination,Water absorption: rapidslowrapid(matrix to osmotic absorption),Respiration: From anaerobic respiration to ae
6、robic respiration,Organic substances: Starch glucose Fat organic fatty acid Protein amino acids,Enzymes: From boundary enzyme free enzyme De novo synthesis Hormones: From boundary enzyme free enzyme De novo synthesis,3. Seed longevity and vitality,Seed longevity: most crops 1-3years, lotus seed:1000
7、years, pillow: 12h. Seed vitality: Seed vitality is the ability to germinate, grow and produce. It is a complicated term refers to many traits of plants.,Methods to measure seed vitality,TTC BTB Red ink Dyeing Fluorescence,BTB Gelatin,Red ink dyeing,2 plant growth and development,Development refers
8、to the sum of all of the changes that an organism goes through in the life cyclefrom germination of the seed through growth, maturation, flowering, seed formation, and senescence. Growth is an irreversible increase in size and mass. It is a quantitative term. Differentiation refers to qualitative ch
9、anges that accompany growth. It leads to morphological and functional changes of plants,Differentiation occur in various levels,Organs Tissues Cells MoleculesRoot,stem Conductive Xylem phloem genes,protein Leaf flower Absorptive Root hairs Enzymefruit MechanicAerenchymastorageEye Microscope electron
10、 microscope biochemicalmolecular biology,The Analysis of Plant Growth,Plant Growth Can Be Measured in Different Ways Fresh weight Dry weight Cell number Plant Growth Can Be Described in Both Spatial and Material Terms,1. Cell division,Factors influencing cell division Hormones: IAA GB CTK Vitamines:
11、 VB1, VB2 and Niacin stimulate cell division,2 Cell elongation,Morphology ： cell volume increase dramatically as the cell absorbs a great number of water. Combine small vacuoles into a central vacuole so that the nucleus and cytoplasm is pressed to the side toward cell wall.Water is the most importa
12、nt factor for cell elongation. GA, IAA and CTK control cell elongation,Cell elongation depends on the elongation of cell wall,Components of cell wall Cell wall is composed of : Cellulose Hemi-cellulose Pectin Structural protein Cell wall is a net work,4. Cell Differentiation,Keep volume steady and c
13、hange in morphology and function. Factor affecting differentiation.(1) Plant hormone：IAA/CTK ratio (2) Sucrose：lower (1.5-2.5%) sucrose is advantage to xylem differentiation and higher （4%) to phloem. Middle (2.5-3.5%) to both and the concentration can induce cambium. (3) Light：poor differentiation
14、without light.,(4) Polarity : The tissues and organs are arrayed in a precise order along a linear axis that extends from the shoot apical meristem (SAM) at one end to the root apical meristem (RAM) at the other. Upend gives rise to bud and basal end does root.,(5) Uneven division of cells.,5. Plant
15、 Tissue Culture,Plant Tissue Culture, also called micropropagation, is a practice used to propagate plants under sterile conditions, often to produce clones of a plant . The theory basis for plant tissue culture isTotipotency: All differentiated plant cells retain all the genetic information require
16、d for the development of a complete plant. (exception: dead cell or cell without nucleus),Advantages using tissue culture over traditional propagation,The production of exact copies of plants that produce particularly good flowers, fruits, or have other desirable traits. To quickly produce mature pl
17、ants. The production of multiples of plants in the absence of seeds or necessary pollinators to produce seeds. The regeneration of whole plants from plant cells that have been genetically modified. The production of plants from seeds that otherwise have very low chances of germinating and growing, i
18、.e.: orchids and nepenthes. To clean particular plant of viral and other infections and to quickly multiply these plants as cleaned stock for horticulture and agriculture,Other Applications,Micropropagation can be used to produce large numbers of identical individuals. Micropropagation can also be u
19、sed to conserve rare or endangered plant species. A plant breeder may use tissue culture to screen cells rather than plants for advantageous characters, e.g herbicide resistance/tolerance. Large-scale growth of plant cells in liquid culture inside bioreactors as a source of secondary products, like
20、recombinant proteins used as biopharmaceuticals. To cross distantly related species by protoplast fusion and regeneration of the novel hybrid. To cross-pollinate distantly related species and then tissue culture the resulting embryo which would otherwise normally die (Embryo Rescue).,1) Culture medi
21、um,5 groups of ingredients Minerals such as N P S K Ca Mg Fe Mo Zn Cu B Carbon source: usually sugar of 2-4% Vitamins: thiamin, niacin, inositole,VB6 Organic addictives: such as coconut milk, yeast power. Plant growth regulators: such as 2,4-D, NAA, KT, BA,Culture medium can be made as fluid or soli
22、d by adding argar of 0.6-0.7%. Culture medium should be sterilized by a autoclave. The optimum temp is about 23-28 The optimum light intensity is 30010000Lux, generally 1000lux is enough.,2) Explant,The tissue which is obtained from the plant to culture is called an explant. Theoretically, a totipot
23、ent explant can be grown from any part of the plant. However, In many species explants of various organs vary in their rates of growth and regeneration, while some do not grow at all.,Appendix: ways of getting regenerated plants,1. Callus pathway (organ regeneration pathway) explantcallusnew plant A
24、dventitious roots adventitious bud Adventitious bud adventitious root Adventitious root and bud simultaneously - Dedifferentiation is a process of regression of a specialized cell or tissue to a simpler, more embryonic, unspecialized form. Redifferentiation is a process by which a group of once dedi
25、fferentiated cells differentiate to specialized forms.,2. Embryoid pathway: Develop from a stomatic embryo to a whole plant, just like from zygotic embryo to whole plant. It also experiences “Early globular stage”, “heart stage”, “ Torpedo stage” and “Mature embryo”. Cluster seedling pathway: Use bu
26、ds as explant,3 Plant growth,Grand period of plant growth The growth of tissues, organs and even a whole plant exhibit a typical model with slower-faster slower in life cycle. The total growth appears S-shape growth curve-logistic curve.,2. Factors influencing plant growth,1) Light 2) Temp. 3) Water
27、 4) Minerals 5) others,1) Light,Indirect：by photosynthesis and transpiration. (High energy) Direct：photomorphogenesis. (Low energy) High irradiation inhibit plant gowth Blue light, UV inhibit plant growth,2) Temperature,Three cardinal points: “minimum, optimum and maximum temperature for growth” opt
28、imum temperature for growth is the temperature at which plant grows fastest but not strongest. Suboptimum temperature for growth is the temperature at which plant grows slower but strongest than at optimum temperature . Difference in temperature between day and night (thermoperiodicity) controls pla
29、nt growth.,3).Water, O2 and minerals,“Dry for root, wet for bud”. .,3. Plant growth correlation,The growth among the different organs in a whole plant coordinates and inhibits each other, which is called the plant growth correlation.,1) Root vs. Shoot,Shoot provides photoassimilate, IAA and VB1 to r
30、oots； Root provides water, mineral nutrition, plant hormones (CTK、GA, ABA) and partial AA to shoot. They must coordinate each other.,Root-shoot ratio,Root-shoot ratio is an index for the coordinative between root and shoot: Factors influencing root-shoot ratio and its regulation (1) H2O soil water c
31、ontent，the ratio. (2) Regulation with nutrition N, the ratio；N， the ratio . Leaf vegetable applied with heavy N. P and K the ratio . Tuber root applied with much P and K.(3) Sufficient light the ratio .(4) Temperature ， the ratio .Pruning， the ratio 。Tilling and breaking root，the ratio.,Main stem an
32、d Branch Apical dominance,Main stem apices grows fast and axillary bud or branch grows slowly . The reasons for dominance: (1)Nutrition hypothesis (2)IAA hypothesis-direct-inhibition model (Thamann and Skoog) , IAA inhibits branch. (3) Nutrition supply and plant hormone control theory,Vegetative Vs.
33、 Reproductive growth,The better vegetation promotes reproduction and the poorer vegetation results in poorer reproduction . Over-vegetation inhibits reproduction. Overgrowth often gives rise to late flowering, bad setting, fruit falling and yield decreasing. Over-reproduction reduces the vegetative
34、organ development and leads to plant premature.,4 Plant movement,tropical movement nastic movement Rhythm movement,1. Tropic movement,tropical movement: movement caused by unilateral stimulus. 1) phototropism,2) gravitropism,Statolith is the amyloplast in the root cap, each amyloplast is composed of
35、 1-8 starch grains. One cell containa about 4-12 amyloplasts.,2. Nastic movement,Movement under stimulus of no direction. Include: growth movement( irreversible) and turgor movement (reversible),1) Epinasty and hyponasty,Ethylene induced epinasty in tomato,2) nyctinasty,Maranta at afternoon (left) a
36、nd in the night (right),The sensitive plant (Mimosa pudica) have special structures (pulvinus) at the bases of petioles and leaflets that allow the leaf parts to close up when touched (arrow).,3) seismonasty,pulvinus,Flexor Low turgor,Extensor High turgor High K+ Cl-,Flexor High turgor High K+ Cl-,E
37、xtensor Low turgor,The role of flexor and extensor in the movement of leaves undergoing nyctinasty and seismonasty,3. Circadian rhythm,Various metabolic processes in plants, such as oxygen evolution and respiration, cycle alternately through high-activity and low-activity phases with a regular periodicity of about 24 hours.,菜豆叶在恒定条件（微弱光，20）下的运动,
