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1、Physiology of Plant Growth1 Seed GerminationnFactors influencing seed germination:Water, O2, Temp., LightnWaternsoften the seed coat, radicle elongates easily.n O2 permeability, embryo metabolism rises.ngel to sol activates enzymes.nstored macromolecular substance hydrolysisnPlant hormone from the c
2、onjugate to free form.n30-70% water content for starchy seed germination and more than 110% for protein seed (soybean) germination.(2) TemperatureqThree cardinal points: “minimum, optimum and maximum”qOptimum temperature of germination is the temperature at which seeds germinate fastest with highest
3、 germination rate.qThe larger difference (10) between day and night favors to germination.qThe sowing should be conducted at the temperature 2-3 above the minimum temperature in production.(3) O2qSufficient O2active metabolismgrowth fast germination.q Deficient O2anaerobic respirationover exhausting
4、 stored substance and alcohol toxification.q Oil seeds (soybean, peanut, sun flower require more O2 than starchy seeds (wheat, corn), RQ4%) to phloem. Middle (2.5-3.5%) to both and the concentration can induce cambium. (3) Light：poor differentiation without light.(4) Polarity : The tissues and organ
5、s 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 Tissue CulturenPlant Tissue Culture, also called mic
6、ropropagation, is a practice used to propagate plants under sterile conditions, often to produce clones of a plant .nThe theory basis for plant tissue culture isTotipotency: All differentiated plant cells retain all the genetic information required for the development of a complete plant. (exception
7、: dead cell or cell without nucleus)Advantages using tissue culture over traditional propagationnThe production of exact copies of plants that produce particularly good flowers, fruits, or have other desirable traits. nTo quickly produce mature plants. nThe production of multiples of plants in the a
8、bsence of seeds or necessary pollinators to produce seeds. nThe regeneration of whole plants from plant cells that have been genetically modified. nThe production of plants from seeds that otherwise have very low chances of germinating and growing, i.e.: orchids and nepenthes. nTo clean particular p
9、lant of viral and other infections and to quickly multiply these plants as cleaned stock for horticulture and agriculture Other ApplicationsnMicropropagation can be used to produce large numbers of identical individuals. nMicropropagation can also be used to conserve rare or endangered plant species
10、. nA plant breeder may use tissue culture to screen cells rather than plants for advantageous characters, e.g herbicide resistance/tolerance. nLarge-scale growth of plant cells in liquid culture inside bioreactors as a source of secondary products, like recombinant proteins used as biopharmaceutical
11、s. nTo cross distantly related species by protoplast fusion and regeneration of the novel hybrid. nTo cross-pollinate distantly related species and then tissue culture the resulting embryo which would otherwise normally die (Embryo Rescue). 1) Culture mediumn5 groups of ingredientsqMinerals such as
12、N P S K Ca Mg Fe Mo Zn Cu BqCarbon source: usually sugar of 2-4%qVitamins: thiamin, niacin, inositole,VB6qOrganic addictives: such as coconut milk, yeast power.qPlant growth regulators: such as 2,4-D, NAA, KT, BAnCulture medium can be made as fluid or solid by adding argar of 0.6-0.7%.nCulture mediu
13、m should be sterilized by a autoclave.nThe optimum temp is about 23-28nThe optimum light intensity is 30010000Lux, generally 1000lux is enough.2) Explant nThe tissue which is obtained from the plant to culture is called an explant.nTheoretically, a totipotent explant can be grown from any part of th
14、e 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 plants1. Callus pathway (organ regeneration pathway) explantcallusnew plantAdventitious roots adventitious budAdventitious
15、 bud adventitious rootAdventitious 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 dedifferentiated cells differentiate to specialized
16、forms. n2. Embryoid pathway: qDevelop 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”.nCluster seedling pathway:qUse buds as explant3 Plant growthnGrand period of plant growthnThe growth of tissues, organs and even a whole plant exhibit a t
