PLANT DEVELOPMENT & REPRODUCTION - CBSE International

More documents

Recommendations

Info

Commercial Application of GA1. GAs Promote the growth of fruit crops and increases the sugar yield in sugarcane.2. Inhibitor of GA (cycocel) is also used commercially, where the reduction in plant height isrequired to remove the problem of hedging.Activity 2Aim: Comparison of the inter-nodal growth by application of Gibberellin.Material required: dwarf and normal seedling of locally available plants, GA solution (0.1 mM),water, containerProcedure:1. Take ten days old seedlings of dwarf and normally growing, locally available plants.2. Divide them into the two groups.3. Each of the groups is treated with Giberellin-solution (0.1 mM) and a control-solution(containing no hormone) and kept for fifteen days.4. The inter-nodal distance was taken initially and at the end of experiment.Result and discussion: After observation each result should be recorded in tabulated form anddiscussion should be based on that data. The result would be visible as increase in height in dwarfplant in comparison to control. The result can be expressed as percent change from control. Thediscussion can be centred around the physiological mechanism.Q.1. What is bolting, explain with the help of above example.Q.2. Do you see any application of above activity, give some examples.CytokininIt is cell division inducer and senescence delaying hormone.It is third group of plant growth promoting substances. Cytokinin has the ability to inducecell division in culture or natural tissue system. After knowing the secret that plant cells aretotipotent, tissue culture experiments grew rapidly. But scientists were desperate to find suchsubstance which can induce the division in cultured tissue. In this search race, F. Skoog andC.O. Miller in 1940 and 1950 (University of Wisconsin), after testing many substances, foundthat aged or autoclaved DNA had amazing cell division promoting effects. This small moleculewas identified as adenine derivative, 6-furfurylaminopurine and named as kinetin. Thoughkinetin was not naturally occurring plant growth hormone but its importance led to vigorousresearch to search such substance from plant and plant origin. This effort brought the discoveryof first natural cytokinin from immature endosperm of Zea mays. Letham (1973) isolated andidentified it as trans-6 (4-hydroxy -3-methyl but-2-emyl amine) purine and named as Zeatin.Zeatin had molecular structure similar to kinetin. Further discovery yielded more cytokinin fromplant origin such as riboside, ribotide or glycoside. Along with naturally occurring cytokine,some synthetic compounds like Benzyl adenine (BA), Thidiazuron also behaves as cytokinin.BA is popularly used as a defoliant and herbicide.Cytokinin is aminopurine containing side carbon chain. Major source of synthesis of freeUnit 1 Plant Development & Reproduction 14
cytokinin is root apical meristem. Cytokinin moves from here to shoot through xylem. Cytokininis synthesized in root tip, phloem, leaf axils, cambial tissue, developing ovule and seeds.Cytokinin level, in plants, is regulated by negative feedback and auxin level. Cytokinin oxidaseenzyme metabolizes cytokinin into adenine and 3-methyl-2-butenal and limits the cytokininactively. Sometime cytokinin is stored in inactive form by making conjugate with glucose ascytokinin glucosides.Biological role of cytokinin: It regulates cell division in shoot and root. This regulation controlsthe specific component of the cell cycle that is performed by interaction of cytokinin with cellcycle regulator protein known as cyclin dependant kinase (CDK) that results in cell divisions.Auxin and cytokinin ratio regulates morphogenesis in cultured tissue. High auxin cytokininratio results in root development and low auxin cytokinin ratio develops Shoot part. Cytokininantagonizes the effect of auxin of apical dominance by promoting lateral bud growth. Cytokinindelays senescence by preventing the degradation of chlorophyll and proteins. This has beentermed as the Richmond-Lang effect. Cytokinin provides movement of nutrients from otherparts to leaves.Activity 3Aim: To study the hormonal crosstalk in plant system considering cytokinin and auxin, and evaluatethe effect by observing the effect as single and in combination, on growth and differentiation ofplant tissue in vitro.Material required: Locally available small herbaceous plant (such as tomato, tobacco), basicculture medium containing cytokinin and auxin for growth of plant, culture tube, ethanol forsterilization, razorProcedure:1. The root, top shoot and leaves are discarded from the top of plant (~50 cm) includingapex region and middle stem is kept for experiment.2. Remove the bark or dead skin and carefully sterilize the cut portion by 70% ethanol.3. Cut the stem transversely into small pieces and pith portion is obtained by the use of thincork borer.4. These pith portions are transferred to culture tubes containing various combinations ofhormones with culture medium.5. Examine the cultures at regular intervals and these are to be supplied with all therequirements for growth.6. Precaution is taken to maintain the sterilized condition to avoid the infection in culturemedium.Observation and result: The growth and observation were recorded in notebook until clear visiblegrowth and differentiation is seen. The tissues are also observed under microscope to analyzeit at histological level.The result should be discussed and several questions must be asked pertaining to combinationeffect, single or absence of hormone. There should also be a discussion on the failure ofexperiment to find out the causes.Q.1. How cytokinin helps in plant growth and development?Q.2. Why proper auxin and cytokinin ratio is required for plant growth and development?Q.3. What application can be made by understanding above activity?Unit 1 Plant Development & Reproduction 15
Page 3: The CBSE-International is grateful
Page 6 and 7: PrefaceEducation plays the most imp
Page 8 and 9: AcknowledgementsAdvisoryShri Vineet
Page 10 and 11: 2. Cell enlargement: In this phase,
Page 12 and 13: Auxanometer(Gr. auxain, “to grow
Page 14 and 15: with simple cell/organism like bact
Page 16 and 17: Primary and Secondary growthin a tw
Page 18 and 19: activity, such as Indol-3-ethanol,
Page 20 and 21: Commercial use of AuxinUse of auxin
Page 24 and 25: ABA (Abscisic Acid) Savoir from adv
Page 26 and 27: OHEthylene is also involved in the
Page 28: Salicylic acidIt is naturally occur
Page 31 and 32: carried out mainly by two types of
Page 33 and 34: conditions are favorable and ample
Page 35 and 36: Figure 23: Flower showing the male
Page 37 and 38: What would be theploidy of the cell
Page 39 and 40: Activity 6Aim: To study the pollen
Page 41 and 42: Megasporogenesis: The process of fo
Page 43 and 44: synchronized. Either the pollen is
Page 45 and 46: Pollination by water is quite rare
Page 47 and 48: on the stigma. The pistil has the a
Page 49 and 50: Antipodal cellPolar nuclei(n)Female
Page 51 and 52: called coleorrhiza. The portion of
Page 54 and 55: Activity 8Observe some flowers of t
Page 56 and 57: Unlike polyembryony, the apomixis i
Page 58 and 59: of vascular plants (Dicots, gymnosp
Page 60 and 61: two polar nuclei (the second polar
Page 62 and 63: Q.4. Discuss the photoperiodism and

PLANT DEVELOPMENT & REPRODUCTION - CBSE International

Create successful ePaper yourself

Delete template?

Save as template?