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PLANT AND DEVELOPMENT, with cell have been identified., substances like led to the and of 'zeatin', Since then and some compounds, Kinetin does not in for natural, 327, IX-, mhey prevent fruit and leaf drop at early stages but promote the abscission of older, mature leaves and fruits, Applications/Uses, Auxins help to initiate rooting in stem cuttings, hence are used in plant propagation., nilk, They promote flowering e.g., in pineapple., Decapitation of shoot (removal of shoot tips), overcomes apical dominance and results, in the growth of lateral buds; It is practised in tea plantations and hedge making., Auxins are used to induce parthenocarpy (formation of fruits without fertilisation), e.g., in tomatoes., They are widely used as herbicides/weedicides e.g., 2, 4-D widely used to kill, dicotyledonous weeds in crop fields and to prepare weed free lawns (2.4 D does not, kill mature monocotyledonous plants)., |, wth, 1, cisic, (ii) Gibberellins, More than hundred gibberellins are reported from different organisms such as fungi, and higher plants., They are denoted as GA,, GA,, GA, and so on; All GAs are acidic., GA, is the first gibberellin to be discovered and is the most intensively studied., that, -, Physiological Effects, Gibberellins cause elongation of internodes and promote bolting (internode elongation, just prior to flowering) in rosette plants such as beet, cabbage etc., They delay senescence but hastens the maturity period, leading to early seed, production in conifers., s i.e., from, - GA, initiates synthesis of hydrolysing enzymes to mobilise the reserve food materials, in germinating seeds., They also break seed dormancy., 1) are, -, -, Applications/Uses, Gibberellins are used to increase the length of grape stalk to increase the size of, -, of the, grapes., They cause fruits like apple to elongate and improve its shape., They delay senescence, hence can be used to leave the fruits on the trees longer so as, to extend the market period., -, GA, is used to speed up malting process in brewing industry., By increasing the length of stems in sugarcane, gibberellins increase the yield of, sugarcane by about 20 tonnes per acre., -, |-, Spraying juvenile conifers with GA, hastens their maturity and leads to early seed, production., (i) Cytokinins, Cytokinins were discovered as kinetin (a modified form of adenine- a purine) from, the autoclaved herring sperm DNA., tetin does not occur naturally in plants; Therefore, the search for natural, trom corn-kernels and coconut milk.