PCA PLANT GROWTH REGULATORS ACTUAL EXAM QUESTIONS AND ANSWERS.

The 'classical' five naturally occurring plant hormone groups auxins, cytokinins, ethylene, gibberellins, abscisic acid The primary physiological processes regulated by auxins cell enlargement, cell expansion, stimulates production of ethylene, promotes or delays abscission, and initiates adventitious roots The primary physiological processes regulated by cytokinins cytokinesis, tissue differentiation, budbreak, apical dominance, delays senescence, and promotes cotyledon expansion The primary physiological processes regulated by ethylene ripening of fruits, breaks dormancy, promotes abscission The primary physiological processes regulated by gibberellins cell division, cell elongation, cell enlargement, improves fruit set and enlargement, induces parthenocarpy, and plays a role in seed and bud dormancy The primary physiological processes regulated by growth retardants/inhibitors biosynthesis inhibitors, terminal bud inhibitors, ethylene synthesis inhibitors Auxins class of naturally occurring plant growth substances essential to cell differentiation, division, and enlargement IAA (3-indoleacetic acid) the most important auxin, acts as both a stimulator and inhibitor The primary uses of auxins and the crops they are used on reduces and increases fruit drop, delays maturation, blossom thinning, sets fruit, enhances adventitious root formation, delays color development. Crops:citrus, apples, olives, ornamentals, and pears The auxins contained in plant tissue IAA (3-indoleacetic acid), IAId (3-indoleacetaldehyde), IPA (3-indolepyruvic acid), IAN (3-indoleacetonitrile), IAE (Ethyl ester of indoleacetic acid) Auxin that is also used as an herbicide 2,4-D Gibberellins a family of compounds produced by plants and by a fungus species. They are important in a number of plant processes The effect of gibberellins on plant growth stimulates cell division, elongation and enlargement. improves fruit set and enlargement, induces parthenocarpy, and plays a role in seed and bud dormancy The primary uses of gibberellins cell elongation, cell division, overcoming dormancy, overcoming or breaking bud dormancy, increases or reduces fruit set, affects fruit shape, fruit maturation, delay of flowering in fruit trees, stimulates flowering and bolting in biennials, and delays senescence Compare GA3 and GA4GA7 GA4GA7 are about 5,000 times more active in stimulating elongation than GA3 The primary gibberellins used GA4GA7 and GA3 The primary crop and use of GA4GA7 Apples-increases thinning which improves fruit size, promotes lateral budbreak which increases branching on young apple trees, improves apple shape, reduces russeting Cherries-promotes lateral budbreak which increases braching on nonbearing trees The primary use of GA3 in citrus delays pre and post harvest fruit maturity, senescence, rind decay, rind coloring and over ripening which increases fruit set Cytokinins a group of naturally occurring plant growth substances and synthetic analogs that are active in stimulating cell division and delaying senescence of plant organs The effects of cytokinnins on plant growth promotes cytokinesis (cell division), tissue differentiation, budbreak, apical dominance, delays senescence, and promotes cotyledon expansion Ethylene a gaseous substance produced by all plant tissues The relationship of ethephon to ethylene ethephon is the generic term for a synthetically produced ethylene releasing compound The effects of ethylene and ethephon on plant growth promotes ripening in mature fruit, promotes flower initiation, and increases fruit size The primary uses of ethylene and ethephon on citrus fruit elimination, thinning agent, and post-harvest de-greening of fruit The primary uses of ethylene and ethephon on cotton increases lint strength, hybrid seed production, and boll opening The primary uses of ethylene and ethephon on grain crops induces fruit ripening, induces flowering, accelerates fruit and leaf abscission, promotes lateral branching, and promotes shortened stems The primary uses of ethylene and ethephon on tomato and table grapes advances ripening and accelerates pigment development or color accumulation The primary uses of ethylene and ethephon on walnuts advances hull splitting and fruit abscission The primary uses of the growth inhibitor paclobutrazol greenhouse and nursery plants-inhibits the synthesis of gibberellin resulting in reduced cell elongation and internode compression making shorter plants The primary uses of the growth inhibitor flurprimidol ornamentals-inhibits the synthesis of gibberellin resulting in reduced cell elongation and internode compression making shorter plants The primary uses of the growth inhibitor prohexadione calcium apples-reduces shoot growth and fireblight