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patterns of ageing and death plants and their parts develop continuously from germination until death the latter part of the developmental process
senescence - effects of plant growth regulators on developmentall five major growth regulator groups auxins gibberellins cytokinins abscisic acid and
aba - dormancyabscisic acid functions as an antagonist of all three promoters like iaa gas and cytokinins aba nullifies the activity of ga iaa and
ethylene - dormancyripening of fruits involves a chain of cellular events like rise in the rate of respiration breakdown of higher carbohydrates into
alpha- amylase activity by ga3 - dormancyof the enzymes required for the digestion of starch alpha-amylase appears immediately after the start of
iaa stimulates cell enlargement cell wall contains layer of cellulose fibrils and are normally quite rigid thus for a cell to grow there must be a
seed coat effects in some seeds dormancy is imposed by the presence of the seed coat if this is removed the seed germinates two possible types of
temperature - seed dormancylow temperature treatment is an essential prelude to germination in many seeds and high temperature may be inhibitory at
light requirement - seed dormancythe light requirement for germination of many seeds is presumably a mechanism that prevents the germination of small
seed dormancy - plant growth substancesseed dormancy is critically important for the survival of plants factors involved in seed dormancy area
bud dormancy - plant growth substancesenvironmental factorsthe most important factor inducing dormancy appears to be photoperiod short days induce
dormancy - plant growth substancesdormancy can be defined as a state of suspended growth and metabolism when most plants are exposed to seasonal
flower - plant growth substancesfloral initiation is a dramatic event involving a total changeover of the character and developmental pattern of the
stem - plant growth substancesthe role of auxins cytokinins ethylene and abscisic acid in controlling the apical bud dominance and lateral bud
root - plant growth substancesinduction of roots by auxins in stem cuttings is a well known phenomenon the concentrations needed are much lower as
abscisic acid aba - plant growth substancesin 1961 lice and cams isolated a substance in crystalline form from mature cotton fruit this substance
ethylene - plant growth substancesthis hydrocarbon c2h2 is a gas and is unbelievably a small and simple molecule to be accepted as a hormone ethylene
cytokinins - plant growth substancesfolke skoog observed that the cell division or differentiation is affected by amp and other purines a nucleic
gibberellins - plant growth substancesin late 1920s kurosawa observed that the medium in which the fungus gibberella had grown could cause the
auxins - plant growth substancesjulius sachs 1882 first suggested on the basis of his observations that there are special substances for forming
effects of plant growth regulators on developmentlike animals plants require input of energy from the outside environment to sustain growth and
reaction wood - root and shoot morphogenesisas a plagiotropic branch elongates it might be expected to bend downwards because of its increased weight
nastic and epinastic responses paratonic variation movements of plant parts in which direction of movement is independent of the direction of
geotropism - root and shoot morphogenesisroots always grow towards gravity the lot threshold of geotropic response requires as little time as one
photoreceptor - phototropismthe molecular nature of the photoreceptor is unsolved initially in the 1930s some form of carotenoid was thought to be