Abscisic acid and ethylene

Recently, another role for ABA-cytoskeleton interactions was discovered in guard cells of Vida faba leaves [150]. ABA specifically disrupted the MTs in guard cells but not in other epidermal cells. This effect resulted in the closure of stomata. When MTs repolymerized, the stomata reopened. Interestingly, no other plant hormone could elicit such a response in the guard cells. Actually, a role for MTs in the stomata closure-opening mechanism had been proposed earlier on the grounds that the MT-disrupter, colchicine, inhibited stomatal opening in Tradescantia leaves [151]. 

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An interesting effect of Aceria attack on the abscisic acid and ethylene content in the fruits was recorded. This stressor increased the highest values of stimulating phytohormones also. These substances can disturb the dormancy and cause the highest germinability (Fiserova et al., 1999). 

PLD plays important roles in the response to wounding and other stresses through mediating the actions and production of stress hormones [140]. PLDa is specifically involved in the actions of abscisic acid and ethylene in plant senescence and in the control of water loss [140, 141]. Different stresses in plants lead to different expression patterns for PLD isozymes. 

Until the discovery of brassinolide by USDA scientists in 1979, it was thought that only five groups (indole auxins, gibberellins, cytokinins, abscisic acid, and ethylene) of hormones were responsible for regulating plant growth and development. Following this discovery, a number of compounds similar to brassinolide both in structure and physiological activity were isolated from different parts of plants. On the basis of published... 

It is also possible that the five known major hormone classes can be subdivided. Particularly, the plethora of different gibberellins now known may in the future be grouped into different subsets functioning in the same plant. Furthermore, it is probable that indoleacetic acid, zeatin, abscisic acid and ethylene are not the only active hormones in their classes. 

Letham DS (1971) Regulators of cell division in plant tissues. XII. A cytokinin bioassay using excised radish cotyledons. Physiol Plant 25 391-396 Libbenga KR, Xorrey JG (1973) Hormone-induced endoreduplication prior to mitosis in cultured pea root cortex cells. Am J Bot 60 293-299 Lieberman M, Kunishi AX (1971) Abscisic acid and ethylene production. Plant Physiol 47, Suppl, p 22... 

The mechanism of action of lAA in the inhibition of leaf shedding is a matter of dispute. The problem is further complicated by the fact that lAA can also stimulate leaf shedding under certain conditions. Apart from this special effect of lAA there are also substances that universally promote the shedding of leaves abscisic acid and ethylene. Their mechanism of action is somewhat better understood (page 211). Perhaps they will provide a means to elucidate the mechanism of action of their antagonist lAA. 

I04"C) is often considered as a plant growth substance because it acts like a fruit-ripening hormone. The biosynthesis of ethylene in the plant from 1 -ami-nocyclopropanecarboxylic acid is stimulated by auxins abscisic acid and cytokinins can - depending on the type of plant - have stimulating or inhibiting effects, and tissue injuries in plants lead to the formation of the so-called wound ethylene . For information on the numerous roles of ethylene, see Other... 

Many studies have suggested that BRs play essential roles in responding to various stresses such as abnormal temperatures, drought, high osmotic pressure, and pathogen attacks [81, 82]. The occurrence of cross-talk between BRs and stress-responsive hormones such as abscisic acid, jasmonic acid, and ethylene is consistent with the suggestion that BRs play an important role in plant stress responses [83]. 

There are few specific studies of the effects of gibberellins, ethylene, abscisic acid, and other growth regulators on the cell cycle. While these substances have effects on division in some instances, evidence connecting these effects to specific steps of the cell cycle is generally lacking. 

Andreae WA, Venis MA, Jursic E, Dumas T (1968) Does ethylene mediate root growth inhibition by indole-3-acetic acid Plant Physiol 43 1375-1379 Anker L (1973) The auxin production of the physiological tip of the Avena coleoptile and the repression of tip regeneration by indoleacetic acid (not by naphthylacetic acid and 2,4-dichlorophenoxyacetic acid). Acta Bot Neerl 22 221-227 Anker L (1975) Auxin-synthesis inhibition by abscisic acid, and its reversal by gibberellic acid. Acta Bot Neerl 24 339-347... 

Enu-Kwesi L, Dumbroff EB (1977) Changes in abscisic acid and other inhibitors in seeds of Acer saccharum during stratification. Plant Physiol 59 Suppl, p 76 Ernest LC, Valdovinos JG (1971) Regulation of auxin levels in Coleus blumei by ethylene. Plant Physiol 48 402-406... 

Kohler K-H, Dorfler M, Goring H (1980) The influence of light on the cytokinin content of Amaranthus seedlings. Biol Plant 22 128-134 Kondo K, Watanable A, Imaseki H (1975) Relationships in actions of indoleacetic acid, benzyladenine and abscisic acid in ethylene production. Plant Cell Physiol 16 1001-1007... 

Mayak S, Dilley DR (1976) Regulation of senescence in carnation Dianthus caryophyl-lus) Effect of abscisic acid and carbon dioxide on ethylene production. Plant Physiol 58 663-665... 

Rappaport L (1979) Does GA3 regulate cell division Plant Physiol 63 Suppl, p 32 Rauser WE, Horton RF (1975) Rapid effects of indoleacetic acid and ethylene on the growth of intact pea roots. Plant Physiol 55 443-447 Rehm MM, Cline MG (1973) Rapid growth inhibition of Avena coleoptile segments by abscisic acid. Plant Physiol 51 93-96... 

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