Fruit abscisic acid

Carotenoid catabolic products also have a physiological role in the plant. Oxidative cleavage of carotenoids by carotenoid cleavage dioxygenases (CCDs) generates apocarotenoids [21]. Apocarotenoids serve the plant as antifungal agents or in the synthesis of flavor or aroma of flowers and fruits. A well-known downstream product of an apocarotenoid is abscisic acid (ABA), a phytohormone in plants [21]. 

Abscisic acid, as the name suggests, has been implicated in the control of abscission of leaves, flowers and fruits, as well as with the function of stomata in response to water stress (Figure 5.4). Abscission involves the synthesis of cellulase in the ageing process and it is thought that abscisic acid influences the rate at which this proceeds. 

Kondo S, Inoue K. 1997. Abscisic acid (ABA) and 1-aminocyclopropane-l -carboxylic acid (ACC) content during growth of Satohnishiki cherry fruit, and the effect of ABA and ethephon application on fruit quality. J Hortic Sci 72 221-227. 

Last are Car precursors for important metabolites. Only three examples shall be given. The first example is retinal (Fig. 3), which is the chromophore of the visual pigment rhodopsin (23) and is derived from P,P -carotene. Because the latter cannot be synthesized by mammals, they need it to be supplied as provitamin A. Retinal derivatives are also required for other regulatory functions. The second example is abscisic acid (Fig. 3), which is the plant hormone involved in the shedding of leaves in fall and in fruit ripening it is derived from violaxanthin. Finally, certain fragrances of roses are not synthesized directly, but they are breakdown products of the flowers Cars. 

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). 

These variations in behavior indicate that harvesting melons at different stages of maturity causes subsequent biochemical events involved in amino acid accumulation to follow markedly different pathways. Recent work shows that melon fhiit harvested up to ten days before commercial maturity exhibits climacteric behavior with respect to ethylene production showing that at least this aspect of ripening is not completely inhibited by premature separation from the plant(P). However, the amount of ethylene produced is dependent on maturity at harvest and fruit harvested five days prematurely generated only about half of the amount of ethylene produced by fruit harvested two days before maturity. Also the lag time required to initiate ethylene production after harvest depended on maturity and was longer for prematurely harvested fruit. Changes in the content of the phytohormone abscisic acid were also correlated with that of ethylene. However whether the different maturity related metabolic responses observed above result from the action of these or other plant hormones awaits further study. 

Abscisic acid is a general plant-growth inhibitor. It induces dormancy and prevents seeds from germinating causes abscission of leaves, fruits, and flowers and causes stomata to close. High concentrations of abscisic acid in guard cells during periods of stress induced by drought probably have a role in stomatal closure. 

Shedding by a plant of its parts, such as leaves, flowers, fruits, or seeds. The process is regulated by the plant hormone abscisic acid, absorption coefficient... 

Abscisic acid acts as an inhibitor, is an antagonist of the other growth substances, and regulates the coloration, withering, and loss of leaves (senescence), fall of fruit, and winter rest. 

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... 

The classic P. are Auxins (see), Cibberellins (see), Antheridiogen (see), Cytokinins (see), Abscisic acid (see). Flowering hormone (see) and Fruit ripening hormone (see). 

From a biochemical perspective, with the exception of a lower level of starch in the aborting ovaries, no substantial differences between the setting and aborting ovaries were found for protein, soluble carbohydrate, RNA, or DNA, while only minor differences in the pools of free amino acids were noted [8, 12]. Abscisic acid levels in seeds and pod walls of setting and aborting pods also did not vary significantly on a tissue weight basis [17]. Contrary to that, however, ABA levels were found to be lower in bean fruits induced to set by removal of fruits lower on the raceme relative to similar fruits on intact racemes [19]. 

---