Dormancy of buds

Dormancy of Buds. As the autumn days become shorter the shoots of our woody plants switch over to the state of dormancy. During the shortened day-time inhibitors such as abscisic acid (Fig. 167) concentr-... 

Abscisic acid is a terpenoid (Fig. 171). Abscisic acid is the name recently proposed. In addition, the older names dormin and abscisin II are still in use. Dormin refers to the fact that abscisic acid brings about the dormancy of buds and abscisin to the fact that abscisic acid can promote the shedding of leaves and fruit. Abscisic acid seems to be ubiquitous in the plant kingdom. Chemically closely related substances exhibiting, to some extent, a similar effect have also been detected repeatedly. 

The tests for abscisic acid (= abscision II = dormin) are based on the inhibition of growth, the stimulation of the shedding of leaves and fruit, the induction of the dormancy of buds and the inhibition of seed germination, to mention only the most important. 

Initiate or terminate the dormancy of seeds, buds, and tubers. 

ABA was originally discovered because of its role in the dormancy of apical buds [20]. The correlation between the amount of ABA in apical buds and the depth of winter dormancy suggests that ABA plays a major role in the dormancy of this region. More controversial is the question as to whether ABA is involved in lateral bud dormancy as well [85]. Another major role of ABA is to induce the dormancy in maturing seeds of many species. At the same time, ABA induces the synthesis of proteins stored in seeds as... 

In a number of processes, including the induction of a-amylase in barley aleurone cells, the control of stem elongation and the dormancy of apical buds and seeds, ABA has the ability to counteract the specific effects of GA [30]. In other processes such as stomatal closure, the action of ABA is independent of GA [87]. 

In addition to the mechanisms of stress response so far considered, there are several others which have attracted the attention of plant ecologists. These include innate or environmentally determined forms of dormancy in seeds, spores, and vegetative buds, many of which represent adaptive responses restricting plant growth and development to favourable seasons or sites. Dormancy has been the subject of numerous publications and will not be considered here. Instead, opportunity will be taken to refer to two forms of plant response to stress which until recently have received only scarce attention. The first is the phenomenon of stored growth whilst the second involves the response of the developing shoot to mechanical impedance. 

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