Rest andactivityinvegetativebuds of treesP.ChampagnatrueLaboratoire de

Rest andactivityinvegetativebuds of treesP.ChampagnatrueLaboratoire de Phytomorphog6n6se, Universite Blaise-Pascal, 4, Ferrand, FranceLedru, F-63000, Clermont-IntroductionRest of buds, particularly on trees or shrubs, may have 3 different origins: 1)unfavorable environmental conditions (for instance low temperatures); in this case, the bud is called ’quiescent’; 2) correlative inhibitions exerted by other organs or parts of the plant, more or less distant from the considered bud. Those may be called ’long distance correlative inhibitions (LOis)’; the apical dominance exerted by the terminal bud over axillary buds on growing shoots is the most studied example of LDI; 3) some intrinsic properties of the bud itself, such as...
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Rest andactivityinvegetativebuds of treesP.ChampagnatrueLaboratoire de Rest andactivity invegetativebuds oftreesP.ChampagnatrueL aboratoire de buds of trees inRest and activity vegetativeP. Champagnat Ledru, F-63000, Clermont-Laboratoire de Phytomorphog6n6se, Universite Blaise-Pascal, 4, rueFerrand, France For over 50 years, investigations on budIntroduction rest have mainly focused on plant growth regulators, and their possible involvementRest of buds, particularly on trees or in apical dominance or in dormancy. Theyshrubs, may have 3 different origins: 1) did not lead to generally acceptedunfavorable environmental conditions (for conclusions (Samish, 1954; Champagnat,instance low temperatures); in this case, 1965; Wareing and Saunders, 1971;the bud is called ’quiescent’; 2) correlative Phillips, 1975; Saunders, 1978; Hillman,inhibitions exerted by other organs or 1984). A few papers (Vegis, 1964; 1965a,parts of the plant, more or less distant and Usciati Guern 1975; 1972; b;from the considered bud. Those may be Mcintyre, 1977) and 1974; Miginiac,called ’long distance correlative inhibitions especially recent reviews by Mauget(LOis)’; the apical dominance exerted by (1987), Tamas (1987) and Powel (1987)the terminal bud over axillary buds on have emphasized the necessity of settinggrowing shoots is the most studied the problem on much wider biochemicalexample of LDI; 3) some intrinsic prop- and physiological bases. That will be theerties of the bud itself, such as when the aim of the present paper, with emphasisbud remains at rest even if all usual on the following aspects: 1) the structuralsources of correlative inhibition have been complexity of a bud, and the tightness ofremoved and if environmental conditions its connections with its bearing axisare favorable; in this case, the bud is (Champagnat, 1988); 2) the state ofcalled ’dormant’ (Champagnat, 1983). nutritional deficiency of a resting bud, In fact,taking into account the structural either during dormancy or during cor-complexity of most buds, and the strong relative inhibition of growth, and the factinterrelationship they maintain with their that, during growth recovery, the differentshoot axis, we will show that the rest of deficiencies are eliminated in a precisethe meristematic region and related and determined order; 3) the shorttissues depends upon ’short distance distance control (SDI) of nutrient fluxesinhibitions (SDIs)’ exerted either by the towards the meristem cells in buds, bybud’s basal tissue or by the adjacent changes in membrane permeability ofshoot-axis tissues. some adjacent but distinct cells; 4) the fact a modification of the lipid composition ofthat this latter SDI is strongly related to the plasmalemma, which in turn causes alonger distance correlations (LDI during ) Snormal inhibitions, whereas it is acting modification of membrane permeabilityalone and is very stable during true (Usciati et al., 1974). Moreover, change a in membrane-bound Mg ATPases is + 2dormancy. rapidly set in motion and the cation We will examine 4 examples which have content of cells is altered (Habricot andbeen the subject of recent work, Sossountzov, 1984; Sossountzov andparticularly in France: apical dominance, Habricot, 1985; Sossountzov et al., 1985).rhythmic growth of oak seedlings, and Near the insertion point of the axillaryinduction and release of dormancy in buds bud on its axis, that is near its base, anon trees and on some tubers, the latter inversion of the polarity of cells inshowing physiological and biochemical conducting or proconducting tissues hasfeatures which may be compared to those been observed by many authors. Theof tree buds. transverse permeability of these cells is ...