Ciclo Di Accrescimento e Differenziazione Delle Gemme in Piante Perenni Nel Territorio Di Bari

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Abstract
Growth CYCLE AND BUDS DIFFERENTIATION IN PERENNIAL PLANTS GROWING IN Bari AREA. 1) Observations ON Ficus Carica DURING THE YEAR 1946. The fig tree under observation in Bari started its growth (during the year 1946) in the second week of March and stopped in June second half. The growth period lasted about three months (tab. 1 e 2; diagr. 1). The most rapid growth occurred during the second week of May (tab. 2; diagr. 1). From the diagr. 3 it appears that in the fig tree the growth end corresponds at the beginning of the rainless weather; in the meantime the temperature rises gradually (diagr. 4). The atmospheric humidity subsists high also during the summer rainless period (diagr. 5). Among the four shoots examinated, only one showed a further slow lengthening (13 mm.) from 2nd. August to 6th September. The three others did not grow anymore from June 15 (tab 2; diagr. 1). The young shoot internodes have different lengths. The basal ones are shorther than the middle ones, which appeared during this speedly growing period (diagr. 2); the last two internodes are very short, so that the nodes are rather contiguous. At each node one leaf unfolds, with two large stipules, which soon fall; on the very last node the stipules do not fall, sheltering the young apical bud, which they completely close in. The corresponding leaflet scarsely grows, falling soon. Neverthless the protection of the two stipules, the first leaflet of the apical bud withers and falls frequently as soon as the bud unfolds at the beginning of spring (fig. 1). Each leaf axil bears two or three buds (fig. 7). When two buds are present, one is a fruit bud and the second a vegetative one (figg. 11 e 13), when three buds are present, the two lateral ones develop into flowers, while the middle one grows into a vegetative shoot (fig. 12). The very first sign of the fruit character of a bud is the flattening of the apical bud meristem (fig. 7); successively it deeps into a cuplike body (figg. 8 and 9); on the bottom and along the walls of the cup the female floscules are developing (fig. 10). The first sign of the vegetative character of a bud is, after the formation of the leaf meristem outline, its evolution with the caratteristically lobed leaves and stipules. As far as a given height along the shoot (as far as the sixth node in our shoots) the syconia prolong their growth after the shoot lengthening has stopped and ripen completely during August-September (forniti or September-figs). From a certain level ahead, as far as the apical bud (from the seventh to the tenth node in our shoots) the syconia cease their development about contemporarly the vegetative shoot. They are three or four mm. wide and the little flowers are clearly distinguishible inside. So they hang from the nodes as late as next spring time, when they begin to grow again, ripening in June (fioroni or June-figs). September and June figs then represent a continous acropetal fruit series differentiating at each leaf axil, as soon as the leaflets unfold during the shoot development. We must point out that while the September figs reach the ripe condition through a stopless development in the same year, the June figs stop their growth at a given time, standing a resting period and begin to grow again, ripening the next vegetative season. As to explain such a behaviour, the presence of an inhibitory stuff is prospected, produced from the more developed figs, which attain a given stadium of development. This stuff would act on those figs, which have not yet reached this particular development stage. The summer drought checkes the shoot growth and the bud differentiation. The flower buds, which have been too early stopped in their development, are not able to grow again the next season and fall during the apical bud unfolding. Such a condition occurs in the last leaf bud (fig. 4) and in the first leaflet bud inside the vegetative tip (apical bud) (fig. 5). At the beginning of the new vegetation season the shoot awakes with the differentiation of those buds, which did not yet differentiate at the axil of the leaflets inside the apical bud (fig. 6). (See fig. I, where the phenomenon is schematically reproduced).

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