Ciclo di Accrescimento e Differenziazione delle Gemme in Piante Perenni Nel Territorio di Bari

Summary

Growth CYCLE AND BUDS DIFFERENTIATION IN PERENNIAL PLANTS GROWING IN Bari AREA. 2) OBSERYATIONS ON Prunus AMYGDALUS STOKES DURING THE YEAR 1946.

As explained in the diagr. 1, the growth period of the six shoots of an almond-tree under observation at Bari during 1946 lasts from middle March as late as middle May, that is about two months.

The growth reaches its highest speed during the month of April (diagr. 2). We may thus assume that climatic factors during this month were the most favorable for the tree-growing.

During the month of May, while temperature was rising, rain was pratically absent and rainless weather lasted as late as October. The vegetative growth has been evidently stopped by the summer drought.

No retaking of the vegetative growth has been observed after the summer drought period (diagr. 1).

The morphological differentiation of the flower parts initiated into the flower bud at the middle of August, lasting about two months. Neverthless some external changes can be observed in the flower bud from the middle of May (cfr. fig. 1 to fig. 3), while at the end of July some changes occur in the bud apical meristem (fig. 4).

The flower bud differentiation begins with a sudden stopping in the developement of the meristematic leaf nodules along the apex. The last formed leaf initials loose their meristematic character, being left as little protuberances along the meristematic apex (figg. 7 and 8). The apex, which was papillar shaped (fig. 6), flattens upperwards (figg. 8 and 7), and successively it sinks becoming cup-shaped (figg. 9 and 10). The different floral parts start their differentiation, procceding from the edge of the cup as far as its bottom. The first differentiates the calyx, then the corolla and the stamens verticills; the last the ovary (fig. 11).

In the second half of October, the flower is completely formed (fig. 12) and its growth and histologic differentiation takes place (fig. 13). At the end of the pollen grains are already formed, while the ovules are not yet full developed (fig. 14).