A Morphological Study of Delaware Grape Berries

Abstract

1. The morphology of berry growth of Delaware grapes from pre-bloom to maturity was studied.2. Three distinct growth periods (I, II and III) were identified, after berry set. During period I, rapid berry enlargement occurred for 33 days. During period II, a striking decrease in growth rate occurred, and the duration of period II was very short, only about three days. During period III, the berry growth again tended to accelerate, especially in the fresh weight of berries, for 40 days.3. The increase of the inner wall tissue in the pericarp was more rapid than that of the other tissues, and was closely related to berry development.4. Inner wall tissue is constituted by cells of nearly uniform size and shape, which enlarged similarly during the growth of the berry. Outer wall tissue consists of various shapes and sizes of cells. Approximately seven layers in the external portion of the outer wall tissue become sclerenchymatous cells. Placental tissue also consists of cells of irregular shapes and sizes. The development of the placental tissue depends on the number of seeds which iarls contained in each berry.5. The last cell division in the placenta and inner wall occurred 10 days after bloom. The mean transverse berry diameter at the time of the last cell division was 3.3mm. Cell division radially in the outer wall ceased two days after the last division of the inner wall. However, the cell division in a single row in midcircumference of the outer wall continued for 19 days after full bloom. Likewise, cell division in the peripheral layer of the outer wall, the hypodermis, continued for 33 days after bloom. This means that cell division in the outer wall during the latter half of the cell division period continued only in the tangential direction and ceased earlier in the inner than outer layers.The cell division in the epidermal layer continued for 33 days after full bloom; this was as long as in the hypodermal layer. At that time the transverse diameter of the berry was 12.2mm. This was the day of period I in the berry growth curve.