TIMING OF REPRODUCTIVE ABORTIONS IN RELATION TO CELL-DIVISION, WATER-CONTENT, AND GROWTH OF PEA-SEEDS

Pod number is the most explicative component of the yield variability of pea (Pisum sativum L.). To understand the processes that determine pod number, the timing of reproductive abortion, seed development, and growth were studied. Cultivar Solara was grown in nonstressed conditions during three successive years, in 1988 and 1990 in a glasshouse in 7-L pots with 4 or 5 plants per pot, and in 1989 in the field with 50 plants m-2. At all nodes, abortion occurred before almost-equal-to 300 degree-days (base temperature of 0-degrees-C) from the date of flowering of the node; beyond this date, numbers of pods and seeds per pod remained constant at the node. During the initial 300 degree-days, embryo cellular divisions were active and then cell number plateaued. Water content varied between 0.80 and 0.86 g g-1 of fresh weight initially, then began to decrease after 300 degree-days. Seed lengths increased at a constant rate for the initial 300 degree-days and then plateaued, whereas dry weight increased slowly until 300 degree-days, but then rates increased substantially. These data indicate that seed length and water content may serve as convenient indicators to delimit the period of embryogenesis during which abortion may occur.