Growth during microsporogenesis in hexaploid triticale

Abstract

During the 100-h period from quartet breakup until first pollen grain mitosis, mean cell, nuclear, and nucleolar volumes were calculated at 10-h intervals in hexaploid triticale (× Triticosecale Wittmack cv. Rosner). Changes in DNA content per microspore were also measured to determine the time of DNA synthesis. From 0 to 30 h (G1), (1) cell volume increased at a constant rate from 9400 to 48 297 μm3, (2) nuclear volume initially increased from 1674 to 3261 μm3 but then returned to 1568 μm3. and (3) nucleolar volume did not change. From 30 to 70 h (S), cellular volume increased to 79 090 μm3, nuclear volume did not change, and nucleolar volume initially increased twofold but then returned to the G1 value. From 70 to 100 h (G2), there was no change in cell volume, while nuclear and nucleolar volumes increased to 4365 and 344 μm3, respectively. Regression analysis throughout microsporogenesis indicated a constantly changing significant relationship between the volume of a cell and its nucleus and nucleolus. However, no significant regression coefficients were obtained during early prophase. These results are interpreted as indicating that critical cellular, nuclear, or nucleolar volumes are not necessary for the development of a cell through interphase.