GROWTH OF POLLEN GRAIN NUCLEI OF TRADESCANTIA PALUDOSA

Abstract

Pollen grain nuclei of Tradescantia paludosa Anderson and Woodson had a mean volume of 122 μm3 in early G1 and 1,415 μm3 in late G2. The distribution of nuclear volumes was not linear normal; however, it closely approximated a log normal distribution and probit plots yielded straight lines for the central 85-90% of the values. Most nuclei were spherical or nearly-spherical in early G1 but their increase in volume was accompanied by a change to an ovaloid or elongate shape. Interphase in the pollen grain lasted about five days at 25 °C. In the first 3.5 days the rate of increase in mean nuclear volume was about 87 μm3 per day. In the last 1.5 days of pollen grain interphase, nuclei increased at a mean rate of 658 μm3 per day; nuclear growth was relatively slow in G1 and rapid in G2. The largest nuclei tended to divide first; the result was that as the proportion of nuclei that have divided increased, mean nuclear volume decreased from 1415 μm3 to 680 μm3. Nuclear volumes were also determined for diploid nuclei of root meristem and sporogenous cells; their mean volumes were smaller, 1,355 μm3 and 1,018 μm3, than that of the G2 haploid nuclei, 1,415 μm3.