GROWTH OF POLLEN GRAIN NUCLEI OFTRADESCANTIA PALUDOSA

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Abstract
Pollen grain nuclei of T. paludosa Anderson and Woodson had a mean volume of 122 .mu.m3 in early G1 and 1,415 .mu.m3 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 5 days at 25.degree. C. In the 1st 3.5 days the rate of increase in mean nuclear volume was about 87 .mu.m3 per day. In the last 1.5 days of pollen grain interphase, nuclei increased at a mean rate of 658 .mu.m3 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 divided nuclei increased, mean nuclear volume decreased from 1415 .mu.m3 to 680 .mu.m3. Nuclear volumes were also determined for diploid nuclei of root meristem and sporogenous cells; their mean volumes were smaller, 1,355 .mu.m3 and 1,018 .mu.m3, than that of the G2 haploid nuclei, 1,415 .mu.m3.