Characteristics of pollen production in a population of New Zealand snow-tussock grass (Chionochloa pallens Zotov).

Intraspecific variation in pollen production and pollen size were studied within a population of Chionochloa pallens, an alpine snow-tussock grass of New Zealand. I sampled plants from two sites at the altitudinal extremes (1620 and 1070 m) of the distribution of C. pallens on Mt. Hutt, South Island. There was a highly skewed distribution of pollen production among plants; the largest 10% of plants produced over a third of the pollen. In contrast to some other species, pollen production in C. pallens can be accurately estimated by simple measures such as tussock area and number of flowering shoots. Other components of yield (number of spikelets per shoot, number of florets per spikelet, and average anther length) varied significantly among individuals, but these characteristics had a small impact on total pollen yield. There was continuous variation in pollen size among individuals; between the plants with the largest and the smallest pollen grains, there was a 21 % difference in pollen diameter and a 76% difference in pollen volume. Interplant differences in pollen size have been found in a number of plants, although the biological significance of this variation is unknown. There were few differences in pollen characteristics between sites. Plants at the low-altitude site had slightly greater pollen yield because total plant size was greater.