Mortality of pollen grains may result from errors of meiosis: study of pollen tetrads in Typha latifolia L

In the cattail Typha latifolia the four haploid products of meiosis remain attached and form the flat tetrad of pollen grains. Gametophytic lethals arisen de novo in diploid cells of sporophyte must manifest themselves as pollen tetrads with two dead grains. This could allow to estimate the rate of recessive lethals arresting pollen grain development. We studied pollen samples collected from 44 sprouts in two populations in the vicinity of Novosibirsk. The anomalous tetrads T1, T2, T3, and T4 carrying one, two, three, and four dead grains, respectively, were detected in each sampled individual. The mean frequency of all anomalous tetrads in the two populations was 3.4% and 8.7%. The frequencies of tetrad classes varied widely among the individuals with correlation coefficient up to 0.94, but their ratios remained nearly constant. The majority of anomalous tetrads were presented by T1 and T2 classes (their sum comprising 72.7 and 74.0% in two populations), T1 being a little more abundant. The observed pattern of frequencies of tetrads with dead grains can be explained by errors of male meiosis such as chromosome non-disjunction in both meiotic divisions. The tetrads with two dead pollen grains may result mostly from non-disjunction in anaphase I, and those with one pollen grain from non-disjunction in anaphase II, thus making tetrad analysis ineffective for estimating the rate of gametophytic lethals.