Anomalous pollen grain development after nondifferentiating microspore division in Eremurus

Anomalous pollen grain development in <i>Eremurus</i> is caused by an anomalous position of the mitotic spindle and microspore protoplast division into two cells different than in differentiating division. The nuclei of the abnormal gametophytes are always spherical and that of the smaller of the two cells, notwithstanding the shape and position of the latter, has a more compact structure resembling rather that of the generative cell nucleus. Binucleate abnormal gametophytes always have equal nuclei. The wall separating the cells in abnormal pollen grains at first contains callose and, after disappearance of the latter, probably pectins and cellulose. Abnormal pollen grains contain less cytoplasmic RNA than normal ones arid most of them degenerate. If their viability is preserved they do not form' normal pollen tubes in vitro. The frequency of anomalous microspore division is higher in <i>E. robustus</i> (max ca. 50%) than in <i>E. himalaicus</i> (max. ca. 30%) and shows considerable seasonal variations. The results obtained suggest that disturbances in microspore development in <i>Eremurus</i> have a genetic background, but are stimulated by temperature variations in the period preceding mitosis in the microspore.

Aspects of isolation underpinning mitotic behaviour in lupin protoplasts

This study reports on the influence of critical isolation factors on the subsequent culture of protoplasts of Lupinus albus L. Protoplasts were isolated from in vitro seedling cotyledons of five early maturing accessions in which protoplast yields and division frequencies appeared to be correlated as a high protoplast yield corresponded with a high division frequency. The overall difference among the accessions for mitosis was non-significant, although the highest yield and division frequency were observed in accession LA132, with Alban giving a significantly lower level. Accession Lucrop produced the lowest number of protoplasts, all of which collapsed during culture. Of the enzyme types used for tissue maceration, Pectolyase Y23, was significantly inferior to Macerase in terms of giving way to mitosis. The extent of division in Macerase-isolated protoplast population was 266% higher than that in the Pectolyase Y23-isolated one. The physiological maturity level of the explant, expressed in terms of developmental age, was optimal when 14–18-day-old seedling cotyledons were used for protoplast production and culture, rather than more mature ones, despite higher protoplast yields in the latter. On K8p medium, the protoplast division frequency was 129% greater when 18-day-old seedling cotyledons were used, than that with any other treatment. This work on protoplast culture of the potentially important lupin species, which is a pulse rich in dietary protein, oil and fibre, allows a further understanding of the biology, with an aim to advance lupin biotechnology.