The biased ratio (1 : 2.7–1 : 19) of long-styled Pin and short-styled Thrum flowers (anisoplethy) in common buckwheat (Fagopyrum esculentum) with low seed set (9.8–33.1%) is documented for the first time in two cultivars (Kora, Panda) and two strains (PA13, PA14). To establish the reasons for low grain yield we studied pollen, embryo sacs, embryos, counted stigmas with compatible pollen and with compatible pollen tubes, and recorded seed set under semi-controlled conditions with open access of pollinators. We also sought to improve seed yield via exogenous application of eight biostimulants at the beginning of flowering. Pin pollen supply to Thrum stigmas was low, due to the imbalance of flower morphs. This did not affect seed set or male success in either flower morph. The pollen of Pin or Thrum was highly viable (97.9–99.9%) in all studied cultivars and strains, germinating well on compatible stigmas. The female success of both flower types was much lower; 49–59% of the ovules exhibited signs of degeneration (whole flower buds, ovules only) or abortion (mature embryo sacs, proembryos, embryos); the highest share of mature embryo sac abortions resulted from degeneration of synergids or the whole egg apparatus. Three biostimulants (Gibberellic acid, putrescine, Asahi SL) in PA13 and six (1-Naphthaleneacetic acid, Gibberellic acid, TYTANIT, putrescine, 6-Benzylaminopurine, Asahi SL) in PA14 decreased embryo abortions (4–12 fold) and increased seed set (0.4–2.4 times), but seed set was still low and never exceeded 33% (the highest value of the untreated with biostimulants plants). Biostimulant treatments were most effective on PA14 strain increasing seed set in 7 out of 8 treatments. These were Gibberellic acid, putrescine and Asahi SL improving seed set of two among four analysed genotypes.

Common buckwheat is a valuable crop, mainly due to the beneficial chemical composition of its seeds. However, buckwheat cultivation is limited because of unstable seed yield. The most important reasons for the low yield include embryo and flower abortion. The aim of this work is to verify whether high temperature affects embryological development in this plant species. The experiment was conducted on plants of a Polish cultivar ‘Panda’ and strain PA15, in which the percentage of degenerating embryo sacs was previously determined and amounted to 32% and 10%, respectively. The plants were cultivated in phytotronic conditions at 20 °C (control), and 30 °C (thermal stress). The embryological processes and hormonal profiles in flowers at various developmental stages (buds, open flowers, and wilted flowers) and in donor leaves were analyzed in two-month-old plants. Significant effects of thermal stress on the defective development of female gametophytes and hormone content in flowers and leaves were observed. Ovules were much more sensitive to high temperature than pollen grains in both genotypes. Pollen viability remained unaffected at 30 °C in both genotypes. The effect of temperature on female gametophyte development was visible in cv. Panda but not in PA15 buds. A drastic reduction in the number of properly developed embryo sacs was clear in open flowers at 30 °C in both genotypes. A considerable increase in abscisic acid in open flowers ready for fertilization may serve as a signal inducing flower senescence observed in the next few days. Based on embryological analyses and hormone profiles in flowers, we conclude that cv. ‘Panda’ is more sensitive to thermal stress than strain PA15, mainly due to a much earlier response to thermal stress involving impairment of embryological processes already in the flower buds.

Seed imbibition under cold temperature is dangerous when dry seeds have relatively low water content. The aim of this study was to investigate germination of 20 lines/cultivars of narrow-leaf lupine at 7 °C (cold) and 13 °C (control) under the influence of smoke water and following seed hydropriming for 3 h at 20 °C. The efficacy of individual treatments was examined with regard to seed protection during low-temperature germination. Based on seed germination, vigour at cold was evaluated four days after sowing by means of hypocotyl length, the studied lines/cultivars were divided into three groups with low, high and very high germination rates. Germination vigour correlated with cell membrane permeability, dehydrogenase activity and abscisic acid (ABA) content and was analysed in the seeds one day after sowing. Gibberellin content did not correlate with germination vigour. The seeds of weakly germinating lines/cultivars had the highest cell permeability and ABA content as well as the lowest amylolytic activity at both studied temperatures. Additionally, the vigour of weakly germinating seeds at 7 °C correlated with dehydrogenase activity. Three-hour hydropriming was the most effective for seed germination under cold due to reduced cell membrane permeability and ABA level. Stimulating effects of smoke water on germination under cold could be explained by enhanced dehydrogenase activity.