Effects of High Temperature on Embryological Development and Hormone Profile in Flowers and Leaves of Common Buckwheat (Fagopyrum esculentum Moench)

Abstract

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.

Photosynthetic activity of common buckwheat (Fagopyrum esculentum Moench) exposed to thermal stress

“…The findings of this work indicate that the temperature of 30°C is more conducive to vegetative growth of common buckwheat than 20°C. Contrary to that, the higher temperature discourages generative development of this species, as showed in our earlier study (Płażek et al 2019). We claim both these outcomes crucial for researchers who try to explain the mechanism of low seed yielding in common buckwheat.…”

“…Crop plants respond to temperature depending on the optimum temperature for photosynthesis that is species specific (Downton andSlatyer 1972, Garber 1977). We have previously reported (Płażek et al 2019) that 30°C is a stress factor for generative development of common buckwheat. However, the data presented here regarding photosynthetic efficiency suggest more favourable vegetative growth of this plant species at the higher temperature.…”

“…Moreover, we demonstrated that megasporogenesis and megagametophytogenesis occurring in flowers of cv. 'Panda' were more sensitive to high temperature (30°C) than those in PA15 (Płażek et al 2019).…”

“…Hormone content analysis: Abscisic acid (ABA) and jasmonates (JAs) (jasmonic acid and jasmonic acid methyl ester) were assessed according to Płażek et al (2019). Freeze-dried and pulverized samples of donor leaves were extracted (5 min, 30 Hz, MM400, Retch, Germany) in 1 cm 3 of an extraction buffer (MeOH/H2O/HCOOH, 15/4/1, v/v/v) after addition of an internal standard solution.…”

Reducing Flower Competition for Assimilates by Half Results in Higher Yield of Fagopyrum esculentum

“…Additionally, buckwheat flowering is sensitive to many environmental stresses, including frost, heat, and drought occurring in the spring and summer despite stronger vegetative growth at 30 °C than at 20 °C [ 5 ]. A drastic reduction in the number of properly developed embryo sacs was clear in open flowers at 30 °C in cultivars ‘Panda’ and ‘Korona’ (= strain PA15) [ 5 , 6 ]. Similarly, sensitivity to the thermal stress was shown by Slawinska and Obendorf [ 1 ]; plants grown at 18 °C had by 40% increased seed set.…”