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Higher yielding varieties of common buckwheat (Fagopyrum esculentum Moench) with determinate growth habit (single mutation det) manifest higher photosynthesis rate at stage of grain filling Abstract: Comparison of common buckwheat varieties with determinate vs. indeterminate growth habit reveals no differences in leaf photosynthesis rate at stage before flowering. However, at stage of seed filling the difference was significant. Maximal difference was 20 days after early flowering, i.e in period of most intensive seed formation. These results show that determinate varieties have higher sink strength providing by developing seeds. It is correlated with higher yield ability of such varieties. Probably, growth limitation resulting from det-mutation leads to some shifts in system of sink priorities of buckwheat plant and allows initiate the development of additional seeds. One more possible cause of alteration of the physiological parameters in determinate varieties is some optimization of plant structure: in terms of physiology the determinate buckwheat is a plant which is more similar to cereals than indeterminate buckwheat. However, underlying physiological changes accompanying the transition from indeterminate toward determinate growth in buckwheat remain almost unknown. Assumption about strong effect of det-mutation per se on photosynthesis rate was not supported in our work. Alternative assumption about accumulation of additional genes enhancing the sink ability suggests opportunities for additional progress in the selection work using tools evaluating photosynthesis intensity at stage of grain filling. Bolj donosne sorte navadne ajde (Fagopyrum esculentum Moench) z determinantno rastjo (enojna det mutacija) imajo večjo fotosintezo v fazi polnjenja zrnjaIzvleček: Primerjava sort navadne ajde z determinantno in nedeterminatno rastjo ne kaže razlik v fotosintezi listov v fazi pred cvetenjem, vendar je razlika v fazi polnjenja zrnja značilna. Največja razlika je bila20 dni po začetku cvetenja, to je v fazi najbolj intezivnega oblikovanja semen. Ti izsledki kažejo, da imajo determinantne sorte večjo moč ponora, ki jo dajejo razvijajoča se semena. To je povezano tudi s sposobnostjo večjega pridelka teh sort. Verjetno je omejitev rasti posledica det-mutacije, kar vodi v nekatere premike v sistemu prioritet ponora v rastlinah ajde in, kar vzpodbudi razvoj dodatnih semen. Nadaljni možni vzrok v spremembi fizioloških parametrov determinatnih sort je v optimizaciji zgradbe rastline, determinatna ajda je v fiziološkem pogledu bolj podobna žitom kot pa nedeterminatni ajdi. Kljub vsemu, pa ostajajo fiziološke spremembe, ki spremljajo prehod od nedeterminantne k determinatni rasti skoraj popolnoma neznane. Domneva o močnemu činku det-mutacije per se na fotosintezo v našem delu ni bila potrjena. Alternativna domneva o kopičenju dodatnih genov, ki pospešujejo sposobnost ponora daje priložnosti za nadaljni napredek pri selekcijskem delu z uporabo ovrednotenja jakosti fotosinteze kot orodja v fazi polnjenja zrnja.

Genotypic aspects of leaf transpiration intensity manifestation in 22 buckwheat varieties from different periods of creation were studied in the field in real time on intact plants. It is shown that their ability to evaporate water has a high hereditary conditionality and plays an important role in increasing photosynthetic activity and crop productivity in the breeding process. Based on this, it is concluded that when creating new varieties, it is very important not only to carry out current control over the state of this process, but also to carry out targeted selection on it, considering photosynthesis activity. In this case, it is necessary to select forms that combine high intensity of leaf photosynthesis with moderate transpiration activity.

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