Leaf water-use efficiency parameters of Fagopyrum esculentum Moench plants as influenced by endogenous and exogenous factors

Sustainable development of contemporary agriculture is hampered by a number of facotors, one of which is the increasing aridization of the planet’s climate. In this regard, the water use efficiency (WUE) of plants is of great importance. In this paper the data of long-term field experiments are submitted which illustrate the influence of photosynthesis rate, transpiration rate, stomatal conductance and, also, growing conditions on the buckwheat plant WUE. The purpose of the study is to identify the specific peculiarities of WUE of common buckwheat ( Fagopyrum esculentum Moench) plants with regard to photosynthesis and production processes. A total of 22 varieties of common buckwheat (K-406 and K-1709 - local populations; Kalininskaya, Bogatyr, Shatilovskaya 5 - old varieties; Dikul, Dozhdik, Demetra, Devyatka, Design - modern commercial varieties; Bashkirskaya krasnostebelnaya, Batyr, Usha, Chatyr-Tau, Inzerskaya, Design 2, P 66, P 69, P 70, P 84, P 85, SPR 52 - varieties which are perspective for different conditions) were examined. Plants were grown on the experimental field of buckwheat breeding lab of FSC of Legumes and Groats Crops (Orel District, Orel Province) in 2010-2015. A plot area was 10 m2. The plots’ locations were random, with fourfold replication. Photosynthesis rate (PI), transpiration intensity (TI), and stomatal conductance were measured according to the original method of Heinz Walz GmbH (Germany) using a GFS-3000 FL portable gas analyzer. The assessment was conducted on 5-7 plants typical for the genotype, growing in the middle of the plot, which leaves were not damaged by pests and diseases. The measurements were carried out in real time at the main growth phases (branching, flowering + 10 days, flowering + 20 days, flowering + 30 days) from 7 AM to 7 PM with a frequency of 3 hours. In the measuring chamber of the device the light intensity was maintained at 1000 μmol photons·m-2·s-1, the air temperature was 25 °С. The measurements were performed on the 3rd leaves from the top. WUE was calculated as the ratio of the values of the photosynthesis and transpiration intensities. The grain yield from each plot was evaluated both by direct weighing and by structural analysis of plants. As a result of the research, it was found that the buckwheat WUE values significantly depend on both growing conditions and hereditary characteristics. Depending on the weather conditions of the growing season, the WUE varied from 1.03 to 2.08 μmol CO2/mmol H2O. Its highest value (2.08 μmol CO2/mmol H2O) was noted in 2012 when the weather was relatively favorable for plant growth and development. In ontogeny, the maximum efficiency of water use for the photosynthesis was recorded at branching (2.43 μmol CO2/mmol H2O on average) and mass filling of seeds (1.78 μmol CO2/mmol H2O/m2s), and the lowest WUE values were during budding and flowering (1.17 μmol CO2/mmol H2O on average). In the daytime, the most CO2 molecules per unit of evaporated water were assimilated from 9 AM to 11 AM when the highest intensity of leaf photosynthesis and moderate transpiration activity were observed. The correlation coefficient between WUE and the intensity of leaf photosynthesis was positive ( r = 0.69, p function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }