Influence of photosynthetic apparatus on the productivity of high-oleic sunflower depending on climatic conditions in the left-bank forest-steppe of Ukraine

Andrii Melnyk, Jones Akuaku, Tetiana Melnyk and Anton Makarchuk

Abstract: The influence of chlorophyll content and leaf surface area on crop productivity is acknowledged but information regarding these impacts on sunflower productivity is scanty. Also, the correlation between sunflower leaf surface area and chlorophyll content is largely unknown. Moreover, it is unclear the extent to which the leaf surface area and chlorophyll content influence sunflower productivity. Environmental conditions can also limit sunflower development and productivity. Hence, a two year (2016-2017) field experiment was conducted with the high-oleic sunflower hybrid PR64H32 under the environmental condition of the Left-bank forest-steppe of Ukraine. Analysis of weather conditions, particularly Hydrothermal coefficient (HTC) established that the vegetative period of 2016 had a normal moisture (HTC =1.00), while the year 2017 was dry (HTC = 0.45). Phenological observations revealed that generally, the vegetation period in 2016 was 120–122 days whereas that of 2017 was 115-117 days. In 2016, there was a significantly (P < 0.05) higher plant height, stem diameter, number of leaves, number of seeds per head and seed weight per head than in 2017. In contrast, both absolute chlorophyll concentration “a” and “b” and relative chlorophyll content (SPAD-502 plus readings) were higher in 2017 but there was no significant difference compared to 2016. Insufficient rainfall in 2017 caused a shortage in yield (seed weight per head) by 23.4%. Determination of seed quality with Spinlock Magnetic Resonance Solutions resulted in an oil content of 49.5% in 2016 but a slightly higher value (50.4%) in 2017. On the contrary, oleic acid content reduced from 81.6% in 2016 to 76.4% in 2017. Regression analysis uncovered an inverse proportional relationship between sunflower leaf surface area and the chlorophyll content (correlation coefficient, r = 0.67). Further analysis provided compelling evidence that, the leaf surface area impacted significantly on sunflower productivity (seed weight per head) than the chlorophyll content – a major interest in sunflower production.

Keywords: forest-steppe; high-oleic; leaf surface; photosynthetic apparatus; sunflower

Date published: 2020-08-28