Quantitative and qualitative indexes of the functioning of photosynthetic apparatus of ornamental sunflower plants with different seeding rates under conditions of the Southern Steppe of Ukraine

Abstract

The research revealed the tendency for an increase in the index of the average area of an individual leaf blade when the seeding rate rose from 50 to 60 thous. pcs./ha, and further there was a reduction in this index when the seeding rate increased to 70 thous. pcs./ha. The average index in the variant of the hybrid Teddy F1 was 72.6 cm2, Double Sunking F1 - 70.3 cm2, Santa Fe F1 - 70.8 cm2, respectively. The dependence of the index of leaf blade thickness of sunflower hybrids on the factors under study was analogous: this index was minimal in the variant of the hybrid Teddy F1 - 0.58 mm, it fell to 0.55 mm in the variant of the hybrid Double Sunking F1, it was minimal in the variant of the hybrid Santa Fe F1 - 0.52 mm on the average by Factor В. According to our data, the dependence of the intensity of green color of a leaf blade of sunflower hybrids was similar: this index was not essentially dependent on Factor А, but an increase in the seeding rate caused a reduction in the intensity of green color of leaves in comparison with the sample. If the intensity of the sample color is considered to be 100%, the color of a leaf blade in the variant of the hybrid Teddy F1 was at the level of 73%, that of the hybrid Double Sunking F1 - 69%, and that of the hybrid Santa Fe F1 - 69% of the sample. The least intensity of green color of sunflower leaves was with the maximum seeding rate and did not exceed 62% on the average by Factor А. On the average by Factor В, the hybrid Teddy F1 was considered to be a leader by the content of green pigment in its leaves - 8.69 mg/g, in the variant of the hybrid Santa Fe F1 it was 7.45 mg/g, Double Sunking F1 - 8.02 mg/g. The maximum area of the crop photosynthetic apparatus was formed in the variant of the hybrid Teddy F1 being 30.7 thous. m2/ha at the stage of flowering, in the variant of the hybrid Double Sunking F1 - 29.5 thous. m2/ha and in the variant of the hybrid Santa Fe F1 - 26.1 thous. m2/ha, respectively. In all the variants of the crop hybrids there was a correlation according to which there was an increase in the index of leaf surface area when the seeding rate rose from 50 to 60 thous. pcs./ha, and when there was a further increase in the seeding rate to 70 thous. pcs./ha, vice versa, this index started decreasing considerably. The index of net productivity of photosynthesis reached its maximum values in the variant of the hybrid Teddy F1 being 1.99 g/m2/day, on the average by Factor В, that of the hybrid Double Sunking F1 - 1.93 g/m2/day and that of the hybrid Santa Fe F1 - 1.84 g/m2/day, respectively. © University of Agronomic Sciences and Veterinary Medicine of Bucharest. All rights reserved.