Influence of growth stimulants on photosynthetic apparatus, morphogenesis and production process of eggplant (Solanum melongena)

Artificial regulation of the growth and development of cultivated plants aiming at an increase of biological productivity and improvement of the quality of agricultural products is a significant objective of modern phytophysiology. The use of natural and synthetic growth stimulators is quite effective. The present paper discusses the issue of the influence of gibberellin acid (GA3), 1-naphthylacetic acid (1-NAA) and 6-benzylaminopurine (6-BAP) on the morphogenesis and productivity of aubergine plants of Diamond variety. Field experiments were conducted in 2013–2015. The plants were treated with such growth stimulators as 1-NAA, GA3 and 6-BAP at the concentration of 0.005% using a portable sprayer. The phytometric indices were fixed every 10 days, the mesostructure was checked in the leaves of the middle layer in the phase of fruit formation, the content of the amount of chlorophylls was determined in the fresh material by spectrophotometric method, the content of different forms of carbohydrates and nitrogen in the plant organs was estimated by biochemical methods in fixed dry material. It was found that GA3 increased plant height on average by 16.3%. 1-NAA and 6-BAP practically did not change linear plant sizes. The germicides increased the number of leaves per plant (10.8–30.8%), the mass of their raw matter (19.9–47.5%) and the area of the leaf surface (17.5–42.5%). The most significant impact on these indicators was made by GA3. All the germicides increased the number of leaves per plant (14.3–20.9%). 6-BAP increased the thickness of the leaf blades by 6.3% due to the growth of chlorenchyma, and GA3 reduced it by 9.2%. Under the influence of 6-BAP and 1-NAA, the thickness of chlorenchyma was increased by 7.0% and 5.9% respectively.The upper and lower epidermis became thinner or did not change under the effects of these germicides. Under the plant treatment with 1-NAA and 6-BAP, the size of columnar parenchyma cells increased by 25.6% and 19.6% and the size of the spongiform parenchyma cells increased by 8.4–76.7%. Under the action of GA3, the cell volume of the columnar parenchyma did not change significantly, and the size of the spongy cells increased. This paper reveals that all growth stimulants reduced the number of epidermis cells (6.6–7.4%). Under the action of 1-NAA and 6-BAP, there was a decrease in the number of stomata per 1 mm2 of the abacus leaf surface, respectively,by 6.5% and 21.2%. Instead, after the use of GA3, an increase in the number of stomata was observed by 21.8%. Such germicides as 1-NAA and GA3 reduced the area of respiratory area by 11.7% and 21.4%, while the 6-BAP increased its area by 10.4%. The results of the research show that 6-BAP increased the content of the sum of chlorophylls a + b in leaves by 13.3%. Under the action of 1-NAA, this indicator had only a tendency to increase (6.7%), but under the influence of GA3 it decreased. Moreover, the processing with germicides significantly increased leaf and chlorophyll indices. All three growth stimulants have increased the mass of dry matter of plants and the net productivity of photosynthesis. The data demonstrate that growth stimulants have contributed to the accumulation of various forms of carbohydrates in the roots and fruits. In the stems and leaves there was a tendency to decrease the content of sugars and starch. The germicides significantly reduced the content of all forms of nitrogen in the roots, stems and fruits, and increased the content of protein nitrogen in the leaves. Under the action of GA3 and 6-BAP, the number of fruits per plant increased by 19.3% and 16.1%, respectively. All growth stimulants have significantly increased the average weight of the individual fetus (7.4–10.3%). As a result, the weight of the fruits from one plant after treatment with 1-NAA, GA3 and 6-BAP increased by 11.0%, 28.0% and 29.4%, respectively. There are grounds to think that growth stimulants, influencing anatomical, morphological, physiological and biochemical characteristics of aubergines, changed the nature of the donor-acceptor relationships in the plant, which intensified the production process and optimized its productivity