Para-aminobenzoic acid stimulats seed germination, plant growth, development, photosynthesis and nitrogen assimilation in the amaranth (Amaranthus L.)

Currently protective, reparative, anti-mutagenic, antioxidant properties of para-aminobenzoic acid (pABA) are described. The huge number of the facts is saved up concerning its efficiency on all elements of yield structure of different plants species and household purposes. However, there is almost no information about the effect of pABA on amaranth plants in the world literature. Vegetable amaranth is a valuable food culture, promising to Central Russia. Therefore, we are especially interested in ways to facilitate its introduction, increase productivity, and nutritional value. To this end, it is possible to use pABA as environmentally friendly biologically active natural compound with a broad spectrum of action. In this work, we first investigated the effect of pABA on seed germination, and growth, development and productivity of vegetable amaranth Amaranthus caudatus L. variety K173 (K173) and A. cruentus L. variety K185 (K185) of grown plants as well as on light-dependent processes of photosynthesis and nitrogen assimilation in the leaves. To assess the characteristics and level of pABA activity the experimental results concerning influence of a synthetic citokinin 6-benzilaminopurin (6-BAP) on the same parameters are given. A dependence of amaranth seed germination on pABK 10-9 М to 10-4 М concentration used for treatment was found. The seed germination in both varieties was 23±5 % higher at 10-6 M pABK, whereas 10-4 M pABK decreased it by 22±4 %, and other concentrations had no significant effect. In K173 the 15-day seedlings exceeded the control by 10±5 % in height, by 76±6 % in weight, and by 133±17 % in root length at the latent growth stage. Parameters of K185 plants were slightly higher. The acceleration of plant development may contribute to survival and adaptation. Stimulating effect of pABA on К173 and К185 plant growth in height is maintained for the life of plants, except initiation of generative organs (days 60-80). A significant increase (30-85 %) in plant weight compared to control was identified at all stages of ontogenesis. Productivity of leaf biomass per plant in both varieties on day 115 was on average 50±11 % more than in the control. In the leaves of 45-day plants of К173 grown from treated seed, the activity of nitrate reductase increased by 37±4 % and the total protein level was 10±3 % higher when compared to control, thus improving nutritional value of the culture. The rate of photophosphorylation in chloroplasts was shown to be 27±6 % higher, and the rate of electron transport was 32±6 % higher in comparison with the control that led to an increase in leaf net photosynthesis by 22±7 %. These were no different from 6-BAP effects. The pABA influence on the seed germination and plant biometric parameters in K173 and K185 was comparable to the action of 6-BAP. pABK influenced nitrate reductase activity, protein level, chlorophyll content, and photophosphorylation rate in leaves of K173 plants much weaker, than 6-BAP, and differed from it. The pABA properties as a plant hormone are discussed, and the use is recommended for the vegetable amaranth cultivation.