Changes in the physiological activity of soybean (Glycine max L. Merr.) under the influence of exogenous growth regulators

Abstract

In a two-year pot experiment (2008–2009) conducted at the Vegetation Hall, West Pomeranian University of Technology in Szczecin, we investigated the influence of exogenous growth regulators, i.e. indole-3-butyric acid (IBA) and 6-benzylaminopurine (BAP) and their mixture, on the activity of gas exchange and selected physiological features of soybeans (<em>Glycine max</em> L. Merr.). The experimental factors included the following Polish soybean cultivars: ‘Aldana’, ‘Progres’ and ‘Jutro’. During plant growth, CO<span><sub>2</sub></span> assimilation (A), transpiration rate (E), stomatal conductance (g<span><sub>s</sub></span>), and substomatal CO<span><sub>2</sub></span> concentration (c<span><sub>i</sub></span>) were determined. Two soybean cultivars, i.e. ‘Jutro’ and ‘Progres’, showed a significant increase in the intensity of assimilation and transpiration after using all kinds of growth regulators as compared with the control plants. It was found that the ‘Jutro’ cultivar, after using a mixture of growth regulators (IBA + BAP), was characterized by the significantly highest CO<span><sub>2</sub></span> assimilation (A) and transpiration (E) as well as the highest stomatal conductance (g<span><sub>s</sub></span>). The ‘Aldana’ cultivar, on the other hand, responded by a significant reduction in the transpiration rate, stomatal conductance and subsomatal CO<span><sub>2</sub></span> concentration. The spraying of the plants with exogenous growth regulators had a significant influence on the increase in the number of stomata and stomatal pore length, mostly on the lower epidermis of the lamina. It was also found that plants from the ‘Jutro’ and ‘Aldana’ cultivars sprayed with IBA and IBA + BAP were characterized by the highest yield, as compared with the control plants. In the case of the ‘Jutro’ cultivar, after using the growth regulators, a positive correlation was observed between the assimilation and transpiration rates and the length of stomata, which in consequence produced increased yields.

The Impact of Auxin and Cytokinin on the Growth and Development of Selected Crops

“…According to Nowak and Wróbel [97], fertilizers and plant protection products can no longer increase plant yields significantly, so more attention is paid to the use of various growth substances. According to the above authors, the purpose of such products is to increase plant yield potential in adverse weather or in any other unfavorable conditions not suitable for a given plant.…”

“…In particular, according to von Richthofen [98] and Ulmasov et al [99], growth-promoting substances are of great importance in the cultivation of leguminous plants, with their unstable yield and high sensitivity to weather conditions. Such substances include exogenously applied phytohormonal growth regulators used on crops and vegetables [9,97,[100][101][102][103][104].…”

“…In their studies on the effect of synthetic auxin and cytokinin and of their mixture on soybean, Nowak and Wróbel [97,103] reported a significant yield increase. According to the authors, auxin was the most effective, followed by cytokinin and their mixture, with an increase, compared to control plants, of 34, 32, and 29%, respectively.…”