Effect of Plant Growth Regulators on Protease Activity in Forest Floor of Norway Spruce Stand

Soil proteases are involved in organic matter transformation processes and, thus, influence ecosystem nutrient turnovers. Phytohormones, similarly to proteases, are synthesized and secreted into soil by fungi and microorganisms, and regulate plant rhizosphere activity. The aim of this study was to determine the effect of auxins, cytokinins, ethephon, and chlorocholine chloride on spruce forest floor protease activity. It was concluded that the presence of auxins stimulated native proteolytic activity, specifically synthetic auxin 2-naphthoxyacetic acid (16% increase at added quantity of 5 μg) and naturally occurring indole-3-acetic acid (18%, 5 μg). On the contrary, cytokinins, ethephon and chlorocholine chloride inhibited native soil protease activity, where ethephon (36% decrease at 50 μg) and chlorocholine chloride (34%, 100 μg) showed the highest inhibitory effects. It was concluded that negative phytohormonal effects on native proteolytic activity may slow down organic matter decomposition rates and hence complicate plant nutrition. The study enhances the understanding of rhizosphere exudate effects on soil microbial activity and soil nitrogen cycle.

Problems of Managing Potato Plant Growth Under Micropropagation for Primary Seeds

This study shows the possibility of controlling the growth of potato microplants when adding the Murashige-Skoog (MS) nutrient medium chlorocholine chloride (CCC) to the composition at a concentration of 0.05-0.25 mg ⋅ L −1. Varietal specificity of the reaction of potato plants to the preparation was revealed. At optimal concentrations of CCC, plants with a stem length of 7-10 cm in 250 ml flasks were grown from single-node microcuttings for 1.5 months. Microplants were removed from the flasks using 20 cm scissors and unsterilized tweezers. The roots were shortened to 2-3 mm and the basal part of the stems was treated with a chalk-based paste containing 0.04% indolylbutyric acid (IBA). Plants were planted on 36 mm diameter Jiffy 7 peat pellets directly in the laboratory. The trays with the material were transferred to the greenhouse at the end of April at a temperature of 20-25 °C and placed in the conditions of the upper fine irrigation. After 3-4 days, mass root formation began in the plants, and another week later the seedlings were ready for use. By then the height of the plants was 10-15 cm, and the roots were clearly visible on the surface of the peat pellets. Planting these seedlings in a technological greenhouse to obtain minitubers was convenient and inexpensive. Keywords: potato, microcuttings, microtubers, minitubers, chlorocholine chloride, peat pellets

Induction of tolerance by chlorocholine chloride in Sequoia sempervirens seedlings under natural cooling and drought

Two-years-old Sequoia sempervirens seedlings were foliar sprayed once and twice with chlorocholine chloride (CCC) at 0, 100, 500, 1 000, 1 500 and 2 000 mg·l^–1. The purpose was to investigate the effect of CCC on the growth and photosynthetic activity of S. sempervirens seedlings under natural cooling and drought in autumn and winter. The findings showed that the increments of plant height and crown diameter were significantly decreased with the increase of chlorocholine chloride concentration, and the increment of root collar diameter, net photosynthetic rate, actual photochemical quantum yield and photosynthetic electron transport rate showed the trend of increasing first and then decreasing, and reached the maximum at concentrations of 1 000~2 000 mg·l^–1. There was not a significant difference between two applications and single application. It suggests that 1 000~2 000 mg·l^–1 chlorocholine chloride can protect the photosynthetic activity of S. sempervirens seedlings and alleviate the stress induced by low temperatures and drought in autumn and winter.

Proteolytic Activity in Meadow Soil after the Application of Phytohormones

Phytohormones, similar to soil enzymes, are synthesized and secreted into the soil environment by fungi and microorganisms. Phytohormones are involved in regulating microbial community activity in the rhizosphere. This paper examines how auxins, cytokinins, ethephon and chlorocholine chloride affect the activity of native soil proteases in the organo-mineral horizon of an alpine meadow. In the meadow habitat, native soil proteases were inhibited by auxins whereas the effect of cytokinins on these enzymes was not statistically significant. A similar inhibitory effect on the activity of proteases was shown for ethephon and chlorocholine chloride, both of which also inhibited the activity of native soil proteases in the alpine meadow soil. Overall, the inhibitory effect of phytohormones on the activity of native protease activity may affect plant nutrition by retarding the nitrogen cycle in the soil. This work contributes to our understanding of the influence of substances produced by the rhizosphere that can actively participate in the activity of soil microorganisms and consequently influence the soil nitrogen cycle.

Alteration in the Native Proteolytic Activity in the Forest Soil after the Application of Phytohormones

Soil proteases are involved in the transformation of organic matter and thus influence the nutrient turnover in the ecosystem. Phytohormones, similarly to proteases, are synthesized and secreted into the soil by fungi and microorganisms and regulating their activity in the rhizosphere. The aim of our work was to find out how the presence of auxins, cytokinins, ethephone and chlorocholine chloride affects the activity of native soil proteases at the spruce tree stand. Auxins stimulated the native proteolytic activity in the spruce tree stand. Synthetic auxins most stimulated the activity of 2-naphthoxyacetic acid and the naturally occurring auxins of indole-3-acetic acid in the organic horizon of the spruce forest. Cytokinins, ethephone and chlorocholine chloride inhibited the activity of native soil proteases in the spruce tree stand. The highest inhibitory effect was found in ethephone and chlorocholine chloride. Overall, the negative effect of phytohormones on the activity of the native proteolytic activity may slow down the decomposition of organic matter and thus make plant nutrition more difficult. The outcomes of our work assist with understanding of the effect of substances produced by the rhizosphere on the activity of soil microorganisms and the soil nitrogen cycle.