The plant growth regulator activity of one biostimulant and its impact on the heat tolerance of perennial ryegrass (Lolium perenne L.).

摘要

The objectives of this research were to determine if one biostimulant, Terra-Sorb Foliar (TS), which is sold as Macro-Sorb Foliar in the United States, exhibits hormonal activity and/or affects the heat tolerance of perennial ryegrass (Lolium perenne L.). Furthermore, to determine if plant responses elicited by TS are due to the nitrogen associated with the product in the form of amide groups, or from an unknown, organic component, which might have biological activity. In addition, repeat applications of TS prior to heat stress (pre-TS) were assessed compared to applications of TS at the onset of the stress (POST).;In vitro growth responses elicited by separated fractions of TS were investigated using two bioassays specific and sensitive to auxins and cytokinins. Results showed that TS promoted cell elongation in vitro using the Avena (oat) first internode segment straight growth auxin bioassay. A lipid soluble fraction of TS produced significantly more growth than both the water soluble fraction and a nitrogen control. TS did not elicit plant responses similar to cytokinins using the Raphanus (radish) cotyledon expansion bioassay or the Nictotania (tobacco) stem pith callus bioassay.;Subsequent experimentation revealed that the lipophilic fraction of TS elicited leaf bending similar to brassinolide using the rice lamina inclination bioassay, demonstrating that TS might contain a specific sterol compound, or derivative, which is biologically active in vitro.;Total polyphenol (antioxidant) concentration was measured as an indicator of plant stress. Polyphenol levels were significantly lower for pre-TS treated perennial ryegrass compared to controls at 36°C, but the effect of temperature was not significant. For any given response, treatment differences were not detected for plants maintained at 20°C, and only photochemical efficiency treatment differences were detected for plants growing at 28°C.;The overall conclusions generated from this thesis are that one biostimulant, Terra-Sorb Foliar (TS), elicited hormonal activity, including sterol growth responses in vitro and improved the heat tolerance of perennial ryegrass in a highly controlled environment (36°C), including responses which were significantly different from mineral nutrition treatments. Therefore it is possible, but not proven, that the biological activity exhibited by Foliar in vitro is also functioning in vivo leading to improved heat tolerance of perennial ryegrass. (Abstract shortened by UMI.).