Phytohormone activity

Particularly rich in B. are pollens (for Brassica napus ca. 100 xg/kg). B., especially brassinolide and 24-epibrassinolide, have unusually high phytohormonal activity. B. effect a general promotion of growth in plants (e. g., in roots), stimulate photosynthesis and protein biosynthesis, modulate the mode of action of other phytohormones, and delay senescence processes. B. exhibit antiecdysteroid effects on insects. For practical uses of B. the so-called anti-stress action on plants is of major interest and has been detected in field experiments under unfavorable cultivation conditions (e.g., drought, cold, nutrient deficiency, pest infestation). 

Phytohormones, Phytotoxicity, Plant Growth Regulatory Activities... 

The biosynthesis of brassinosteroids has been investigated by in vivo feeding of plant cell cultures, in addition to the analysis of native brassinosteroid-pattems in diverse plant species. The proposed pathway (Fig. (1)) leads from unpolar sterol precursors to the polyhydroxylated phytohormone brassinolide, that is known to exhibit the highest biological activity. 

In order to study how a silatrane group which is present in phytohormones influences their activity we have investigated the action of silatranylmethyl esters of 2-methyl-phenoxyacetic, 4-chlorophenoxyacetic and 3-indolylacetic acids on the suspended cul-... 

The auxin activities of the above phytohormones as well as their silatranylmethyl esters are listed in Tables 26—28. 

OPDA was shown to promote tendril coiling response in Bryonia914 This compound was also shown to induce stomatal opening.915 The stomatal opening activity of OPDA is higher than that of other phytohormones that induce stomatal opening. 

After these detailed remarks about anti-gibberellins and their mode of action, it should be emphasized that the action of not all bioregulatory active substances can be assigned so precisely to an interaction with a specific phytohormone. This partially applies to daminozide (succinic acid 2,2-dimethylhydrazide), which is frequently classified as a retardant (7). 

Reference phytohormones Compounds with homologous or synergistic activity Compounds with an antagonistic activity or inhibitors of biosynthesis... 

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