Brassinolide, a growth‐promoting steroidal lactone

Abstract

Brassinolide (BR), a naturally‐occurring steroidal lactone was compared with GA3 and kinetin for activity in a number of bioassays. BR was highly active in elongation bioassays employing the dwarf pea epicotyl and etiolated bean hypocotyl that are responsive to GA3 but not IAA (at 0.01 to 10 μM). The elongation of the cucumber hypocotyl elicited by BR and GA3 was reduced far more than that elicited by IAA, following removal of the cotyledons. BR, like GA3 also inhibited betacyanin accumulation in Amaranthus seedlings and prevented adventitious root initiation in hypocotyls of mung bean, dwarf bean and cucumber. Application of BR promoted rather than retarded senescence of Rumex leaves. While almost half as effective as kinetin in promoting expansion of cucumber cotyledons, BR was ineffective in cytokinin bioassays involving expansion of dwarf pea epicotyl hooks, dark synthesis of betacyanin in Amaranthus and retardation of Xanthium leaf disc senescence. Unlike the case with IAA, BR does not interact synergistically with GA3. BR has proven active in promoting stem elongation in plant bioassays responsive to either IAA or GA3, or to both phytohormones. This effect, coupled to its effect on adventitious root formation, qualifies BR as a unique plant growth substance.

Effect of Epibrassinolide on Pigment Content, Total Protein Amount and Peroxidase Activity in Excised Cucumber Cotyledons

“…treatment of tomato pericarp discs with brassinosteroids resulted in considerable decrease in total chlorophyll content (28). An incubation of segments cut from mature Rumex or Xanthium leaves for 4 d with Bl in the dark actually promoted chlorophyll loss as compared to the control group (14).…”

Presence of Estrogens and Estrogen Receptor-like Proteins in Solanum glaucophyllum

“…Various steroids derived from plant and animal sources have been shown to affect in vitro cell growth and tissue differentiation in algae and vascular plant systems (1,(5)(6)(7)(8). However, the mechanism of action of endogenously synthesized steroids in plant cells is still poorly understood.…”

Genetic evidence for an essential role of brassinosteroids in plant development

“…Brassinosteroids stimulate growth through enhanced cell divisions and cell elongation (Mandava, 1988;Marquardt and Adam, 1991). In several systems they act synergistically with auxins (Katsumi, 1985;Kim et aL, 1990;Yopp et aL, 1981) and additively with gibberellins (Katsumi, 1985;Mandava et aL, 1981). Further observed responses to brassinosteroid application include enhancement or retardation of root growth, unrolling of leaves, differentiation of xylem vessels, enhanced ethylene production, membrane hyperpolarization, increased ATPase activity, enhanced DNA, RNA and protein synthesis, stimulation of photosynthetic activity, and changes in the balance of other endogeneous phytohormones (Arteca et aL, 1988;Braun and Wild, 1984;Cerana et aL, 1983;Clouse and Zurek, 1991;Clouse et aL, 1993;Eun et aL, 1989;Henry et al, 1981;Iwasaki and Shibaoka, 1991;Kalinich et aL, 1985;Romani et aL, 1983;Schlagnhaufer et aL, 1984;Wada et al, 1985;Yopp et aL, 1981).…”