Plant-growth promoters, brassinosteroids

Mandava, N.B. (1988). Plant growth-promoting brassinosteroids. Ann. Rev. Plant Physiol, and Plant Mol. Biol. 39, 23-52. 

Mandava NB (1988) Plant growth-promoting brassinosteroids. Annu Rev Plant Physiol Plant Mol Biol 39 23-52... 

The original discovery of brassinolide, a natural plant-growth promoter extracted from bee-collected pollen, was made at the USDA Agricultural Research Center in Beltsville, Maryland. Although the USDA terminated brassinosteroid research, others around the world have carried on the work. This volume addresses the history, biochemistry, physiology, practical applications, production, synthesis, and entomological effects of these compounds. 

Brassinolide is known as the most potent compound for inducing plant growth promoting activity in various bioassay systems. Many researchers have attempted to demonstrate brassinosteroid application for agricultural use. However, test results have been disappointing in many cases under field conditions. Here, we discuss the capability and problems surrounding the potential practical uses of brassinosteroids. 

Brassinosteroids are ubiquitous in nature. Brassinolide was first isolated from the pollen of rape (Brassica napus L.) plant and has plant-growth-promoting activity on various plants. Following the brassinolide discovery, other (about 20) brassinosteroids including brassinolide were found mostly from various higher plants. 

The first synthesis of brassinolide (30) was achieved by Fung and Siddall in 1980,62 and also by Ikekawa and coworkers in the same year.63 Since then, many plant-growth promoters related to 30 with steroidal structures have been isolated from plants (Figure 2.21). They are called brassinosteroids. The early phase of our synthetic works on brassinosteroids has been reviewed.64... 

The amounts of homodolicholide (32)75 and homodolichosterone (35)76 isolated from Dolichos lablab were only 12 pg and 20 pg, respectively. It was therefore necessary to synthesize them in substantial amounts so as to evaluate their plant-growth-promoting activity. We synthesized these two brassinosteroids, as shown in Figure 2.25.68... 

The role of steroids as mammalian hormones has been known since 1930, and steroidal hormones have also been found in insects and fungi. Plants can biosynthesize a large variety of steroids, but it was not known until 1979 that steroids with plant growth-promoting activity were discovered. In that year. Grove et al. [1] reported the discovery of a new steroidal lactone called brassinolide from the pollen of Brassica napus L. To date, more than 70 structurally and functionally related steroids have been isolated from plant materials [2]. These compounds have been identified as members of a new group of plant hormones -the brassinosteroids (BRs). 

Following the isolation of the first steroidal plant growth promoter, brassinolide from rape pollen (77), 24-methylenebrassinolide and castasterone were characterized (Fig. 6). Fractionation of cat-tail pollen (25 kg), monitored by the standard rice lamina joint bending assay, led to the fourth brassinosteroid typhassterol 1.7 mg from 25 kg of pollen (72). 

Brassinosteroids are steroidal plant hormones which promote plant growth. To date the presence of over sixty kinds of brassinosteroids has been verified from various plant sources and thirty one of them fully characterized. In this chapter, the distribution and structural characteristics of the naturally-occurring brassinosteroids are discussed. 

In 1970, Mitchell et al. (1) isolated from pollen of rape a lipoidal complex termed "brassins" that has growth-promoting effects on plants. The active compound was eventually identified as a steroid derivative, which was given the name brassinolide (2). In the same year, two highly physiologically active brassinosteroids (a generic term for all compounds structurally related to brassinolide), 225,235,245 (tri-epi)-brassinolide (further referred to as BR-1) and 22/ ,231 ,245 (epi)-brassinohde (BR-2) were synthesized (3, 4). Ever since various synthetic routes have been developed to synthesize BR and its isomers (see elsewhere in this volume). 

Brassinosteroids are a family of hormones found in plants in which they are potent growth-promoters (reviews I, 2). Ecdysteroids on the other hand are a group of hormones occurring in all phyla of protostomian animals. In arthropods they are involved in the control of growth, morphogenesis, and reproduction (reviews 3, 4). While brassinosteroids have been detected in plants only, ecdyster-... 

Physiological Responses. Brassinosteroids promote plant growth by promoting cell elongation and cell division. In the presence of other plant hormones, when tested in systems specifically designed for them, brassinosteroids show the following effects, which are reversible (7—10) ... 

We know that brassinolide and the other brassinosteroids are novel plant growth regulators that contribute either to crop yield increases or to promotion of crop quality. How do we successfully exploit them for their use in commercial applications to agricultural productivity ... 

Brassinosteroids are growth-promoting plant growth regulators. They are probably endogenous hormones [62]. The two main members of the family are brassinolide (7-1) and castasterone (7-2). Over 60 kinds of brassinolide have now been verified from various plant sources, and thirty one have been fully characterised [63]. 

Brassinosteroids a class of growth promoting steroids widely distributed in higher plants (pollen seeds, 1-1,000 ng/kg shoots, 100 ng/kg fruit leaves, 1-10 ng/kg) and which have also been found in lower plants, including cyanobacteria. The first B., named brassinolide (2a,3a,22(I ),23(i )-tetrahydroxy-24(S)-... 

Krizek DT, Mandava NB (1983) Influence of spectral quality on the growth response of intact bean plants to brassinosteroid, a growth-promoting steroidal lactone. II. Chlorophyll content and partitioning of assimilate. Physiol Plant 57 324-329 Kumar D, Wareing PF (1972) Factors controlling stolon development in the potato plant. New Phytol 71 639-648... 

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