Biomedical Engineering Reference
In-Depth Information
agricultural needs. Plant hormones are low molecular organic substances that are produced by
plants and possess regulating functions. Low concentrations (lower than 10
-11
М) of plant
hormones are active, with plant hormones causing various physiological and morphological
changes in the cells and systems of the organism which are sensitive to their influence.
In 1970 first reports of extracting lipid fraction from the pollen of rapeseed and alder
appeared; the extracted fraction possessed marked growth-regulating abilities. Active
components of this fraction were called brassinosteroids. Treatment of bean germinants with
brassinosteroids proved to increase the seed yielding capacity by 40%. Molecular structure of
the active component of new plant hormone group was defined in 1979. Brassinolide proved
to be this active component.
Brassinolide and its brassinosteriod analogues differ from other steroids due to lactone B
cycle unique to their structure. By now it has been determined that brassinosteroids act as
hormones increasing yield of the overwhelming majority of crops: rice, wheat, beans, corn,
being effective exclusively in the small (10-40 mg/ga) doses. Brassionosteriods improve plant
resistance to ambient adverse conditions: low temperatures, salinization, aridness, cold winds,
toxic chemicals etc. Discovered favourable effects of this steroid group are supposed to stem
from the ability to adjust the level of corresponding plant hormones in the organism of the
plant according to the stress [1].
The structure of brassinolide plant steroid was defined employing spectral methods and
X-ray crystallographic analysis. As per the results brassinolide plant steroid belongs to the
class of steroids and has a unique lactone B cycle structure, characterized by trans-AB-
articulation with 22R lateral chain, 23K diol groups as well as α
-
cis-diol group in A cycle.
The length of molecule is up to 6 nanometers, and its width is up to 1 nanometer. Molecules
of this size can easily penetrate any capillary and biological pores.
2.
B
RIEF OF
P
REVIOUS
W
ORK
The structure of sterane was formed on the early stages of natural selection of the
organisms. In the steroid aspect this structure is a “comfortable” bioorganic frame for
arranging different functional groups and radicals. Definite combination and topography of
these groups and radicals determines the formation of a great number of compounds with
various, especially, hormone activity of different types. As per their structure brassinosteroids
are close to steroid hormones of animals, they have specific influence on the cell membrane
permeability, regulating the inflow of definite class of substances, i.e. they increase
permeability for some substances and prevent others from penetrating. The second
mechanism of influence is specific impact on the activity of definite enzymes (biocatalysts,
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