Plant growth regulating substances are involved in the
physiological and metabolic processes of plants and enable
them to cope with numerous environmental stresses. The
effect of exogenously applied brassinolide (BR) with various
concentrations (0.01, 0.1, and 1.0 mg L
-1) was studied on
morphological and physiological traits of
Leymus chinensis
(Trin.) Tzvelev under room and high temperatures in pots.
The experimental results revealed that high temperature
stress substantially perturbed growth, photosynthetic
pigments, and root activity of
L. chinensis; however, the
deleterious effects of high temperature were partially
ameliorated by the foliar application of BR. Compared
to room temperature, high temperature stress decreased
the plant height, leaf area, plant fresh and dry weight,
chlorophyll a and b content, chlorophyll a/b ratio as well
as root activity, while exacerbated the membrane damage
as indicated by enhanced production of malondialdehyde
(MDA). Accumulation of proline content, soluble protein
and sugar content in
L. chinensis improved by heat stress,
compared with normal temperature; application of BR
further improved their production thus aiding in the
attainment of tolerance against heat stress. Elevated levels
of antioxidant enzymes such as superoxide dismutase
(SOD), peroxidase (POD), catalase (CAT), ascorbate
peroxidase (APX), and glutathione reductase (GR) were
observed under heat stress compared to room temperature,
however, application of BR further proved beneficial in
this regard. Our results indicated that BR could improve
the growth and development of
L. chinensis by enhancing
the biosynthesis of photosynthetic pigments, osmolytes
and antioxidant enzymes system in plants under both room
and high temperature.
