Studies on epibrassinolide induced amelioration of high temperature stress in brassica juncea (L.) czern & coss
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Date
2010
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Publisher
CCSHAU
Abstract
The present investigations were undertaken to study the role of epibrassinolide (EBR) on seed
germination, seedling growth, 50% seedling mortality, relative water content, membrane stability, free
proline content, antioxidative enzymes and metabolites at seedling stage, while gaseous exchange and
yield attributes at terminal stage in field grown Brassica juncea plants.
When seedlings were grown at 25C, 30C or 35C, it was observed that 25C is optimum
temperature for germination and seedling growth. The germination, speed of germination and seedling
growth of Brassica juncea in general reduced when temperature was increased from 25C to 30C and
35C. Soaking seeds in EBR (10-6 M, 10-8 M or 10-10 M) for 2 hrs in general reduced germination,
seedling growth and delayed seedling mortality. Higher the concentration of EBR used, more was the
reduction in germination and seedling growth.
Acclimation at sublethal temperature (32C) and EBR pretreatments (10-8 M and 10-10 M )
for 24 hrs prior to high temperature stress (45C) were found to be effective in imparting thermo
protection at seedling stage, which is the crucial stage of plant establishment. These pretreatments
helped seedling to recover from heat stress by improved relative water content, reduced per cent injury
and increased free proline content. Increase in enzymatic activity of catalase, peroxidase, and also
reduction in MDA, H2O2 content conferred thermotolerance.
At flower cessation stage, compared to normal sown, in late sown crop the rate of
photosynthesis and seed yield decreased significantly whereas, rate of transpiration and stomatal
conductance increased. Rate of photosynthesis, transpiration and stomatal conductance increased in
plants sprayed with EBR at flower cessation stage. Lower concentration of EBR (10-10 M) was more
effective to bring consecutive improvement in gaseous exchange. EBR spray (10-10 M) increased the
seed yield (13.6%) and oil content (4.23%) as compared to control. Lower concentration of EBR (10-10
M) in general was more effective in imparting thermotolerance in B. juncea.
Description
Keywords
Planting, Sowing, Enzymes, Brassica juncea, Biological phenomena, Organic compounds, Germinability, Biological development, Yields, Developmental stages