Ozone stress

Wheat yield in danger

By Biplab Das
Published: Saturday 04 July 2015

OZONE is harmful not only to human beings but also to plants. Modern bread wheat, Triticum aestivum, which is the staple diet of a majority of the world populace, is an ozone-sensitive crop.

Studies carried out between 1980 and 2007 show that ozone ranging between 30 and 200 parts per billion (PPB), decrease grain yield by 29 per cent in wheat. Studies also show ozone exposure affects tobacco and rice. But a detailed study on biochemical changes triggered by elevated near-surface ozone in ozone sensitive crops like wheat, is lacking.

A research team from India, Japan and Nepal found that ozone can harm wheat leaves by disrupting photosynthesis and the activity of vital proteins and genes.

Researchers used two wheat cultivars Sonalika and HUW 510 which are highly popular for their medium life span (120 days) and high yield. They exposed them to four different ozone concentrations—nearly no ozone, ambient ozone, ambient plus 10 ppb ozone and ambient plus 20 PPB ozone— one, in an enclosed chamber and the other in a natural environment, simulated at Banaras Hindu University (BHU), Varanasi. Both varieties were exposed to ozone for five hours a day, for 50 days through ozone generators.

Plants exposed to ozone showed rotten spots on leaves. After 10 days of exposure to ambient plus 20 PPB ozone, damaged leaves were found in both wheat varieties. After 50 days, no injury was found in plants not exposed to ozone.

Sonalika showed significantly better resistance. Total chlorophyll and carotenoids were significantly reduced under ozone stress in both wheat cultivars. After penetrating the stomata of the leaves, ozone reacted with its components and reduced major leaf proteins.

“Studies show that in the future, ozone will be a threat for wheat production, but differential responses among wheat varieties might help plant breeders to find out a suitable variety for an area experiencing higher concentrations of ozone,” said lead researcher Sashi Bhushan Agrawal.

The findings were published in the September issue of Journal of Proteome Research.

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