Physiological and biochemical responses of sugar beet (Beta vulgaris L) to ultraviolet-B radiation.

Parisa Rahimzadeh Karvansara,Seyed Mehdi Razavi

doi:10.7717/peerj.6790

Abstract

Ultraviolet radiation can cause many serious problems for all living organisms. With a growing population, the UV sensitivity of crop plants presents a particular problem. To evaluate the suitability of growing in areas under UV irradiance, the influence of different doses of UV-B (3.042, 6.084 and 9.126 kJm−2d−1) on the sugar beet (Beta vulgaris L) plants was studied. UV-B induced a significant decrease in growth displayed as reduced height and fresh and dry weight. This reduction is not dose dependent and was associated with diminishing photosynthetic O2 evolution, relative chlorophyll content, photosynthetic pigments and chlorophyll fluorescence. On the other hand, antioxidant enzyme activities, total protein content, compatible solutes, total free amino acids and total betalain content were increased under 9.126 kJm−2d−1 UV-B treatments, representing mechanisms by which the plants coped with the stress. The oxidative stress upon UV-B treatment was evident by increased malondialdehyde (MDA) content, however, hydrogen peroxide (H2O2) was not affected in UV-B exposed plants. Thus, the studied sugar beet variety BR1seems to be suitable particularly for areas with high doses of UV-B irradiation.

Highlights

Ultraviolet radiation (UV) with wavelengths between 10 nm and 400 nm constitutes about 10% of the total light output of the Sun
The fresh weight of plants treated with the highest dose of UV-B showed the greatest decrease in fresh weight, whereas the weights of plants treated with the lowest and middle doses were identical
While UV-B treatment affected the growth of the sugar beet, a three-fold difference in dose of UV-B irradiation had only a minor influence on the BR1 cultivar (Dataset S1, Dataset S2, Dataset S3)

Summary

Introduction

Ultraviolet radiation (UV) with wavelengths between 10 nm and 400 nm constitutes about 10% of the total light output of the Sun. Reductions in the ozone layer, such as those observed transiently in the 1990s, are connected with increased levels of UV-B, with consequences for human health (Ramanathan & Feng, 2009; Young, Claveau & Rossi, 2017). UV-B radiation can cause a number of malfunctions and growth inhibition in plants. Many plant processes such as photosynthesis, biomass allocation, dark respiration, transpiration, and growth are affected by UV radiation. This is a consequence of macromolecule damage by UV-B causing double helix DNA breaks, lipids peroxidation and protein degradation in exposed plants. Plants can induce defense reactions to UV radiation and may achieve some degree of tolerance (Rahimzadeh, HosseiniSarghein & Dilmaghani, 2011)

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