ORIGINAL PAPER Heat-stress induced inhibition in growth and chlorosis in mungbean (Phaseolus aureus Roxb.) is partly mitigated by ascorbic acid application and is related to reduction in oxidative stress Sanjeev Kumar • Ramanpreet Kaur • Navneet Kaur • Kalpna Bhandhari • Neeru Kaushal • Kriti Gupta • T. S. Bains • Harsh Nayyar Received: 10 May 2010 / Revised: 17 February 2011 / Accepted: 23 March 2011 / Published online: 9 April 2011 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2011 Abstract The rising temperatures ( [ 35°C) are proving detrimental to summer-sown mungbean genotypes that experience inhibition of vegetative and reproductive growth. In the present study, the mungbean plants growing hydroponically at varying temperatures of 30/20°C (con- trol), 35/25, 40/30, and 45/35°C (as day/night 12 h/12 h) with (50 lM) or without ascorbic acid (ASC) were inves- tigated for effects on growth, membrane damage, chloro- phyll loss, leaf water status, components of oxidative stress, and antioxidants. The ASC-treated plants showed significant improvement in germination and seedling growth especially at 40/30 and 45/35°C. The damage to membranes, loss of water, decrease in cellular respiration, and chlorophyll were significantly prevented by ASC treatment to plants growing at these temperatures. The oxidative stress measured as malondialdehyde and hydro- gen peroxide content was observed to be significantly lower at high temperatures with ASC application. The activities of superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase increased at 40/30°C but decreased at 45/35°C in the absence of ASC while with its application, the activities of these enzymes were appreciably resorted. Among all the antioxidants, the endogenous ASC content decreased to the greatest extent at 45/35°C grown plants indicating its vital role in affecting the response of mungbean to heat stress. Exogenously applied ASC raised its endogenous content along with that of glutathione and proline at 45/35°C. The findings indi- cated that heat stress-induced inhibition in growth and chlorosis was associated with decrease in leaf water status and elevation of oxidative stress, which could partly be prevented by exogenous application of ASC. Its role in imparting protection against heat stress is discussed. Keywords Ascorbic acid Á High temperature Á Mungbean Á Oxidative stress Introduction Heat stress is one of the primary stresses limiting the performance of plants over the globe (Wahid et al. 2007). The rise in temperatures is drastically affecting the growth and production potential of crops, especially for those being grown in the tropical conditions (Hall 2001). The above-optimum temperatures can induce chlorosis, sun- burns on vegetative tissues, senescence and abscission of leaves, inhibition in the growth of roots and shoots, and finally substantial reduction in seed yield in various plant species (Giaveno and Ferrero 2003; Vollenweider and Gunhardt-Goerg 2005). Heat stress can cause several alterations at cellular and sub-cellular levels and the response of the plants depends upon the growth stage, intensity, and duration of the exposure to heat stress (Sung et al. 2003). The direct effects of heat stress include denaturation of proteins and enzymes (Kepova et al. 2005), damage to membranes (Liu and Huang 2000) while its indirect effects may include inacti- vation of enzymes present in the mitochondria and chloroplasts, impaired protein synthesis, degradation of Communicated by A. Kacperska-Lewak. S. Kumar Á R. Kaur Á N. Kaur Á K. Bhandhari Á N. Kaushal Á K. Gupta Á H. Nayyar (&) Department of Botany, Panjab University, Chandigarh 160 014, India e-mail: harshnayyar@hotmail.com T. S. Bains Department of Plant Breeding, P.A.U., Ludhiana 141001, India 123 Acta Physiol Plant (2011) 33:2091–2101 DOI 10.1007/s11738-011-0748-2