Plant Science, 90 (1993) 179-185 179 Elsevier Scientific Publishers Ireland Ltd. Cell membrane stability and biochemical response of cultured cells of groundnut under polyethylene glycol-induced water stress B. Venkateswarlu and K. Ramesh* Division of Crop Sciences, Central Research Institute for Dryland Agriculture, Hyderabad 500 659 (India) (Received October 5th, 1992; revision received December 3rd, 1992; accepted February 1st, 1993) Cell membrane stability (CMS) in suspension cultures of two groundnut cultivars was studied under polyethylene glycol(PEG)- induced water stress. There was a negative relationship between PEG concentration in the medium and membrane stability measured as electrolyteleakage. The CMS values in the cell cultures correlated well with the whole plant tissue and permitted the differentiation of cultivars based on their known response to drought stress. The cell membrane stability was lower (more electrolyte leakage) when cells were grown in culture as compared to the intact plant tissue. Kadiri-3, the drought tolerant cultivar maintained higher CMS than JL-24, the drought susceptibleone. With increasing PEG levels the concentration of Potassium in cultured cells declined in both cultivars. However, Kadiri-3 maintained higher K values than JL-24 accompanied with greater cell membrane stability. Total soluble sugars also increased with increasing stress in both cultivars; the increase being higher in Kadiri-3. There was no significant change in the total free amino acids but proline accumulated markedly in both varieties. However, no relationship was found between proline levels and CMS. The results demonstrated that CMS test can also be used under in vitro conditions to differentiate the drought toler- ant and susceptible cultivars and the cellular K level has a positive relationship with membrane stability. Key words: cell membrane stability; groundnut; tissue culture; water stress Introduction Evaluation of cell membrane stability as a mea- sure of drought and heat tolerance, first introduc- ed by Sullivan [1] has been applied to a number of field crops [2-4]. This is based on the in vitro dessication of leaf tissue by a solution of polyethy- lene glycol (PEG) and the subsequent measure- ment of electrolyte leakage into the aqueous medium [3]. Sadalla et. al. [5] have applied this technique for field screening of wheat genotypes and successfully differentiated the heat tolerant and sensitive types. Premchandra et al. [4,6,7] have further characterised the relationship of a number Correspondence to." B. Venkateswarlu, Division of Crop Sciences, Central Research Institute for Dryland Agriculture, Hyderabad 500 659, India. *Present address: Dalmia Center for Biotechnology,Tirunagar, Madurai-6, India. 0168-9452/93/$06.00 © 1993 Elsevier Scientific Publishers Ireland Printed and Published in Ireland of physiological and nutritional parameters with the cell membrane stability in maize. With the availability of in vitro plant culture techniques, callus and suspension cultures of dif- ferent crops have been used for screening against stress factors [8,9]. In the present study we have at- tempted to apply the CMS test to the cultured cells of groundnut, simultaneously comparing with the response of intact leaf tissues. The relationship, if any, between the concentration of soluble sugars, free amino acids, proline and potassium has been worked out with CMS in two contrasting cultivars of groundnut. Materials and Methods Establishment of suspension cultures Two cultivars of groundnut viz., Kadiri-3 and JL-24 have been used in the present experiment. Ltd,