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Pak. J. Bot., 47(SI): 161-170, 2015.

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SEED PRIMING WITH SALICYLIC ACID INDUCES TOLERANCE AGAINST CHROMIUM (VI) TOXICITY IN RICE (ORYZA SATIVA L.)

KAMRAN IQBAL SHINWARI¹, MEHMOOD JAN¹, GULMEENA SHAH¹, SEHRISH RIAZ KHATTAK¹, SHAFIQ UREHMAN², M.K. DAUD¹, REHAN NAEEM¹ AND MUHAMMAD JAMIL¹*

¹Department of Biotechnology & Genetic Engineering, Kohat University of Science & Technology, Kohat 26000, Pakistan

²Department of Botany, Kohat University of Science & Technology, Kohat 26000, Pakistan

^*Corresponding author’s e-mail: dr.jamil@kust.edu.pk

Abstract: Anthropogenic activities caused release of toxic heavy metals including chromium (Cr) in environment all over the world, which pollute agricultural lands leading to reduction in growth of crop plants. Plant growth regulators like salicylic acid (SA) control growth and development and seed priming treatments with SA have been proven beneficial for plant growth. Therefore, the present study was focused on the potential mediatory role of SA under Cr (VI) toxicity in rice. For priming, seeds of two rice varieties, namely, Basmati-385 (B-385) and Shaheen Basmati (SB) were soaked in 0 (hydroprimed), 0.25 and 0.50mM solution of SA for 24hrs at room temperature. SA and hydroprimed seeds were grown in petriplates and later transferred to trays containing Hoagland’s nutrient medium up to 24 days and then 0 (control), 25, 50  and 100µM Cr (VI) stress was applied for one week. Cr treatments resulted in reduction of physiological parameters like germination rate and percentage, seedling vigor and seedling dry biomass while priming with SA treatments showed protection against Cr. Biochemical analysis of rice leaves showed that Cr stress alleviated chlorophyll content, accelerated cell membrane damage, decreased content of Na⁺, K⁺ and Ca⁺² ions and also reduced the total nitrogen content but SA priming mitigated the negative effect on these parameters. Cr content was lowered in leaves of SA primed plants in comparison to non SA primed plants under the respective Cr concentrations. Chromium (VI) stress applied to SA unprimed plants elevated the levels of stress metabolites i.e. total soluble proteins, total soluble sugars, glycinebetaine and proline content while SA priming lowered the toxicity of Cr manifested by alleviation in level of different stress metabolites. The important role of SA priming in inducing tolerance against environmental stresses may be due to its ability in expressing defense related proteins, which may provide tolerance against Cr. It can be suggested from the results that SA seed priming enhances resistance in rice against Cr.

Key words: Seed Priming, Salicylic Acid, Chromium, Oryza sativa