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EXPLORING THE HIDDEN THREAT OF GASEOUS POLLUTANTS USING RICE (ORYZA SATIVA L.) PLANTS IN PAKISTAN

A. WAHID¹ SHEIKH SAEED AHMAD²*, ZAHID ALI BUTT³ AND MAQSOOD AHMAD⁴

Abstract: Three rice (Oryza sativa L.) varieties (Basmati-Pak, Basmati-370 and IRRI-9) of Pakistan were grown for their entire life cycle in open top field chambers to investigate the impacts of ambient ozone (O₃), nitrogen dioxide (NO₂), and sulphur dioxide (SO₂) on the biomass, growth physiology, and yield. The treatments were charcoal filtered air (FA), unfiltered air (UFA) and ambient air (AA). O_3, NO_2, and SO₂ concentrations recorded at the experimental site were 75, 29 and 18 ppb as 8 h daily mean, respectively. Microclimate conditions inside and outside the chamber environment remained virtually similar. All the rice cultivars showed severe depression in biomass (20-30%) due to reductions in number of tillers (20-27%) and leaves per plant (21-29%) during vegetative growth phase with maximum reductions seen in both Basmati-370 and IRRI-9 in UFA treatments compared with FA. These reductions were primarily due to decreased transpiration rate (10-20%), stomatal conductance (12-23%), net photosynthetic rate (9-22%) and photosynthetic efficiency (6-12%) of plants in UFA. Yield losses in total seed weight per plant in UFA were more or less similar in IRRI-9 (37%) and Basmati-370 (36%), followed by lower reduction in cv. Basmati-Pak (29%). Reductions in number of panicles per plant (18-25%), filled seeds per panicles (8-11%), seeds weight per panicle (13-17%) and 1000-seeds weight (5-8%) in UFA contributed significantly towards greater yield depression. Percent seed sterility was also higher in UFA and AA treatment plants. Starch contents of seeds in UFA were reduced by 14%, 19% and 21% in Basmati-Pak, Basmati-370 and IRRI-9, respectively when compared to FA control. 

¹Department of Environmental Sciences, BZ University, Multan, Pakistan

²Department of Environmental Sciences, Fatima Jinnah Women University, Rawalpindi, Pakistan

³Department of Botany, GC University, Lahore, Pakistan

⁴Environment Protection Department, Government of the Punjab, Pakistan

*Corresponding address E-mail: drsaeed@fjwu.edu.pk; Tel: 00 92 321 5167726