Phytotoxic Effects of So2 on Crop Plants --Abiotic Stress and Reducing Sugars

Abstract

Effect of different SO₂ concentrations  on the reducing sugar content in the leaves of three economically important plant species, viz.,  Solanum esculentum (= Lycopersicon  esculentum )[Tomato], Vigna  radiata (Mung bean) and Zea  mays (Maize) was studied . Controlled fumigation experiments were carried out using three different treatments of SO₂ : T-1 = 0.05 ppm(134.0µg m^-3 SO₂)  [x 4h], T-2 = 0.1 ppm(268.0 µg m^-3 SO₂)  [x 2h] and T-3 = 0.2 ppm(536.0 µg m^-3 SO₂)  [x 1h] for 60 days. In Maize, the exposure period was extended to 75 days.  All the three plant species recorded an increase in sugar content following SO₂ exposure. Maximum increase in reducing sugar content was observed in S.esculentum, followed by V.radiata and Z.mays . Changes in reducing sugar content seems to point towards a shift in the energy budget in order to make energy readily available for repair/replacement of tissue damaged by SO₂  toxicity. Reducing sugar content can be used as a reliable indicator of the metabolic stress state of plants in the absence of any visible injury symptoms.