Potassium nitrate, Silicon dioxide and Salicylic Acid Mediation Increase Seedling Growth, Biochemical Characteristics and Antioxidant Enzymes Activities in Rice (Oryza sativa) FARO44 Under Water Deficit Conditions

Abstract

Application of potassium nitrate, silicon dioxide and salicylic acid to seed are approaches that
impart stress tolerance to germinating seeds and seedlings under stressful conditions. This
study evaluated the effects of synergistic osmopriming and hormonal priming with 2.5%
KNO3+3.5% SiO2, 3.5% SiO2+1 mM SA and 2.5% KNO3+1 mM SA on seed germination,
seedling growth, antioxidant enzymes, protein, proline and malondialdehyde contents in 3-
weeks old FARO44 rice seedlings under drought conditions induced by polyethylene glycol
(PEG6000). Germination experiments were laid in a completely randomised design (CRD)
with each treatment replicated five times. The results revealed that synergistic priming
significantly seedling growth, antioxidant enzymes catalase, ascorbate peroxidase and
superoxide dismutase activities in rice seedlings by 2 folds compared to unprimed seedlings
under drought. Synergistic effect of priming methods improved protein and proline contents in
rice seedlings while decreased the content of malondialdehyde. Osmopriming and hormonal
priming with 2.5% KNO3+3.5% SiO2, 3.5% SiO2+1 mM SA as well as 2.5% KNO3+1 mM SA
showed different responses, however, they were found to be efficient in increasing germination,
growth of seedling, antioxidant enzymes’ activities as well as biochemical characteristics in
rice seedlings grown under water deficit conditions. Enhanced activities of antioxidants,
proline content as well as low malondialdehyde content in rice seedlings correlate with
improved drought tolerance. Therefore, pre-soaking of FARO44 in 2.5% KNO3+3.5% SiO2,
3.5% SiO2+1 mM SA or 2.5% KNO3+1 mM SA is recommended for fast germination, seedling
growth and drought tolerance in arid regions.