Bioregulators protected the leaf anatomy and photosynthetic machinery under water deficit stress in chickpea (Cicer arietinum L.)

Water deficit is undoubtedly one of the most important environmental stresses limiting the productivity of chickpea around the world. Exogenous application of bioregulators has been found to be a novel technology for imparting stress tolerance in crop plants. This study evaluated the changes brought about by two bioregulators viz., thiourea (TU) and thidiazuron (TDZ) under water deficit stress in chickpea leaf anatomy, chloroplast ultrastructure and photosynthesis. The experiment was conducted using Pusa 362 (Desi type) chickpea variety. Imposed water deficit treatment decreased relative water content (RWC), membrane stability index (MSI) and photosynthetic rate (P_N). However, bioregulators application maintained higher RWC, MSI and P_N under water deficit stress. Under imposed water stress, compact palisade layers of the mesophyll tissue were disrupted and cell size of the mesophyll cells displayed drastic reduction. Chloroplast, under water stress, displayed a number of grana with lose type of thylakoid, large increase in osmiophillic granules, reduction in the amount of starch granules and overall disruption of the thylakoid membrane. Foliar application of bioregulators maintained the integrity of mesophyll tissue and chloroplast structure thereby protected the chickpea plants from the detrimental effects of water deficit stress.