Changes in lipid composition in response to salt stress and its possible interaction with intracellular Na+-K+ ratio in sunflower (Helianthus annuus L.)

Abstract

Present work attempts to correlate soil salinity, pH and electrical conductivity with Na+, K+ and Ca2+ uptake in field-grown salt-sensitive, semi-salt tolerant and salt-tolerant sunflower (Helianthus annuus L.) plants. Accompanying steep rise in soil salinity and electrical conductivity, salt sensitive sunflower plants exhibit root proliferation, reduced lateral root formation and early floral induction, reflecting plant’s ability to restructure root architecture and flowering under salt stress. Loss in storage lipids and downregulation of oleic and linoleic acid levels under salt stress are correlated with the massive accumulation of Na+ in the achenes of salt-sensitive sunflower plants. Long distance stress signaling in sunflower achenes is marked with accumulation/loss of novel fatty acids, such as hexanoic acid (6:0) and cis-vaccenic acid (18:1Δ11) in salt-sensitive plants and eicosanoic acid (20:0) in semi-salt tolerant plants, highlighting their possible roles in regulating plant growth under salt stress. Storage lipids, such as TAGs (triacylglycerols) of salt-tolerant variety show a 40 % decline in U/S ratio (ratio of unsaturated/saturated fatty acids) under salt stress. Semi-salt tolerant and salt-sensitive varieties display a 16 and 26 % decline in U/S ratio, respectively. Present findings, thus, provide new information on lipids as salt markers in oilseed plants.