Combined use of proline and microbes on yield attributes, photosynthetic efficiency, water relations, nutrient acquisition and antioxidative defense mechanisms of fennel plants under drought conditions.

Abstract

The aim of the study was the induction of water stress tolerance in the fennel (Foeniculum vulgare Mill.) by the combined proline (Pro) and bacterial strain BEB1 (BEB1) application as foliar spray. Arrangement of experiment was done in field as split-split plot in open natural environmental conditions. Deficit water supply significantly adversely affected the growth and yield of fennel plants. Foliar-applied different treatments significantly reduced the water stress adverse effects on the performance of fennel plants regarding growth and yield that found linked to improvement in water status of plants and better net photosynthetic activity of fennel plants in comparison to non-treated plants. Combined application of Pro and BEB1 better maintained the seed yield and growth of fennel plants found associated with reduced lipid peroxidation, improvement in antioxidative defence mechanism, maintenance of plant water relations through better osmotic adjustment by increased accumulation of different metabolites. The maintenance of better yield and biomass production of water-stressed fennel plants also found positively associated with increased uptake as well as translocation of mineral nutrients. The maximum increase (30, 35 and 36, 34%) in shoot and root fresh and dry biomasses respectively and a decrease (24.13, 23.01 and 25.75%) in LRMP, MDA and H₂O₂ respectively, was found in plants sprayed with 1%Pro + BEB1. An increase of 41.43% in seed yield was recorded in fennel plants sprayed with 1%Pro + BEB1. Combined foliar spray of Pro and BEB1 was found better to increase tolerance against water stress for better yield by improving physio-biochemical mechanisms than their individual applications.