Enhancement of Physio-Biochemical Attributes and Seed Yield of Sunflower Through Integrated Application of Silicon and Mycorrhizal Fungi Under Salt Stress.

Abstract

Salinity is a predominant abiotic stressor that severely impairs agricultural productivity by disrupting plant physiological and biochemical processes. The strategic application of silicon (Si) fertilizer in conjunction with arbuscular mycorrhizal fungi (AMF) has emerged as a promising approach to alleviate the detrimental impacts of salinity stress in sunflower. The present study was conducted to assess the synergistic effects of monosilicic acid and AMF inoculation on the growth performance, physiological attributes, and seed yield of sunflower under varying levels of salt stress. A factorial experiment was arranged in a completely randomized design (CRD) with three replicates, comprising three factors: (1) four monosilicic acid application rates (0 [Si0], 150 [Si150], 300 [Si300], and 450 [Si450] kg ha⁻1), (2) four irrigation water salinity levels (0.54 [control], 4, 8, and 12 dS m⁻1), and (3) two AMF inoculation treatments (absence [–AMF] and presence [+ AMF]). Salinity stress significantly reduced all measured growth indices, physiological traits, and seed yield of sunflower but Si supplementation notably enhanced physio-biochemical traits and stress tolerance index. It has been reported that, Si-treated plants improved leaf relative water content by 45%, chlorophyll content (SPAD value) by 17%, and membrane stability index by 60%, along with a 15% reduction in electrolyte leakage, relative to untreated controls at 12 dS m⁻1 salinity level. Moreover, the highest accumulation of proline, was recorded in plants treated with Si450, with increases of 19% and 28% observed in AMF-inoculated and non-inoculated plants, respectively, compared to the non-saline control. AMF inoculation significantly enhanced reproductive output, with increases of 23% in capitulum (head) weight and 41% in seed number per plant compared to non-inoculated counterparts. Under high salinity (12 dS m⁻1), Si450 treatment led to a substantial increase in seed yield by 56% in + AMF plants and 50% in –AMF plants relative to the Si0 treatment. Collectively, the findings suggest that the integrated application of Si and AMF markedly augments morpho-physiological performance and seed yield of sunflower through mitigating the adverse effects of salt-induced stress.