Investigation into the mechanisms of photosynthetic regulation and adaptation under salt stress in lavender

Salinity stress is a major threat to agricultural productivity and sustainability, often causing irreversible damage to photosynthesis. Lavender, a valuable aromatic plant, experiences growth impacts under salt stress. However, the regulatory mechanisms of photosynthesis related to its adaptation to salt stress remain unclear. In this study, lavender was exposed to 0, 100, 200, and 300 mM NaCl for 28 days. It was observed that lavender effectively maintained chlorophyll stability when salt concentrations were below 200 mM and stress duration was under 21 days. The most effective model for lavender under salt stress was identified as a right-angled hyperbolic modified model. Under moderate salt stress (100 mM, 200 mM), genes such as LaPSB28, LaPSBS, and LaPSBR contributed to PSII core stability, enhanced photosynthetic pigment levels, and sustained high electron transfer rates to improve salt-tolerance. Additionally, LaLHCB4-1 and LaPSAK-1 regulated stomatal size, thereby facilitating gas exchange and supporting the photosynthetic process. Conversely, under high salt stress (300 mM), LaPSBW-1, -2, and LaPSAB were found to reduce photosynthetic pigment levels and inhibit photosynthetic activity. However, genes such as LaCHLG-2, LaGLG-3, LaBAM1-1 and -3, and LaCHLP-3 aided in starch synthesis by increasing pigment content, thus promoting energy balance and enhancing salt tolerance. This regulation involved photosynthesis-antenna proteins and pathways related to starch, sucrose, and chlorophyll metabolism. These findings may support the cultivation of salt-tolerant lavender varieties and maximize saline soil usage.