# Biphasic Salt Effects on Lycium ruthenicum Germination and Growth Linked to Carbon Fixation and Photosynthesis Gene Expression

## TL;DR

This study explores how salt affects the germination and growth of Lycium ruthenicum, revealing how low salt levels promote growth while high levels inhibit it through changes in photosynthesis and gene expression.

## Contribution

The study identifies specific metabolic and gene expression mechanisms underlying biphasic salt responses in Lycium ruthenicum.

## Key findings

- Low NaCl concentrations promote germination by enhancing photosynthesis and maintaining cellular integrity.
- High salt levels disrupt photosynthesis and cause oxidative damage, inhibiting germination and root growth.
- Salt stress modulates carbon fixation pathways via RPIA and RuBisCO gene upregulation.

## Abstract

Since the onset of industrialization, the safety of arable land has become a pressing global concern, with soil salinization emerging as a critical threat to agricultural productivity and food security. To address this challenge, the cultivation of economically valuable salt-tolerant plants has been proposed as a viable strategy. In the study, we investigated the physiological and molecular responses of Lycium ruthenicum Murr. to varying NaCl concentrations. Results revealed a concentration-dependent dual effect: low NaCl levels significantly promoted seed germination, while high concentrations exerted strong inhibitory effects. To elucidate the mechanisms underlying these divergent responses, a combined analysis of metabolomics and transcriptomics was applied to identify key metabolic pathways and genes. Notably, salt stress enhanced photosynthetic efficiency through coordinated modulation of ribulose 5-phosphate and erythrose-4-phosphate levels, coupled with the upregulation of critical genes encoding RPIA (Ribose 5-phosphate isomerase A) and RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase). Under low salt stress, L. ruthenicum maintained intact cellular membrane structures and minimized oxidative damage, thereby supporting germination and early growth. In contrast, high salinity severely disrupted PS I (Photosynthesis system I) functionality, blocking energy flow into this pathway while simultaneously inducing membrane lipid peroxidation and triggering pronounced cellular degradation. This ultimately suppressed seed germination rates and impaired root elongation. These findings suggested a mechanistic framework for understanding L. ruthenicum adaptation under salt stress and pointed out a new way for breeding salt-tolerant crops and understanding the mechanism.