Alkaline salt impairs germination recovery more severely than neutral salt in the euhalophyte Suaeda salsa.

Abstract

Introduction: Soil salinization and alkalization increasingly threaten global ecosystem stability, necessitating a clearer understanding of how dominant halophytes respond to complex salt stresses.

Methods: This study examined the differential effects of neutral and alkaline salt stresses on seed germination and early seedling growth of Suaeda salsa, a dominant halophyte in the Yellow River Delta. A two-factor factorial experiment was conducted using three salt types (NaCl, KCl, NaHCO₃) across six concentration gradients (0-500 mmol L^-1). A two-stage germination trial, comprising an initial stress phase and a post-stress recovery phase, assessed root and shoot growth, fresh mass accumulation, water potential, and germination ratios.

Results: Salt concentration primarily determined germination traits. At comparable molar concentrations, alkaline salt (NaHCO₃) exerted significantly stronger inhibition on growth than the neutral salts (NaCl, KCl). Low-concentration NaCl promoted fresh mass accumulation and sustained shoot elongation through efficient osmotic adjustment, whereas alkaline stress severely impaired this capacity, inducing acute physiological drought. The secondary germination trial revealed an "enforced dormancy" strategy: the effects of neutral salt stress were largely reversible, with markedly enhanced germination upon stress relief, whereas alkaline salt stress reduced recovery potential, fundamentally compromising recovery potential.

Discussion: Neutral and alkaline components must be distinguished when evaluating soil degradation. Future ecological restoration in the Yellow River Delta should prioritize amelioration of high-pH alkaline conditions to ensure natural regeneration of halophyte communities.