The salt bladder is essential for Atriplex canescens in response to salinity by regulating the ion homeostasis and water balance

Abstract

Background and aims

Salt bladders are specialized epidermal structures on the external aerial surfaces of certain recretohalophyte species and are generally believed to be related to salt tolerance. However, recent conflicting findings in quinoa raised questions about their exact function. Our previous studies suggested that salt bladders likely contribute to the salinity adaptation of the halophyte Atriplex canescens, but further direct confirmation is required.

Methods

The morphology and regeneration of salt bladders on leaf surface were examined using scanning electron microscope. The contribution of salt bladders to the salt tolerance of A. canescens was assessed by gently removing them from the surfaces of leaves and stems.

Results

Salt bladders of A. canescens exhibited remarkable regenerative capacity, which was significantly enhanced under NaCl treatments. Removing salt bladders weakened the salt tolerance of A. canescens, as plants lacking salt bladders (Br) showed significant declines in growth and photosynthetic capacity compared to intact plants (NBr) under saline conditions. Br plants also accumulated higher levels of Na⁺ and Cl⁻ in stems and leaves while retaining more K⁺ in roots than NBr plants when exposed to NaCl. Furthermore, the absence of salt bladders significantly reduced leaf relative water content, leaf succulence, excised-leaf water loss rate, and the water potential difference from root to leaf under saline conditions.

Conclusions

This study provides direct evidence that salt bladders are essential for the salt tolerance of A. canescens by maintaining ion homeostasis and water balance, highlighting their critical role in enabling this species to thrive in saline environments.