# Hydrogel Systems in Plant Germplasm Cryopreservation: A Comprehensive Review

## TL;DR

This paper reviews how hydrogel systems can improve the cryopreservation of plant germplasm by protecting plant tissues during freezing and thawing.

## Contribution

The paper provides a comprehensive review of recent advances in hydrogel systems for plant cryopreservation and outlines design principles for future materials.

## Key findings

- Hydrogel systems reduce cryoinjury and improve post-thaw recovery in diverse plant explants.
- Recent hydrogel innovations include composite polysaccharides, protein matrices, and functionalized hybrids.
- Performance of hydrogels depends on their physicochemical properties and structural design.

## Abstract

Cryopreservation is a critical strategy for the long-term conservation of plant germplasm, particularly for clonally propagated crops, endangered species, and plants producing recalcitrant seeds. Hydrogel-based encapsulation systems can improve survival during ultra-low-temperature storage by providing mechanical protection, moderating dehydration, and regulating cryoprotectant uptake. Although calcium–alginate beads remain the traditional matrix for encapsulation–dehydration and encapsulation–vitrification, recent advances in biomaterials science have enabled the development of composite polysaccharide blends, protein-based matrices, synthetic polymer networks, macroporous cryogels, and functionalized hybrid hydrogels incorporating surfactants, antioxidants, or nanomaterials. These engineered systems provide improved control over water state, pore architecture, diffusion kinetics, and thermal behavior, thereby reducing cryoinjury and enhancing post-thaw recovery across diverse plant explants. This review synthesizes current knowledge on hydrogel platforms used in plant cryopreservation, with emphasis on how physicochemical properties influence dehydration dynamics, cryoprotectant transport, vitrification stability, and rewarming responses. Performance across major explant types is assessed, key limitations in existing materials and protocols are identified, and design principles for next-generation hydrogel systems are outlined. Future progress will depend on material standardization, integration with automated cryopreservation workflows, and the development of responsive hydrogel matrices capable of mitigating cryogenic stresses.