Abstract

Understanding how ice forms in plants is crucial to reducing crop losses amid increasing climate extremes. Unlike in animal tissues, the microscopic details of ice formation within plant cell walls remain poorly understood. Here, we combine plant biology experiments and molecular simulations to investigate the crosslinking of homogalacturonan (HG) pectin under different functionalisation states (deprotonated, protonated, methylesterified). We show that the degree and nature of HG crosslinking strongly affect cell wall porosity, as revealed by experiments supported by mathematical modelling. This porosity, in turn, governs the rate of ice propagation through plant tissue. Both cold acclimation and Ca²⁺ supplementation – which enhance HG crosslinking – improve frost resistance similarly. Simulations further indicate that while HG alone is a weak ice nucleator, ordered HG networks may promote ice formation. Conversely, excess hydration reverses the inhibitory effect of crosslinking due to swelling. Molecular dynamics results reveal that HG crosslinking controls pore size and restricts ice growth via the Gibbs–Thomson effect, providing a physical basis for freezing tolerance through cell wall remodelling. These findings highlight how plants regulate ice formation by tuning pectin architecture, suggesting new strategies for improving frost resistance in crops.