Freezing stress is a major constraint on citrus production, often causing cellular damage, reduced photosynthetic efficiency, and yield losses. In this study, researchers evaluated how exogenous proline application influences citrus physiological and metabolic responses under freezing conditions. Results showed that proline-treated plants maintained higher photosynthetic performance and membrane stability compared with untreated plants exposed to cold stress.
Proline biostimulation was also associated with enhanced antioxidant activity, reducing the accumulation of reactive oxygen species typically induced by freezing temperatures. This strengthened antioxidant defense helped limit oxidative damage to plant tissues during stress events.
In addition, proline-treated citrus plants exhibited coordinated regulation of carbohydrate metabolism. Improved sugar accumulation and utilization supported energy balance and osmotic protection, further contributing to cold tolerance and post-freeze recovery.
Together, these coordinated responses highlight proline’s role as an effective biostimulant for improving citrus resilience to freezing stress. The findings suggest that proline-based treatments could be a practical management tool to mitigate cold injury in citrus-growing regions increasingly affected by unpredictable temperature extremes.
This research advances understanding of plant stress physiology and provides growers and industry professionals with new insights into biostimulant-driven strategies for enhancing citrus cold hardiness and sustainability.
Dr. Shahid is Assistant Professor of horticulture and fruit crops at the University of Florida Institute of Food and Agricultural Sciences. His lab focuses on research in stress tolerance and physiology of fruit crops, including cold hardy citrus, tree fruit, tree nuts, and small fruits.
The full article can be found on the Journal of the American Society for Horticultural Science electronic journal website at:
https://doi.org/10.21273/JASHS05536-25
Established in 1903, the American Society for Horticultural Science is recognized around the world as one of the most respected and influential professional societies for horticultural scientists. ASHS is committed to promoting and encouraging national and international interest in scientific research and education in all branches of horticulture.
Comprised of thousands of members worldwide, ASHS represents a broad cross-section of the horticultural community – scientists, educators, students, landscape and turf managers, government, extension agents and industry professionals. ASHS members focus on practices and problems in horticulture: breeding, propagation, production and management, harvesting, handling and storage, processing, marketing and use of horticultural plants and products. To learn more, visit ashs.org.
