# Physiological Responses of Grapevine Leaves to High Temperature at Different Senescence Periods

## TL;DR

This study explores how grapevine leaves respond to high temperatures at different stages of aging, revealing that younger leaves are more resilient but still suffer lasting damage.

## Contribution

The study provides new insights into the physiological and photosynthetic responses of grapevine leaves to heat stress across senescence stages.

## Key findings

- Young leaves maintain higher chlorophyll content but are prone to wilting, while older leaves show faster functional decline.
- High temperature impairs PSII function, as indicated by changes in chlorophyll fluorescence parameters like Fv/Fm and PIabs.
- Antioxidant enzyme activities and MDA levels fluctuate with leaf age and heat exposure, correlating with photosynthetic performance.

## Abstract

Leaf senescence is a precisely regulated developmental process that is critical for grapevine growth and yield, which is easily influenced by environmental factors. High temperature is a major factor that accelerates senescence rapidly, adversely affects photosynthetic performance, severely hindering fruit nutrient metabolism and growth. This study investigated chlorophyll fluorescence and physiological traits in grape (Vitis vinifera L.) leaves at different senescence stages under natural high-temperature conditions in Turpan. Measurements included chlorophyll content, MDA levels, antioxidant enzyme activities, and chlorophyll fluorescence parameters. The results showed that (1) young leaves exhibited higher and more sustained chlorophyll content but were prone to wilting, whereas older leaves showed accelerated chlorosis and functional decline; (2) high temperature severely impaired PSII function, inhibiting electron transport and photochemical efficiency, reflected in increased ABS/RC, TRo/RCC, and DIo/RC, and decreased Fv/Fm, Fv/Fo, and PIabs; (3) POD, SOD, CAT and MDA levels initially increased then decreased, correlating with photosynthetic changes and leaf age; and (4) young leaves maintained stronger photosynthetic capability and physiological resilience than older ones. Although partial recovery occurred after temperature reduction, photosynthetic and antioxidant activities did not fully revert. This suggests persistent heat-induced functional decline and accelerated senescence, providing insights for understanding heat-induced leaf senescence and developing strategies for cultivating grapevines.