Damage to Photosynthesis During Chilling and Freezing, and its Significance to the Photosynthetic Productivity of Field Crops

Abstract

Exposure of Z. mays, and other chilling sensitive plants, to high light during chilling (0 – 12°C) results in photo inhibition of photosynthesis (1–4). This inhibition is manifest as decreased CO₂ uptake rates at both light saturation (Asat) and under light limiting conditions — expressed as change in the maximum quantum yield (∅) (1,2). This inhibition is not readily reversible and may persist for several hours following return to non-chilling temperatures. In S. England, i.e. near the northern limit of Z. mays cultivation in Europe, chilling dependent photo inhibition of photosynthesis is frequently observed in May and June. Exposure of the young crop to a dawn temperature of 5°C coupled with clear sky conditions may result in a 50% reduction in ∅. If this is followed by a period of dull weather, recovery occurs within 3–4 days in the field (5). Z. mays might be viewed as exceptional. It is a crop of tropical origin which would be expected to be particularly susceptible to low temperature stress in N.W. Europe. Many of the major arable crops of N.W. Europe and other cool temperate climate zones are winter annuals which maintain a green leaf canopy throughout the winter and spring.