LIGHT AND TEMPERATURE EFFECTS ON WHOLE-CANOPY NET CARBON DIOXIDE EXCHANGE RATES OF APPLE TREES

Effects of previous days’ light conditions, hours of exposure to sunlight, time of the day, temperature and/or vapor pressure deficit (VPD) on whole-canopy net CO₂ exchange rate (NCER) of cropping field-grown ‘Empire’ or potted ‘Gala’ apple (Malus domestica Borkh.)/M.9 trees were studied.
In most studies, simultaneous single-leaf NCER measurements were also taken.
Artificial shading to 24% full sun for two previous days or to 23% full sun until mid-morning did not affect the subsequent whole-canopy and single-leaf NCER diurnal pattern of ‘Empire’ trees.
Light response curves of ‘Empire’ trees showed higher dark respiration rate (16 vs. 7% of the maximum NCER) and higher light compensation point (84 vs. 32 μmolm^-2s^-1) for whole-canopy than for single leaves.
Whole-canopy NCER of ‘Gala’ trees was negatively related to increases in air temperature from 15 to 34°C and/or VPD from 7 to 30 gm^-3. Whole-canopy and single-leaf NCER of ‘Empire’ and ‘Gala’ trees decreased throughout the day in most cases.
Possible mechanisms for the observed patterns and suggestions on measuring whole-canopy NCER are discussed.

VI International Symposium on Integrated Canopy, Rootstock, Environmental Physiology in Orchard Systems

A.H.D. Francesconi, A.N. Lakso, S.S. Denning

photosynthesis, Malus domestica, temperature, light

https://doi.org/10.17660/ActaHortic.1997.451.33