WHOLE-PLANT PHOTOSYNTHESIS IN KIWIFRUIT VINES – TEMPORAL CHANGES ON DIURNAL AND SEASONAL SCALES

Temporal variation in measured photosynthesis (A_c) for kiwifruit vines has been described, on diurnal and seasonal scales.
Short-term measurements focused on light (A_c) response described with an asymptotic exponential expression, For vines with leaf area of ca 2.0 – 2.6 m² m^-2, the quantum saturated rate of A_c (A_sat) increasing vine leaf area, from 29.0 – 37.8 μmol CO₂ m^-2 s^-1. Longer-term measurements focused on the relationship between diel integrals of A_c (A_d,) and leaf area. A_d increased from -0.7 mol CO₂ m^-2 day^-1 soon after bud burst, to as high 1.4 mol CO₂ m^-2 day^-1 near the summer solstice.
A regression of A_sat against leaf area indicated that A_d did not peak until leaf area has exceeded ca 2.5 m² m^-2. Diel measurements of A_c have illustrated “mid-day decline”, consisting with feedback inhibition, where A_c early in the day has been relatively high.
Maintaining a high ambient CO₂ during the day can over-ride the mid-day decline suggesting that source : sink interactions may involved.

III International Symposium on Kiwifruit

J.G. Buwalda, A.J. Greaves

https://doi.org/10.17660/ActaHortic.1997.444.53