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 m(2) m(-2), the quantum saturated rate of A(c) (A(sat)) increased with increasing vine leaf area, from 29.0 - 37.8 mu mol 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 m(2) 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.