Estimating the Bioenergetic Cost of a Developing Kiwifruit Berry and its Growth and Maintenance Respiration Components

Abstract

A response surface was developed by regression analysis to quantify the seasonal respiratory losses by a kiwifruit [Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson var. deliciosa cv. Hayward] berry growing in Fresno, CA. The equation of the surface was LNRESP = 1·622 + 0·0697 × TEMP −0·0472 × DAY + 0·000165 × DAYSQ, where LNRESP is the natural logarithm of the respiration rate (nmol CO2 g d. wt−1 s−1), TEMP is fruit temperature (°C), DAY is the number of days after flowering, and DAYSQ is the square of the number of days after flowering. Respiratory losses for a fruit with a final dry mass of 18·5 g were calculated to be 5·57 and 5·92 g glucose per fruit per season in 1985 and 1986, respectively. Maintenance respiration was estimated to be 2·84 and 3·19 g glucose per fruit per season for 1985 and 1986, respectively. The total calculated bioenergetic cost of kiwifruit berry growth and respiration was 25·25 and 25·60 g glucose per fruit per season for 1985 and 1986, respectively. Respiratory losses, expressed as a proportion of the total carbohydrate required for fruit growth, were significant (mean 22·6%). The cost of fruit growth was estimated to be very similar for two cooler sites (Davis and Watsonville) but estimates of maintenance respiration based on Fresno fruit respiration data were unrealistically low for the Watsonville site.