RELATIONSHIP OF PHOTOSYNTHESIS MEASUREMENTS TO FRUIT SOLUBLE SOLIDS AND SPECIFIC LEAF WEIGHT IN APPLE AND GRAPE WITH VARIOUS MEASURING TECHNIQUES

Photosynthesis, light (PAR) and transpiration were measured with an ADC portable infrared gas analyzer on apples and grapes. Measurements were taken on north and south sides of the rows, in the morning and afternoon, on sun and shade leaves, and with the leaf chamber in a horizontal position and in a natural leaf orientation position. Measurements were made on three cloudless days in August 1990 and 1991. Subsequently, fruit adjacent to sampled leaves were harvested and soluble solids determined. Sampled leaves were then harvested and leaf areas and dry weights measured. Correlation coefficients of variables were then subjected to analysis of variance to determine which techniques gave the best correlations. Grapes and apples responded differently. For grapes, soluble solids were most closely correlated to light and photosynthesis measurements when measured on south side shade leaves, while with apples, blush side soluble solids were best correlated with measurements on south side sun leaves in the afternoon. Specific leaf weight was best correlated to photosynthesis and light with grapes when measured on north side sun leaves and with apples when measured on the south side in the morning.