THE INFLUENCE OF PHOSPHORUS AVAILABILITY, SCION, AND ROOTSTOCK ON GRAPEVINE SHOOT GROWTH, LEAF-AREA, AND PETIOLE PHOSPHORUS CONCENTRATION

Cabernet Sauvignon (CS) and Chenin blanc (Cb) scions on Freedom, AxR#1 , St. George, and 110R rootstocks were grown under conditions of suffi cient (+P) and deficient (-P) soil phosphorous availability. Shoot len gth, shoot dry weight, leaf area, and petiole P concentration were low er for -P compared to +P vines. Cb vines had larger leaves and more le af area than CS vines and the leaf area of Cb vines was less inhibited by exposure to -P than was CS vines. Vines on Freedom had longer shoo ts, greater shoot biomass, and greater leaf area than vines on other r ootstocks regardless of P availability. Under +P vines on St. George p roduced less shoot dry weight than vines on Freedom, but more than vin es on 110R. However, the shoot dry weight and leaf area of vines on St . George was greatly inhibited by -P and vines on St. George appeared to not use P efficiently for growth under these conditions. Vines on 1 10R produced the least amount of shoot growth and leaf area among the rootstocks under +P, but were also the least inhibited by -P condition s. The shoot dry weight and leaf area of vines on AxR#1 was intermedia te between vines on Freedom and vines on St. George and 110R, and were inhibited by -P slightly less than St. George. Freedom and 110R are m ore suitable for low P soils than St. George and AxR#1.