Influence of Rootstocks and Microsprinkler Fertigation on Photosynthesis of ‘Fuji’ Apple Trees

Abstract

Net photosynthesis (Pn) and transpiration (Tr) of shoot and spur leaves of ‘BC-2 Fuji’ apple trees ( Malus domesticaBorkh.) as influenced by five different rootstocks, B.9, M.9 NAKBT337, O.3, M.26 EMLA, M.7 EMLA and five different nutrition treatments consisting of 22.4 kg nitrogen (N)/ha (low N), 89.7 kg N/ha (medium N), 156.9 kg N/ha (high N), 89.7 kg N/ha plus 78.5 kg potassium (K)/ha (medium N + K), and 156.9 kg N/ha plus 78.5 kg K/ha (high N + K), applied through a microsprinkler system, were studied in 1998 and 1999. There was no interaction between rootstocks and fertigation treatments. Shoot leaves of trees on O.3 had significantly higher Pn than those on B.9 and M.7 EMLA rootstocks in August of 1998 and in July and August of 1999. Shoot leaves of trees on B.9 had 13% lower Pn than those on other rootstocks in June 1999. Rootstocks had little effect on the Pn of scion spur leaves. Shoot leaves of trees receiving low N had significantly lower Pn than those with medium N or high N on all sampling dates in 1998 and in June of 1999. Also, spur leaves on trees receiving low N had significantly lower Pn than those with high N on all sampling dates in 1998. Shoot leaves had significantly higher Pn than spur leaves with exception of July of 1999.