COMPARISON OF LEAF MINERAL CONTENT, CARBON ASSIMILATION AND STEM WATER POTENTIAL OF TWO APRICOT (PRUNUS ARMENIACA) CULTIVARS GRAFTED ON 'CITATION' AND 'MARIANNA 2624' ROOTSTOCKS
'Citation' (peach x plum) has been suggested to be a size-controlling rootstock for apricot that could allow denser planting and achievement of full production in the orchard's early life compared with standard rootstocks. In California, growers have observed that apricot trees grafted on 'Citation' often show yellowish foliage and are thought to require more frequent irrigation. To investigate this phenomenon, leaf photosynthetic rate, stem water potential, and leaf content of N, P, K, Zn, and Fe were measured in late summer on 'Royal/Blenheim' and 'Patterson' apricot cultivars grafted on 'Citation' and on 'Marianna 2624' rootstocks. Orchard management was consistent with standard practice. Leaf N and Zn contents were significantly lower in the trees grafted on 'Citation'. There was also a significant difference in N and Zn between the two cultivars; however, this difference disappeared when expressing the mineral content in mg.dm-2 of leaf area. Leaf P content was lower on 'Patterson' leaves, but there was no rootstock effect. Leaf photosynthesis was measured on September 23 and 29 between 10:30 and 11: 30 a.m. Trees on 'Citation' had significantly lower assimilation rates than those on 'Marianna 2624'. Differences in leaf photosynthesis were associated with the lower leaf N and Zn contents. 'Citation' had higher (less negative) stem water potential than trees on 'Marianna 2624' when measured at midday on the same day as gas exchange. 'Citation' rootstock may have reduced N and Zn uptake capacity and, as a consequence, may require more careful fertilizer management than 'Marianna 2624'.
Rosati, A., DeJong, T.M. and Southwick, S.M. (1997). COMPARISON OF LEAF MINERAL CONTENT, CARBON ASSIMILATION AND STEM WATER POTENTIAL OF TWO APRICOT (PRUNUS ARMENIACA) CULTIVARS GRAFTED ON 'CITATION' AND 'MARIANNA 2624' ROOTSTOCKS. Acta Hortic. 451, 263-268
Mineral nutrition, photosynthesis, stem water potential nitrogen