Boron Transport and Soluble Carbohydrate Concentrations in Olive

10 B application to leaves of various ages, there was significant 10 B export out of the treated leaves, and significant 10 B enrichment in nontreated adjacent organs, including inflorescences and fruit. Results demonstrated that B can be remobilized from leaves of various ages, and that foliar-applied B is phloem mobile in olive. Soluble carbohydrate analysis determined that mannitol and glucose are the predominant sugars in all organs analyzed and that the mannitol concentration in the leaves is adequate to account for all B transport. This is consistent with observations in other species, where the presence of mannitol is known to facilitate phloem B transport through formation of a mannitol-B complex. Previous reports have indicated that B application can alter carbohydrate metabolism. In the present study, foliar B application significantly suppressed glucose concentration in the leaf petioles of all ages and increased mannitol in petioles of the current-year-developed leaves. stages: during rapid inflorescence expansion (21 Apr.), 2 weeks before full bloom (6 May), and during rapid fruit growth (4 Aug.). Where B was used, it was applied to all leaves on each selected shoot/branch (described below). The distal 75% length of each leaf blade was immersed for 5 s in a 100 m M B solution supplied as 10 B-enriched boric acid (99.43% 10 B : 0.57% 11 B, Eagle Picher, Inc., Quapaw, Okla.). This approach was required to avoid contamination of the petiole with isotopically enriched B. The B solution contained 0.05% (v/v) L-77 (Loveland Industries Inc., Greeley, Colo.) as a surfactant and was adjusted to pH 5.5 with 0.1 mol·L –1 of NaOH. Care was taken not to contaminate nontreated plant parts, which included petioles, inflorescences, peduncles, and fruits, and which, along with treated leaves, were sampled for B analysis at 1, 5, and 15 d after the treatments were applied. BORON TRANSLOCATION FROM 1-YEAR-OLD LEAVES (EXPT. 1). To study 10 B disappearance from 1-year-old leaves (defined as mature fully developed leaves formed during the previous growing season, and subtending an inflorescence in their axes), 12 branches on each of five replicate trees were selected. Boron was applied to the leaves of six branches of each tree on 21 Apr., and the other six branches were used as controls. Each of the six branches was randomly assigned a number. For the first sampling, leaves were collected in such a way that for branches 1 and 4, leaf node positions 1 and 4 (counting from the basal) were sampled; for branch 2 and 5, leaf node positions 2 and 5 were sampled; for branch 3 and 6, leaf node positions 3 and 6 were sampled. For the second and third sampling, the leaf node position was varied accordingly to avoid systematic sampling error. Each sampling date replicate consisted of 24 leaves with four leaves from each branch.