ISHS Acta Horticulturae 531: II ISHS Conference on Fruit Production in the Tropics and Subtropics
ROLE OF STOMATAL OPENING FOR THE UPTAKE OF FOLIAR FERTILIZERS BY TREE CROPS IN THE HUMID TROPICS (AMAZONIA, BRAZIL) |
| Authors: | J. Burkhardt, G. Schroth |
| Keywords: | Citrus sinensis, Bixa orellana, Hevea brasiliensis, cuticle, foliar fertilization, stomata |
| Abstract:
The possibility of stomatal uptake of ions has recently been demonstrated, contrary to the widespread opinion rejecting this possibility for physical reasons. We tested the importance of stomatal uptake of foliar applied nutrients into leaves under field conditions, at a research site near Manaus, central Amazonia, Brazil, on orange (Citrus sinensis), annatto (Bixa orellana) and rubber (Hevea brasiliensis) plants. Different concentrations of 15N labelled NaNO3 and K2HPO4 were applied, either during the day (open stomata) or shortly after sunset (stomata closed). Leaves and twigs were sampled three hours after nutrient application, washed and dried, and analyzed for 15N and phosphate, respectively. A significantly higher uptake of 15 nitrate was found for the day treatment compared to the treatment at night. Relocation of N from leaves to twigs was found to be negligible. These results could not be confirmed for phosphate due to reduced analytical sensitivity. Although a certain influence of humidity conditions cannot be ruled out, the results suggest that stomatal uptake was an important factor of overall uptake of N into the leaves and that stomatal closure during the night hindered the uptake of ions. A more mechanistic understanding of the processes involved in nutrient uptake by leaves will help to improve the efficiency of foliar fertilization. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
