ISHS Acta Horticulturae 700: International Symposium Towards Ecologically Sound Fertilisation Strategies for Field Vegetable Production
AMBIENT AIR HUMIDITY AFFECTS PHLOEM MOBILITY OF FOLIAR-APPLIED BORON |
| Authors: | T. Eichert, H.E. Goldback |
| Keywords: | boric acid, relative humidity, Ricinus communis, sieve-tube sap, xylem |
| Abstract:
Foliar fertilization is a common method for the correction of B deficiency. However, plant parts not directly hit by the B-spray (e.g. roots) often do not benefit from this measure. The reason for B immobility is not fully understood. We studied the effect of ambient air humidity on phloem mobility of foliar-applied B. In Ricinus communis seedlings with cut hypocotyls B concentrations in phloem sap reached up to 100% of the B concentrations applied to the cotyledons. In a second experiment B mobility was studied using intact Ricinus seedlings. At high relative air humidity (r.h.) B applied to the cotyledons was transported to hypocotyls and roots, whereas at low r.h. no translocation of B was detectable. It is concluded that ambient air humidity controls phloem mobility of B via its effect on the xylem flow rate: if the xylem flow rate is low or xylem flow is interrupted foliar-applied B becomes mobile. | |
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