Articles
AMBIENT AIR HUMIDITY AFFECTS PHLOEM MOBILITY OF FOLIAR-APPLIED BORON
Article number
700_6
Pages
67 – 70
Language
English
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.
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.
Publication
Authors
T. Eichert, H.E. Goldback
Keywords
boric acid, relative humidity, Ricinus communis, sieve-tube sap, xylem
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