Jj. Oertli, NONHOMOGENEITY OF BORON DISTRIBUTION IN PLANTS AND CONSEQUENCES FOR FOLIAR DIAGNOSIS, Communications in soil science and plant analysis, 25(7-8), 1994, pp. 1133-1147
Soil and plant analyses are useful diagnostic tools only if they suppl
y adequate information about the current state and can predict effects
of different types of management. The prerequisites for reproducibili
ty and consistency may not be met with boron which is not distributed
homogeneously in plants. It accumulates in marginal areas and between
veins, is transported with the transpiration stream and accumulates at
terminal places of transpiration. The boron concentration within the
same leaf may vary 100-fold and foliar analyses represent an average v
alue only. Moreover, the boron content increases with the age of leave
s, and there is no indication of a homeostatic control of foliar boron
contents. Accurate, representative sampling may thus be difficult and
critical. An extreme case is shown where toxicity occurs in old leave
s and deficiency in new growth. The rate of transpiration greatly affe
cts boron transport into leaves and its distribution. Predictions must
thus take water relations into account.