Boron uptake by excised barley roots: I. Uptake into the free space

Use of an (n, α) nuclear reaction to study the long-distance transport of boron in trifolium repens after foliar application

The growth of white clover (Trifolium repens L.) is severely inhibited by boron starvation, but a foliar treatment with boric acid can transitorily alleviate the deficiency symptoms. The (10)B(n ,α)(7) Li nuclear reaction has been used to study boron transport in the plant after foliar application. More than 98% of the boron supplied remained at the point where it was applied to the leaves, and less than 2% was useful to the growth of the treated plant. This small "efficient" portion of boron was quite mobile. It was distributed to the different parts of the plant, then was transferred from the oldest parts to the newly formed leaves. Physiological and agronomical implications of these data are discussed.

Borate Exchanges of Lemna minor L. as Studied with the Help of the Enriched Stable Isotopes and of a (n,alpha) Nuclear Reaction

Despite the lack of a convenient radioisotope of boron, it is possible to measure unidirectional fluxes of borate between cellular systems and their external medium. It was accomplished by using the two purified stable isotopes ((10)B and (11)B), with (10)B specifically detected by a (n,alpha) nuclear reaction. The method was applied to compartmental analysis of borate with intact plants of Lemna minor L. Four compartments were suggested. Three of them apparently correspond to the three classical ones: free space (including easily dissociable borate monoesters), cytoplasm, and vacuole. The fourth one was interpreted as corresponding to very stable borate diesters in the cell walls. The method allows the determination of the borate capacities of the various compartments and of the borate unidirectional fluxes between the different compartments, at borate flux equilibrium. Other physicochemical data (mono and diester mass action constants, turn over numbers) were evaluated. The results are consistent with what is known of pure substances.