Boron foliar fertilization of soybean and lychee: Effects of side of application and formulation adjuvants

Abstract

Experiments to assess the rate of absorption and translocation of foliar‐applied, isotopically labeled boric acid (BA) were carried out with lychee (Litchi chinensis Sonn.) and soybean (Glycine max [L.] Merr.) plants. Boron (B) absorption and translocation within the plant, one week after treatment, was investigated after adding to the boric acid (BA solutions 0.5 mM CaCl2 and/or 50 or 500 mM sorbitol). The contribution of stomata to the absorption process was assessed by applying the solutions either to the adaxial or to the abaxial leaf side. Both plant species differed greatly in total absorption rates. The adaxial leaf surface (lacking stomata) of lychee leaves was nearly impermeable, while the stomatous abaxial surface was permeable to BA solutions. In this species, no translocation of 10B to other leaf parts and no effect of adjuvants in increasing 10B absorption were recorded. In contrast, 10B was absorbed both by adaxial and abaxial leaf surfaces of soybean leaves. Boron concentrations measured in treated soybean leaves were sixfold higher after application to the abaxial as compared to the adaxial leaf surface. The addition of adjuvants significantly enhanced the rate of 10B absorption, but not its translocation within the plant. Treatments containing 500 mM sorbitol led to increased 10B absorption and enhanced acropetal 10B movement, whereas adding only 50 mM sorbitol had no significant effect. Application of 0.5 mM CaCl2 in combination with 500 mM sorbitol decreased the rate of 10B absorption, compared to the performance of 500 mM sorbitol alone. Basipetal 10B translocation was very limited. A distinct effect of B‐sorbitol complexes on B translocation apart from the pure adjuvant effect could not be discerned in this investigation.

Stomatal penetration by aqueous solutions – an update involving leaf surface particles

“…In summary, the observed effects on plant physiological parameters support the hypothesis that abaxial uptake is stronger than adaxial uptake in apple leaves, consistent with results from a recent study on lychee leaves that used boron isotopes as a tracer (Will et al ., ). The difference in uptake is most probably related to the different structures of the two leaf sides.…”

“…The a priori exclusion of stomatal liquid water transfer restricted the uptake and loss of liquid water and aqueous solutions to the cuticular part of the leaf surface. However, there has also been a steadily increasing number of experimental reports from different backgrounds that have pointed to the stomatal uptake of water (Burgess & Dawson, ; Breshears et al ., ; Limm et al ., ; Simonin et al ., ), nutrients (Fernandez et al ., ; Will et al ., ), ionic fluorescent dyes (Eichert et al ., ; Eichert & Burkhardt, ) and abscisic acid (Wilkinson & Davies, ) without the use of surfactants. The main argument against such conflicting observations was the possibility of spatial, temporal or spatiotemporal cuticular heterogeneities (e.g.…”

Boron deficiency in woody plants: various responses and tolerance mechanisms

“…The effects of B application in woody plants are influenced by fertilization methods ( Nyomora et al, 1999 ; Boaretto et al, 2011 ) and for foliar applications by leaf surface characteristics ( Perica et al, 2001b ; Will et al, 2012 ). Unlike annual plants, trees are perennial and commonly suffer from long-term B deficiency.…”

The dynamic state of the ionome in roots, nodules, and shoots of soybean under different nitrogen status and at different growth stages

“…15 of the 17 essential elements for plants are also considered essential for Rhizobium : C, Ca, Cu, Fe, H, K, Mg, Mn, Mo, N, Ni, O, P, S, and Zn. These elements play various roles in the symbiosis between legumes and Rhizobium , acting as part of the nitrogenase ( Mendel , 2011), as cofactors that participate in N 2 fixation and stabilize cell membranes for N uptake ( Mendel , 2011; Fester et al, 2014), as crucial signals for bacteroid differentiation to the N 2 ‐fixing form of Rhizobium ( Will et al, 2012), and satisfying energy supply in the form of ATP for nitrogenase function ( Rubio et al, 2012).…”