Interactions between aluminum and boron in tea (Camellia sinensis) plants

Abstract

Response of tea plants (Camellia sinensis (L.) O. Kontze) to Al (300 lM AlCl 3 for 14 weeks) was studied in combination with deficient (-B) or adequate B supply (?B) in hydroponics. Aluminum improved plant growth under B deficiency. This positive Al effect in (-B) plants was related to an Al-induced increase of B contents in the root cell walls (CW). Moreover, in (-B) plants more Al was partitioned into CW-bound fractions in both leaves and roots than in (?B) plants; an indication that B deficiency reduced the mobility of Al in the tea plants. In general, the highest activities of phenylalanine ammonia lyase, polyphenol oxidase, and soluble and CW-bound fractions of peroxidases were observed in (?Al/-B) plants. In (-B) plants Al supply caused a reduction of CW-bound phenolic acids and lignin, while the concentrations of soluble phenolics increased in the leaves. In the roots, however, Al treatment of B-deficient plants caused a significant increase of CW-bound phenolic acids, but not of lignin. Our results suggest that increased B partitioning into CW and reduction of lignification were important causes for Al-mediated amelioration of growth in B-deficient plants. In addition, the observation that in (?Al/-B) roots CW binding of both Al and phenolic acids was enhanced indicates that in the B-deficient roots Al was mainly bound to the CW phenolic acids; this, in turn, reduced their availability for enzymatic reactions and lignin synthesis.

Expression patterns and promoter analyses of aluminum-responsive NAC genes suggest a possible growth regulation of rice mediated by aluminum, hormones and NAC transcription factors

“…Moreover, Al promotes nutrient uptake by inducing the expression or activity of transport proteins (channels and transporters) and changes in the membrane potential and proton flux (H + ) [77,78,79]. Indeed, Al can activate channels and Mg transporters in Al-resistant plants [80], and improves plant performance under nutrient deficiencies of B [81,82] and P [83]. Al also prevents Fe toxicity by reducing Fe content in leaves and roots [84,85,86].…”

Aluminum, a Friend or Foe of Higher Plants in Acid Soils

“…Also, Al improves plant growth under nutrient deficiency; for example, supplementation with Al enhanced the growth of tea plants deficient in boron (B). Under B deficiency conditions, Al was able to positively regulate the metabolism of N and carbon (C) and antioxidant defense activity, while increasing the uptake and transportation of B in tea plants ( Hajiboland et al, 2014 , 2015 ). Under limiting conditions of P, Al stimulates P uptake in microalgae ( Zhou L. et al, 2016 ).…”

How Plants Handle Trivalent (+3) Elements

“…The positive effect of aluminum (Al) on B deficient tea plants provides indirect support to this hypothesis. In B deficient tea roots, Al is mainly bound to cell wall phenolics, thus reducing their availability for enzymatic reactions and lignin biosynthesis [14].…”

“…In fact, surplus B ameliorates Al toxicity in different species [126,127]. In turn, Al has a positive effect on B-deficient tea plants [14]. In rice, B-pretreatment reduces Al-binding to the cell wall pectins and increases the expression of the OsSTAR1/STAR2 involved in reducing the accumulation of Al in cell walls.…”

“…Boron enhances antioxidant defenses in Al-stressed plants [128,129]. Aluminum, in turn, may improve the performance of B-deficient plants by binding excess polyphenols in the cell wall [14].…”