Boron alleviates aluminum toxicity in pea (Pisum sativum)

Abstract

One important target of boron (B) deficiency and aluminum (Al) toxicity is cell wall. Thus we studied the hypothesis that B is capable of alleviating Al toxicity in pea (Pisum sativum). Short-term and prolonged Al exposure to pea roots at different B levels was carried out on uniform seedlings precultured at a low B level. When seedlings with a low B level were supplied with or without B for 1 and 2 days before 24 h Al exposure, roots were longer while root diameter was thinner after B addition especially for 2 days even with exposure to Al; root elongation was inhibited while root diameter was enlarged by Al exposure. Callose induction by Al toxicity was higher with B added, but this was reversed after the removal of the cotyledons. Hematoxylin staining was lighter in the root tips given B, and Al content in the root tips and cell walls dropped after exposure to B. This indicates that B alleviated Al toxicity in the root tips during short-term Al exposure by decreasing Al binding in root cell walls. An increase in chlorophyll and biomass and reduced chlorosis were found at the higher level of B during prolonged Al treatment, which was coincided with the decreased Al contents, indicating that B alleviated Al toxicity to shoots. B supplementation alleviates some of the consequences of Al toxicity by limiting some Al binding in cell walls, resulting in less injury to the roots as well as less injury to the shoots.

How do Citrus Crops Cope with Aluminum Toxicity?

“…Confirming these findings, Jiang et al Role of boron and phosphorous on aluminum toxicity An investigation was conducted (Jiang et al, 2009b) with Citrus grandis L. seedlings to determine how boron alleviates Al-induced inhibition of root and shoot growth and results confirmed that inhibition of root and shoot growth is not due to Al-induced boron deficiency, but due to Al toxicity. Their findings on preventive measures of boron are in line with the results of Yu et al (2009), who conducted a similar study with pea (Pisum sativam). According to Jiang et al (2009b), boron induced changes in Al speciation and/or sub-cellular compartmentation would be the reason behind amelioration of root inhibition in citrus, which has previously stated by Corrales et al (2008) also.…”

Boron supply alleviates Al-induced inhibition of root elongation and physiological characteristics in rapeseed (Brassica napusL.)

“…The selected roots were stained by the Yu et al (2009) method. After soaking in a solution of 0.2% hematoxylin and 0.02% KI, the plant roots were washed with de-ionized water until no dye in the rinsing water and studied under stereomicroscope and images were taken with Nikon digital camera.…”

“…For determination of Al concentrations in leaves and roots (0-10 mm root apices), the roots were washed 3 times with 0.5 mM CaCl 2 solution, and Al concentrations were determined by graphite furnace atomic absorption spectrophotometer (GTA 120 Graphite Tube Atomizer, Agilent Technologies, 200 series AA) as described by Yu et al (2009). B contents in leaves and roots were measured by Dible et al (1954) method.…”

“…So this complex network of cells makes the cell wall tighter and hinders the entrance of Al into the cell, thus preventing Al contact with cell organelles (O'Neill et al 2004;Corrales et al 2008). Amelioration of Al toxicity by using B has been stated by many researchers in squash (LeNoble et al 1996b), alfalfa (LeNoble et al 1996a), sour pummel (Jiang et al 2009), pea (Yu et al 2009), sunflower (Ruiz et al 2006), common bean (Stass et al 2007), rapeseed (Yan et al 2018), trifoliate (Riaz et al 2018a(Riaz et al , 2018b and however, such an effect was not found by Wang et al (2005) in maize. Many reports have indicated the mechanism behind B-induced alleviation of Al-toxicity, yet the actual mechanism has not been clarified.…”

“…Many reports have indicated the mechanism behind B-induced alleviation of Al-toxicity, yet the actual mechanism has not been clarified. Some researchers proposed that B application prevented binding sites for Al, and reduced Al direct contact with roots (Stass et al 2007;Yu et al 2009), and this lower Al uptake prevents in the decrease of photosynthesis and alleviates the chlorosis symptoms of Al toxicity (Jiang et al 2009;Yu et al 2009). …”