Elevated CO2 affects plant responses to variation in boron availability

Abstract

Aim Effects of elevated CO 2 on N relations are well studied, but effects on other nutrients, especially micronutrients, are not. We investigated effects of elevated CO 2 on response to variation in boron (B) availability in three unrelated species: seed geranium (Pelargonium x hortorum), barley (Hordeum vulgare), and water fern (Azolla caroliniana). Methods Plants were grown at two levels of CO 2 (370, 700 ppm) and low, medium, and high B. Treatment effects were measured on biomass, net photosynthesis (P n ) and related variables, tissue nutrient concentrations, and B transporter protein BOR1. Results In geranium, there were interactive effects (P< 0.05) of B and CO 2 on leaf, stem, and total plant mass, root:shoot ratio, leaf [B], B uptake rate, root [Zn], and P n . Elevated CO 2 stimulated growth at 45 μM B, but decreased it at 450 μM B and did not affect it at 4.5 μM B. P n was stimulated by elevated CO 2 only at 45 μM B and chlorophyll was enhanced only at 450 μM B. Soluble sugars increased with high CO 2 only at 4.5 and 45 μM B. High CO 2 decreased leaf [B] and B uptake rate, especially at 450 μM B. Though CO 2 and B individually affected the concentration of several other nutrients, B x CO 2 interactions were evident only for Zn in roots, wherein [Zn] decreased under elevated CO 2 . Interactive effects of B and CO 2 on growth were confirmed in (1) barley grown at 0, 30, or 1,000 μM B, wherein growth at high CO 2 was stimulated more at 30 μM B, and (2) Azolla grown at 0, 10, and 1,000 μM B, wherein growth at high CO 2 was stimulated at 0 and 10 μM B. Conclusion Thus, low and high B both may limit growth stimulation under elevated vs. current [CO 2 ], and B deficiency and toxicity, already common, may increase in the future.

Heat Stress Decreases Levels of Nutrient-Uptake and -Assimilation Proteins in Tomato Roots

“…Total protein was extracted from tissue as in [40], by grinding 400 mg of frozen root tissue in liquid N 2 in a mortar and pestle and then in 2 mL of extraction buffer of the following composition: 0.5 M Tris pH-8, 0.1 M potassium chloride, 0.9 M sucrose, 50 mM ethylene diamine tetra-acetic acid, 2% ( v : v ) β-mercaptoethanol, 10 µM leupeptin, and 1 mM phenyl methyl sulfonyl fluoride. The homogenate was transferred to a 15-mL tube, to which was added 2 mL volume of phenol, and then the tubes were incubated for 20 min at room temperature and centrifuged at 5600 rcf (relative centrifugal force) for 15 min at 4 °C to separate aqueous and organic phases.…”

“…The relative amount of nutrient-uptake proteins per unit total root protein was determined by quantitative ELISA (enzyme-linked immunosorbent assay), using protein-specific antibodies to oligopeptides of conserved domains of target proteins; conserved domains determined using bioinformatics techniques, as described in [40]. Antiserum specificity was confirmed with immune (western) blotting (immune vs. pre-immune serum, and antigen-purified vs. crude serum, in both tomato and arabidopsis), and pre-immune serum was used during ELISA to subtract signal attributable to non-specific binding.…”

The Levels of Boron‐Uptake Proteins in Roots are Correlated with Tolerance to Boron Stress in Barley

“…We have designed antibodies to highly conserved domains of both main B-transporter proteins, BOR1, NIP5;1, and we have used these antibodies to measure the levels of each transporter in response to levels of B in various species (Mishra et al, 2012). We have designed antibodies to highly conserved domains of both main B-transporter proteins, BOR1, NIP5;1, and we have used these antibodies to measure the levels of each transporter in response to levels of B in various species (Mishra et al, 2012).…”

“…Total root protein was extracted from plants following a modified phenol extraction method as mentioned in Mishra et al (2012). Briefly, 500 mg frozen root tissues of individual replicates of each cultivar were ground into powder in the presence of liquid N in a mortar and pestle and then reground after addition of 2 mL of extraction buffer (0.2 M Tris-HCl [pH 8.0], 5 mM ethylenediaminetetraacetic acid [EDTA], 1% sodium dodecyl sulfate [SDS], 0.7 M sucrose, 2% b mercaptoethanol, 1 mM phenylmethane sulfonyl fluoride [PMSF], and 1 mM leupeptin).…”

“…However, to date, no previous studies have investigated interspecific or intraspecific variation in expression of B-uptake proteins at the protein level to determine if variation in tolerance to either suboptimal or supraoptimal B availability is related to variation in b-stress tolerance. We have designed antibodies to highly conserved domains of both main B-transporter proteins, BOR1, NIP5;1, and we have used these antibodies to measure the levels of each transporter in response to levels of B in various species (Mishra et al, 2012). In the present study, we used these antibodies to quantify expression of BOR1 and NIP5;1 protein in roots of two barley cultivars that differ in tolerance to sub-and supraoptimal B levels to determine if genotypic variation in plant tolerance to B stress is correlated with natural levels of B-uptake proteins in roots.…”