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Atmospheric carbon dioxide (CO2) concentrations are increasing and may exceed 800 ppm by 2100. This is increasing global mean temperatures and the frequency and severity of heatwaves. Recently, we showed for the first time that the combination of short-term warming and elevated carbon dioxide (eCO2) caused extreme upward bending (i.e., hyponasty) of leaflets and leaf stems (petioles) in tomato (Solanum lycopersicum), which reduced growth. Here, we examined additional species to test the hypotheses that warming + eCO2-induced hyponasty is restricted to compound-leaved species, and/or limited to the Solanaceae. A 2 × 2 factorial experiment with two temperatures, near-optimal and supra-optimal, and two CO2 concentrations, ambient and elevated (400, 800 ppm), was imposed on similarly aged plants for 7–10 days, after which final petiole angles were measured. Within Solanaceae, compound-leaf, but not simple-leaf, species displayed increased hyponasty with the combination of warming + eCO2 relative to warming or eCO2 alone. In non-solanaceous species, hyponasty, leaf-cupping, and changes in leaf pigmentation as a result of warming + eCO2 were variable across species. [ABSTRACT FROM AUTHOR]

We previously showed that chronic warming plus elevated carbon dioxide (eCO2) causes extreme upward bending of leaflets and petioles (i.e., hyponasty) in tomato (Solanum lycopersicum), which reduces growth. In that study, only two levels of CO2 (400, 700 ppm) and temperature (30, 37 °C) were tested in young vegetative plants, and the underlying mechanism for warming + eCO2 hyponasty was not investigated. In this study, warming + eCO2 hyponasty was evaluated in tomato across a range of temperatures and CO2 concentrations, and at multiple life stages. Based on their roles in thermal hyponasty, ethylene and auxin tomato mutants were examined, and light quality manipulated, to explore the mechanism for warming + eCO2 hyponasty. At eCO2 (800 ppm), the petiole angle increased roughly linearly with temperature from 30 to 38 °C. Under high temperature stress (38 °C), the petiole angle increased similarly at all eCO2 concentrations (600/800/1000 vs. 400 ppm). All life stages examined had an increased petiole angle in leaves developed during warming + eCO2, such that most leaves in juvenile plants exhibited hyponasty but only young growing leaves did so in adults. Auxin-insensitive mutants displayed a reduced petiole angle compared to auxin-sensitive, ethylene-sensitive, ethylene-insensitive, and non-mutant genotypes, indicating that auxin, but not ethylene, is likely a main component of this hyponastic response. Reduced far-red-to-red light plus increased blue light reduced petiole hyponasty compared to non-filtered white light during warming + eCO2. These results indicate that eCO2 affects the well-characterized thermal hyponastic response of leaves, which has implications for future plant responses to climate change. [ABSTRACT FROM AUTHOR]

Silicon (Si) is a plant-beneficial element that can alleviate the effects of abiotic and biotic stress. Plants are typically classified as Si accumulators based on foliar Si concentrations (‡1% Si on a dry weight basis for accumulators). By this definition, most greenhouse-grown ornamentals are low Si accumulators. However, plants that accumulate low foliar Si concentrations may still accumulate high Si concentrations elsewhere in the plant. Additionally, screening cultivars for variability in Si uptake has not been investigated for low Si accumulator species. Therefore, the objective of this study was to assess cultivar variability in Si accumulation and distribution in petunia (Petunia 3hybrida). Eight cultivars (Supertunia Black Cherry, Supertunia Limoncello, Supertunia Priscilla, Supertunia Raspberry Blast, Supertunia Royal Velvet, Supertunia Sangria Charm, Supertunia Vista Silverberry, and Supertunia White Improved) were grown in a commercial peat-based soilless substrate under typical greenhouse conditions. They were supplemented with either 2 mM potassium silicate (+Si) or potassium sulfate (-Si) at every irrigation. Silicon supplementation increased leaf dry mass (4.5%) but did not affect total dry mass. In plants not receiving Si supplementation, leaf Si ranged from 243 to 1295 mg·kg-1, stem Si ranged from 48 to 380 mg·kg-1, flower Si ranged from 97 to 437 mg·kg-1, and root Si ranged from 103 to 653 mg·kg-1. Silicon supplementation increased Si throughout the plant, but most predominantly in the roots. Leaf Si in the 2 mM Si treatment ranged from 1248 to 3541 mg·kg-1 (173% to 534% increase), stem Si ranged from 195 to 654 mg·kg-1 (72% to 376% increase), flower Si ranged from 253 to 1383 mg·kg-1 (74% to 1082% increase), and root Si ranged from 4018 to 10,457 mg·kg-1 (593% to 9161% increase). The large increase in root Si following supplementation shifted Si distribution within plants. In nonsupplemented plants, it ranged from 51.2% to 76.8% in leaves, 8.2% to 40.2% in stems, 2.8% to 23.8% in flowers, and 1.2% to 13.8% in roots. In Si-supplemented plants, it ranged from 63.5% to 67.7% in leaves, 10.5% to 22.6% in roots, 9.4% to 17.7% in stems, and 1.6% to 9.6% in flowers. This study indicates that petunia, a low foliar Si accumulator, can accumulate appreciable quantities of Si in roots when provided supplemental Si. [ABSTRACT FROM AUTHOR]

Atmospheric CO2 enrichment is expected to often benefit plant growth, despite causing global warming and nitrogen (N) dilution in plants. Most plants primarily procure N as inorganic nitrate (NO3-) or ammonium (NH4+), using membrane-localized transport proteins in roots, which are key targets for improving N use. Although interactive effects of elevated CO2, chronic warming and N form on N relations are expected, these have not been studied. In this study, tomato (Solanum lycopersicum) plants were grown at two levels of CO2 (400 or 700 ppm) and two temperature regimes (30 or 37∘C), with NO3- or NH4+ as the N source. Elevated CO2 plus chronic warming severely inhibited plant growth, regardless of N form, while individually they had smaller effects on growth. Although %N in roots was similar among all treatments, elevated CO2 plus warming decreased (1) N-uptake rate by roots, (2) total protein concentration in roots, indicating an inhibition of N assimilation and (3) shoot %N, indicating a potential inhibition of N translocation from roots to shoots. Under elevated CO2 plus warming, reduced NO3--uptake rate per g root was correlated with a decrease in the concentration of NO3--uptake proteins per g root, reduced NH4+ uptake was correlated with decreased activity of NH4+-uptake proteins and reduced N assimilation was correlated with decreased concentration of N-assimilatory proteins. These results indicate that elevated CO2 and chronic warming can act synergistically to decrease plant N uptake and assimilation; hence, future global warming may decrease both plant growth and food quality (%N). [ABSTRACT FROM AUTHOR]

Climate change will increase drought in many regions of the world. Besides decreasing productivity, drought also decreases the concentration (%) of nitrogen (N) and phosphorous (P) in plants. We investigated if decreases in nutrient status during drought are correlated with decreases in levels of nutrient-uptake proteins in roots, which has not been quantified. Drought-sensitive (Hordeum vulgare, Zea mays) and -tolerant grasses (Andropogon gerardii) were harvested at mid and late drought, when we measured biomass, plant %N and P, root N- and P-uptake rates, and concentrations of major nutrient-uptake proteins in roots (NRT1 for NO3, AMT1 for NH4, and PHT1 for P). Drought reduced %N and P, indicating that it reduced nutrient acquisition more than growth. Decreases in P uptake with drought were correlated with decreases in both concentration and activity of P-uptake proteins, but decreases in N uptake were weakly correlated with levels of N-uptake proteins. Nutrient-uptake proteins per gram root decreased despite increases per gram total protein, because of the larger decreases in total protein per gram. Thus, drought-related decreases in nutrient concentration, especially %P, were likely caused, at least partly, by decreases in the concentration of root nutrient-uptake proteins in both drought-sensitive and -tolerant species. [ABSTRACT FROM AUTHOR]

Atmospheric CO 2 enrichment is expected to often benefit plant growth, despite causing global warming and nitrogen (N) dilution in plants. Most plants primarily procure N as inorganic nitrate (NO 3 - ) or ammonium (NH 4 + ), using membrane-localized transport proteins in roots, which are key targets for improving N use. Although interactive effects of elevated CO 2 , chronic warming and N form on N relations are expected, these have not been studied. In this study, tomato (Solanum lycopersicum) plants were grown at two levels of CO 2 (400 or 700 ppm) and two temperature regimes (30 or 37°C), with NO 3 - or NH 4 + as the N source. Elevated CO 2 plus chronic warming severely inhibited plant growth, regardless of N form, while individually they had smaller effects on growth. Although %N in roots was similar among all treatments, elevated CO 2 plus warming decreased (1) N-uptake rate by roots, (2) total protein concentration in roots, indicating an inhibition of N assimilation and (3) shoot %N, indicating a potential inhibition of N translocation from roots to shoots. Under elevated CO 2 plus warming, reduced NO 3 - -uptake rate per g root was correlated with a decrease in the concentration of NO 3 - -uptake proteins per g root, reduced NH 4 + uptake was correlated with decreased activity of NH 4 + -uptake proteins and reduced N assimilation was correlated with decreased concentration of N-assimilatory proteins. These results indicate that elevated CO 2 and chronic warming can act synergistically to decrease plant N uptake and assimilation; hence, future global warming may decrease both plant growth and food quality (%N)., (© 2016 Scandinavian Plant Physiology Society.)