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Drought invokes a variety of metabolic alterations in plant leaves to cope with stress situations. To understand the effects of CO2 and drought stress for leaf metabolic changes in potato [Solanum tuberosum (L)], two contrasting potato cultivars Harley Blackwell (HB, an early maturing, newer cultivar) and Snowden (SD, an established, full-season cultivar) were tested under water-limited conditions and CO2 enrichment. The results revealed that most of the drought-triggered metabolites were lower in HB compared to SD. However, HB showed quicker adjustments in the metabolic processes such as conversion of starch into soluble sugars and biosynthesis of phenylalanine and other compatible solutes at the early stages of the drought progression. Moreover, the existence of genotypic differences for leaf water potential (LWP) in response to CO2 enrichment was evident. Our study provides insights into the possible metabolic strategies of drought tolerance in potato cultivars under ambient and elevated CO2. [ABSTRACT FROM AUTHOR]

Detached leaves at top canopy structures always experience higher solar irradiance and leaf temperature under natural conditions. The ability of tolerance to high temperature represents thermotolerance potential of whole-plants, but was less of concern. In this study, we used a heat-tolerant (B76) and a heat-susceptible (B106) maize inbred line to assess the possible mitigation of sudden heat shock (SHS) effects on photosynthesis (PN) and C4 assimilation pathway by elevated [CO2]. Two maize lines were grown in field-based open top chambers (OTCs) at ambient and elevated (+180 ppm) [CO2]. Top-expanded leaves for 30 days after emergence were suddenly exposed to a 45°C SHS for 2 hours in midday during measurements. Analysis on thermostability of cellular membrane showed there was 20% greater electrolyte leakage in response to the SHS in B106 compared to B76, in agreement with prior studies. Elevated [CO2] protected PN from SHS in B76 but not B106. The responses of PN to SHS among the two lines and grown CO2 treatments were closely correlated with measured decreases of NADP-ME enzyme activity and also to its reduced transcript abundance. The SHS treatments induced starch depletion, the accumulation of hexoses and also disrupted the TCA cycle as well as the C4 assimilation pathway in the both lines. Elevated [CO2] reversed SHS effects on citrate and related TCA cycle metabolites in B106 but the effects of elevated [CO2] were small in B76. These findings suggested that heat stress tolerance is a complex trait, and it is difficult to identify biochemical, physiological or molecular markers that accurately and consistently predict heat stress tolerance. [ABSTRACT FROM AUTHOR]

A detailed investigation of the concentration (e.g., mg g-1 seed) and total yield (e.g., g plant-1) of seed mineral elements and metabolic profile under phosphorus (P) starvation at ambient (aCO2) and elevated carbon dioxide (eCO2) in soybean is limited. Soybean plants were grown in a controlled environment at either sufficient (0.50 mM P, control) or deficient (0.10 and 0.01 mM, P-stress) levels of P under aCO2 and eCO2 (400 and 800 mmol mol-1, respectively). Both the concentration and yield of 36 out of 38 seed components responded to P treatment and on average 25 and 11 components increased and decreased, respectively, in response to P starvation. Concentrations of carbohydrates (e.g., glucose, sugar alcohols), organic acids (e.g., succinate, glycerate) and amino acids increased while oil, and several minerals declined under P deficiency. However, the yield of the majority of seed components declined except several amino acids (e.g., phenylalanine, serine) under P deficiency. The concentration-based relationship between seed protein and oil was negative (r² = 0.96), whereas yield-based relationship was positive (r² = 0.99) across treatments. The CO2 treatment also altered the concentration of 28 out of 38 seed components, of which 23 showed decreasing (e.g., sucrose, glucose, citrate, aconitate, several minerals, and amino acids) while C, iron, Mn, glycerate, and oil showed increasing trends at eCO2. Despite a decreased concentration, yields of the majority of seed components were increased in response to eCO2, which was attributable to the increased seed production especially near sufficient P nutrition. The P × CO2 interactions for the concentration of amino acids and the yield of several components were due to the lack of their response to eCO2 under control or the severe P starvation, respectively. Thus, P deficiency primarily reduced the concentration of oil and mineral elements but enhanced a majority of other components. However, seed components yield consistently declined under P starvation except for several amino acids. The study highlighted a P nutritional-status dependent response of soybean seed components to eCO2 suggesting the requirement of an adequate P supply to obtain the beneficial effects of eCO2 on the overall yield of various seed components. [ABSTRACT FROM AUTHOR]