High growth temperatures and high soil nitrogen do not alter differences in CO assimilation between invasive Phalaris arundinacea (reed canarygrass) and Carex stricta (tussock sedge).

Premise Of The Study: Global change in temperature and soil nitrogen availability could affect plant community composition, potentially giving an advantage to invasive species compared to native species. We addressed how high temperatures affected CO assimilation parameters for invasive Phalaris arundinacea and a sedge, Carex stricta, it displaces, in natural and controlled environments.

Methods: Photosynthetic parameters were measured in a wetland in Indiana, USA during the abnormally warm year of 2012.

Constitutively overexpressing a tomato fructokinase gene (LeFRK1) in cotton (Gossypium hirsutum L. cv. Coker 312) positively affects plant vegetative growth, boll number and seed cotton yield.

Increasing fructokinase (FRK) activity in cotton (Gossypium hirsutum L.) plants may reduce fructose inhibition of sucrose synthase (Sus) and lead to improved fibre yield and quality. Cotton was transformed with a tomato (Solanum lycopersicum L.

Plasticity of nitrogen allocation in the leaves of the invasive wetland grass, Phalaris arundinacea and co-occurring Carex species determines the photosynthetic sensitivity to nitrogen availability.

Phalaris arundinacea displaces the slower-growing, native sedge, Carex stricta, where nitrogen availability is high. Our aim was to address whether morphological and physiological traits associated with carbon gain for P. arundinacea and C.

Expression of AtSAP5 in cotton up-regulates putative stress-responsive genes and improves the tolerance to rapidly developing water deficit and moderate heat stress.

The regulation of gene expression is a key factor in plant acclimation to stress, and it is thought that manipulation of the expression of critical stress-responsive genes should ultimately provide increased protection against abiotic stress. The aim of this study was to test the hypothesis that the ectopic expression of the AtSAP5 (AT3G12630) gene in transgenic cotton (Gossypium hirsutum, cv. Coker 312) will improve tolerance to drought and heat stress by up-regulating the expression of endogenous stress-responsive genes.

The differential response of photosynthesis to high temperature for a boreal and temperate Populus species relates to differences in Rubisco activation and Rubisco activase properties.

Significant inhibition of photosynthesis occurs at temperatures only a few degrees ( View Article and Find Full Text PDF

The Arabidopsis ascorbate peroxidase 3 is a peroxisomal membrane-bound antioxidant enzyme and is dispensable for Arabidopsis growth and development.

Ascorbate peroxidase (APX) exists as several isoforms that are found in various compartments in plant cells. The cytosolic and chloroplast APXs appear to play important roles in antioxidation metabolism in plant cells, yet the function of peroxisomal APX is not well studied. In this study, the localization of a putative peroxisomal membrane-bound ascorbate peroxidase, APX3 from Arabidopsis, was confirmed by studying the green fluorescent protein (GFP)-APX3 fusion protein in transgenic plants.

The role of antioxidant enzymes in photoprotection.

The enzymatic component of the antioxidant system is discussed as one of the defensive mechanisms providing protection against excessive light absorption in plants. We present an analysis of attempts to improve stress tolerance by means of the creation of transgenic plants with elevated antioxidant enzyme activities and conclude that the effect of such transgenic manipulation strongly depends on the manner in which the stress is imposed. The following factors may diminish the differences in photosynthetic performance between transgenic plants and wild type under field conditions: effective functioning of the thermal dissipation mechanisms providing a primary line of defense against excessive light, long-term adjustments of the antioxidant system and other photoprotective mechanisms, the relatively low level of control over electron transport exerted by the Water-Water cycle, especially under warm conditions, and a decrease in the content of the transgenic product during leaf aging.

Compensation for PSII photoinactivation by regulated non-photochemical dissipation influences the impact of photoinactivation on electron transport and CO2 assimilation.

The extent to which PSII photoinactivation affects electron transport (PhiPSII) and CO2 assimilation remains controversial, in part because it frequently occurs alongside inactivation of other components of photosynthesis, such as PSI. By manipulating conditions (darkness versus low light) after a high light/low temperature treatment, we examined the influence of different levels of PSII inactivation at the same level of PSI inactivation on PhiPSII and CO2 assimilation for Arabidopsis. Furthermore, we compared PhiPSII at high light and optimum temperature for wild-type Arabidopsis and a mutant (npq4-1) with impaired capacities for energy dissipation.

Expression of an Arabidopsis vacuolar sodium/proton antiporter gene in cotton improves photosynthetic performance under salt conditions and increases fiber yield in the field.

Drought and salinity are two major limiting factors in crop productivity. One way to reduce crop loss caused by drought and salinity is to increase the solute concentration in the vacuoles of plant cells. The accumulation of sodium ions inside the vacuoles provides a 2-fold advantage: (i) reducing the toxic levels of sodium in cytosol; and (ii) increasing the vacuolar osmotic potential with the concomitant generation of a more negative water potential that favors water uptake by the cell and better tissue water retention under high soil salinity.

Long-term night chilling of cotton (Gossypium hirsutum) does not result in reduced CO assimilation.

The aim of this study was to characterise the response of CO assimilation (A) of cotton (Gossypium hirsutum L.) to short- and long-term exposures to night chilling. We hypothesised that short-term exposures to night chilling would induce reductions in g and, therefore, A during the following days, while growth of cotton plants for several weeks in cool night conditions would cause elevated leaf carbohydrate content, leading to the down-regulation of the capacity for A.

Transgenic overproduction of glutathione reductase does not protect cotton, Gossypium hirsutum (Malvaceae), from photoinhibition during growth under chilling conditions.

In some studies, tissues from plants that have been genetically transformed to overproduce antioxidant enzymes sustain less damage when abruptly exposed to short-term chilling in the laboratory. However, few studies have examined the performance of transgenic plants during longer-term growth under chilling conditions. We compared growth of transgenic cotton that overproduces glutathione reductase (GR+; ∼40-fold overproduction) to growth of the wild type in a controlled environment chamber as leaf temperature was lowered from 28° to 14°C over 9 d and for a subsequent 9-d period at 14°C.

Elevated chloroplastic glutathione reductase activities decrease chilling-induced photoinhibition by increasing rates of photochemistry, but not thermal energy dissipation, in transgenic cotton.

The effect of the overproduction of glutathione reductase (GR+) in cotton (Gossypium hirsutum L. cv.Coker 312) chloroplasts on the response of photosynthetic parameters to chilling in the light was examined.

Enhanced photochemical light utilization and decreased chilling-induced photoinhibition of photosystem II in cotton overexpressing genes encoding chloroplast-targeted antioxidant enzymes.

The aim of this study was to determine whether increases in stromal superoxide dismutase (SOD; EC 1.15.1.

Protecting cotton photosynthesis during moderate chilling at high light intensity by increasing chloroplastic antioxidant enzyme activity.

This study examined the effect of increasing chloroplastic superoxide dismutase (SOD), ascorbate peroxidase (APX), or glutathione reductase (GR) activity via plant transformation of cotton on the initial recovery of photosynthesis following exposures to 10 degrees C and high photon flux density (PFD). Growing wild-type or non-expressing segregate plants (controls) and transformants at two PFDs (600 micromol m(-2) s(-1) and full sun) resulted in a range of total antioxidant enzyme activities. Total SOD activities above that for control leaves grown in full sun did not substantially improve the recoveries of CO(2)-saturated photosynthesis, especially for stress treatments lasting more than 1 h, while elevated APX or GR activity did improve recoveries after 1-3 h of the chilling treatment.

Effects of mild night chilling on respiration of expanding cotton leaves.

Utilizing expanding leaves of cotton (Gossypium hirsutum L. cv. Coker 312), the hypothesis that suboptimal night temperatures above those for putative phase transitions of mitochondrial lipids caused greater substrate control of night respiration and increased the control that respiration exerted on ATP-dependent metabolism was tested.

Overexpression of Superoxide Dismutase Protects Plants from Oxidative Stress (Induction of Ascorbate Peroxidase in Superoxide Dismutase-Overexpressing Plants).

Photosynthesis of leaf discs from transgenic tobacco plants (Nicotiana tabacum) that express a chimeric gene that encodes chloroplast-localized Cu/Zn superoxide dismutase (SOD+) was protected from oxidative stress caused by exposure to high light intensity and low temperature. Under the same conditions, leaf discs of plants that did not express the pea SOD isoform (SOD-) had substantially lower photosynthetic rates. Young plants of both genotypes were more sensitive to oxidative stress than mature plants, but SOD+ plants retained higher photosynthetic rates than SOD- plants at all developmental stages tested.

Increased resistance to oxidative stress in transgenic plants that overexpress chloroplastic Cu/Zn superoxide dismutase.

Transgenic tobacco plants that express a chimeric gene that encodes chloroplast-localized Cu/Zn superoxide dismutase (SOD) from pea have been developed. To investigate whether increased expression of chloroplast-targeted SOD could alter the resistance of photosynthesis to environmental stress, these plants were subjected to chilling temperatures and moderate (500 mumol of quanta per m2 per s) or high (1500 mumol of quanta per m2 per s) light intensity. During exposure to moderate stress, transgenic SOD plants retained rates of photosynthesis approximately 20% higher than untransformed tobacco plants, implicating active oxygen species in the reduction of photosynthesis during chilling.

Changes in Activities of Enzymes of Carbon Metabolism in Leaves during Exposure of Plants to Low Temperature.

The aim of this study was to determine the response of photosynthetic carbon metabolism in spinach and bean to low temperature. (a) Exposure of warm-grown spinach and bean plants to 10 degrees C for 10 days resulted in increases in the total activities of a number of enzymes, including ribulose 1,5-bisphosphate carboxylase (Rubisco), stromal fructose 1,6 bisphosphatase (Fru 1,6-P(2)ase), sedoheptulose 1,7-bisphosphatase (Sed 1,7-P(2)ase), and the cytosolic Fru 1,6-P(2)ase. In spinach, but not bean, there was an increase in the total activity of sucrose-phosphate synthase.

Differential expression of ribulose-1,5-bisphosphate carboxylase in reciprocal F1 hybrids of a C3 and a C4-like Flaveria species.

Stable reciprocal hybrids between Flaveria pringlei (C3) and F. brownii (C4-like) have been produced by standard breeding techniques. There are no differences in the isoelectric focusing patterns of the catalytic subunits of the ribulose-1,5-bisphosphate carboxylase/oxygenase from F.

Effect of pH on the Kinetic Parameters of NADP-Malic Enzyme from a C(4)Flaveria (Asteraceae) Species.

We have used the pH variation in the kinetic parameters with respect to malate of NADP-malic enzyme purified from the C(4) species, Flaveria trinervia, to compare the pK values of its functional groups with those for the pigeon liver NADP-malic enzyme (MI Schimerlik, WW Cleland [1977] Biochemistry 16: 576-583) and the plant NAD-malic enzyme (KO Willeford, RT Wedding [1987] Plant Physiol 84: 1084-1087). Like the other enzymes, the C(4) enzyme has a group with a pK of about 6.0 (6.

Enzymic and Photosynthetic Characteristics of Reciprocal F(1) Hybrids of Flaveria pringlei (C(3)) and Flaveria brownii (C(4)-Like Species).

The activities of key C(4) enzymes in gel-filtered, whole-leaf extracts and the photosynthetic characteristics for reciprocal F(1) hybrids of Flaveria pringlei (C(3)) and F. brownii (C(4)-like species) were measured to determine whether any inherited C(4)-photosynthetic traits are responsible for their reduced CO(2) compensation concentration values (AS Holaday, S Talkmitt, ME Doohan Plant Sci 41: 31-39). The activities of phosphoenolpyruvate carboxylase, pyruvate, orthophosphate dikinase, and NADP-malic enzyme (ME) for the reciprocal hybrids are only about 7 to 17% of those for F.

Photosynthetic/photorespiratory characteristics of C3-C 4 intermediate species.

The extent of photorespiration, the inhibition of apparent photosynthesis (APS) by 21% O2, and the leaf anatomical and ultrastructural features of the naturally occurring C3-C4 intermediate species in the diverse Panicum, Moricandia, and Flaveria genera are between those features of representative C3 and C4 plants. The greatest differences between the photosynthetic/photorespiratory CO2 exchange characteristics of the C3-C4 intermediates and C3 plants occur for the parameters which are measured at low pCO2 (i.e.

C3-C 4 Intermediate species in the genus Flaveria: leaf anatomy, ultrastructure, and the effect of O2 on the CO 2 compensation concentration.

Leaf anatomical, ultrastructural, and CO2-exchange analyses of three closely related species of Flaveria indicate that they are C3-C4 intermediate plants. The leaf mesophyll of F. floridana J.