Foliar Carbohydrate Research Articles

Photosynthesis and Photosynthate Partitioning in N2-Fixing Soybeans

Leaf area, chlorophyll content, net CO(2) photoassimilation, and the partitioning of fixed carbon between leaf sucrose and starch and soluble protein were examined in Glycine max (L) Merr. cv Williams grown under three different nitrogen regimes. One group (Nod+/+) was inoculated with Bradyrhizobium and watered daily with a nutrient solution containing 6 millimolar NH(4)NO(3). A second set (Nod+/-) was inoculated and had N(2) fixation as its sole source of nitrogen. A third group (Nod(-)) was not inoculated and was watered daily with a nutrient solution containing 6 millimolar NH(4)NO(3). The mean net micromole CO(2) uptake per square decimeter per hour of the most recently matured source leaves was similar among the three groups of plants, being about 310. Mean leaf area of the source leaves, monitored for net photosynthesis was also similar. However, the mean milligram of chlorophyll per square decimeter of Nod+/- test leaves was about 50% lower than the other groups' leaves and indicated nitrogen deficiency. Thus, Nod+/- utilized their chlorophyll more efficiently for photosynthetic CO(2) uptake than the plants of the other treatments. The ratio of foliar carbohydrate:protein content was high in Nod+/- but low in the plants from the other two treatments. This inverse relationship between foliar protein and carbohydrate content suggests that more fixed carbon is diverted to the synthesis of protein when nitrogen availability is high. It was also found that Nod+/- sequestered more storage protein in their paraveinal mesophyll than plants of the other treatments. This study indicates that when inorganic nitrogen regimes are used to control photosynthate partitioning, then both leaf carbohydrate and leaf protein must be considered as end products of carbon assimilate allocation.

Influence of mist pH and acid anion on cation efflux from pinto bean foliage

The cation content of droplets collected from Phaseolus vulgaris (pinto bean) leaf surfaces during misting was more strongly influenced by mist pH (2.5, 4.0, or deionized water) than by source of acidity (HCI or H2SO4 + HNO3). Concentrations of Ca2+, Mg2+, and K+ were highest in droplets from leaves treated with the pH 2.5 mists, but there were often no differences between the pH 4.0 and deionized water treatments. Cation content and pH of droplets from leaves treated with pH 2.5 mists increased across the three days of treatment, while those from leaves treated with less acidic mists decreased or did not change across the days of treatment. Source of acidity often affected foliar concentrations of Mg2+, K+, and Na+, but in inconsistent directions, and foliar concentrations of Mg2+ and K+ were unaffected by mist pH. Foliar Ca 2+ concentrations were often highest in leaves treated with pH 2.5 mists, in contrast to expectation, perhaps because of effects of acidic mist on foliar carbohydrate status. Despite the large efflux of cations from leaves treated with pH 2.5 mists, foliar cation concentrations in nonmisted foliage were sometimes lower than in misted foliage (Ca2+), but were higher in other cases (Na+) or indistinguishable in still others (K−). While exposure of plants to highly acidic mists appeared to cause accelerated efflux of foliar cations, effects on foliar chemistry are probably dependent on soil nutrient status and on other aspects of plant vigor.

Net CO2 Assimilation and Carbohydrate Partitioning of Grapevine Leaves in Response to Trunk Girdling and Gibberellic Acid Application

Leaf net CO(2) assimilation rate (A), stomatal conductance (g(s)), carboxylation efficiency, and foliar nonstructural carbohydrates were measured on mature, field-grown Vitis vinifera L. (cv Thompson Seedless) vines that had been trunk girdled, sprayed with gibberellic acid, or both, shortly after anthesis. Girdling reduced A, g(s), and carboxylation efficiency when measured 2 weeks after imposition of the treatments. Diurnal measurements indicated that A of girdled vines was less than that of control vines between 1000 and 1800 hours. Gibberellic acid mitigated the depressing effect of girdling on g(s) during the same diurnal measurements. The concentrations of foliar carbohydrates were greatest for the girdled vines, followed by the combination treatment and were lowest for the control vines. Foliar carbohydrates were greater for girdled vines 4 weeks after the treatments were imposed, however, by this time there was no significant difference in A between the control and girdled vines. Two and 4 weeks after the experiment was initiated root carbohydrate concentrations were less for the girdled vines when compared to the control vines. The data indicate that the reduction in A of girdled grapevines is not associated with the accumulation of leaf nonstructural carbohydrates following the girdling treatment.

Effects of N, Temperature, and Moisture Stress on the Growth and Physiology of Creeping Bentgrass and Response to Chelated Iron1

AbstractBentgrass (Agrostis palustris Huds.) turf often will improve in turf quality with applications of Fe during various times of the year in the transition zone even though soils contain sufficient levels of this trace element. In this study, 'Penncross' creeping bentgrass was grown in an environmental growth chamber in a factorial arrangement of three chelated Fe rates (iron diethylenetriamine pentaacetate, FeDTPA), two N levels, and three irrigation regimes. Turf was preconditioned to soil moisture stress by allowing soil moisture levels to dry to either 80,50, or 20% of the total unsaturated soil moisture (TUSM) before being irrigated to 100% TUSM. Ambient temperatures and photoperiods within the chamber were altered to simulate a late fall through mid‐summer growth cycle. Foliar applications of FeDTPA increased top growth during cool temperatures, but as temperatures were raised, FeDTPA applications depressed top growth. Net photosynthesis (NP) was also reduced by FeDTPA; however, dark respiration was unchanged. Foliar carbohydrates were increased with FeDTPA and appeared directly related to corresponding top growth reductions. Moisture stress preconditioning did not significantly influence plant response to applications of FeDTPA. However, repeated exposure to low soil moisture tended to reduce foilage yields and increase verdure. This indicated a more decumbent growth habit had resulted from repeated moisture stress. Net photosynthesis decreased as soil moisture levels declined. However, preconditioning turf to low soil moisture did not subsequently influence NP at either low or high soil moisture levels. Dark respiration (DR), was significantly lower for plants previously grown at the lowest irrigation regime regardless of subsequent soil moisture level. This reduction in DR may help account for the increased foliar carbohydrates associated with infrequent irrigation. This study did not show that turf response to FeDTPA was related to interactions with moisture stress. However, turf did adapt both morphologically and physiologically to repeated cycles of low soil moisture.

EFFECTS OF AMMONIUM AND NITRATE NUTRITION ON THE OSTRICH FERN (Matteuccia struthiopteris)

Plants were grown in controlled environments at 24/18 °C or 18/12 °C light/dark temperatures with 8, 16 or 32 meq/L nitrate or ammonium concentrations in a complete nutrient solution applied twice weekly to perlite rooting medium. Frond length was not affected by any of the treatments. Ammonium nutrition, compared with nitrate, reduced frond fresh and dry weights, water use, frond water potential, frond diffusive conductance and foliar concentrations of Ca and carbohydrates. Ammonium N increased the foliar concentration of inorganic NH4+, organic N, total N, P, K, and Mn. Increasing N concentration in the nutrient solution had no significant effect on dry weight, but increased foliar concentrations of N (inorganic and organic) and decreased fresh weight, fronds per plant, water use, frond diffusive conductance and foliar concentrations of Mn. The higher temperature decreased frond dry weight and foliar carbohydrate concentrations but increased frond number in the first emergence and foliar concentrations of several nutrients.