A three-phase discontinuous sucrose gradient yielded two fractions of chloroplast envelope membranes from spinach (Spinacia oleracea L.), sunflower (Helianthus annuus L.), and maize (Zea mays L., mesophyll and undifferentiated chloroplasts). These species were selected to represent plants with fast photorespiration and slow net photosynthesis, fast photorespiration yet fast net photosynthesis, ...

Gas exchange, tissue water relations, and leaf/root dry weight ratios were compared among young, container-grown plants of five temperate-zone, deciduous tree species (Acer negundo L., Betula papyrifera Marsh, Malus baccata Borkh, Robinia pseudoacacia L., and Ulmus parvifolia Jacq.) under well-watered and water-stressed conditions. There was a small decrease (mean reduction of 0.22 MPa across s...

Seedlings of Taxodium distichum L., Quercus lyrata Walt. and Q. falcata var. pagodaefolia Ell. were grown for 22 days in a rhizotron system providing two soil redox potential regimes, +170 mV (low Eh) and +560 mV (high Eh). Leaf chlorophyll concentration and gas exchange, root alcohol dehydrogenase (ADH) activity, root and leaf ethylene production, and growth and biomass partitioning were measu...

the two-spotted spider mite, tetranychus urticae koch (acari: tetranychidae) is one of the most important agricultural pests of the world. it causes direct and indirect damage on plants which decreases in photosynthesis and crop yield. the effect of sublethal concentrations of artemisia annua l. (asteraceae) and rosmarinus officinalis l. (lamiaceae) essential oils were assessed on development a...

terminal drought stress during grain filling period has recently become more common in the semiarid mediterranean regions, where wheat (triticum aestivum) is grown as an important winter cereal crop. the objective of this experiment was to study the effect of terminal drought stress on grain yield, gas exchange variables, and some physiological traits of nine bread wheat cultivars. an experimen...

The addition of glyoxylate to tobacco (Nicotiana tabacum) leaf discs inhibited glycolate synthesis and photorespiration and increased net photosynthetic (14)CO(2) fixation. This inhibition of photorespiration was investigated further by studying the effect of glyoxylate on the stimulation of photosynthesis that occurs when the atmospheric O(2) level was decreased from 21 to 3% (the Warburg effe...

In C4 plants, carbonic anhydrase (CA) facilitates both the chemical and isotopic equilibration of atmospheric CO2 and bicarbonate (HCO3-) in the mesophyll cytoplasm. The CA-catalyzed reaction is essential for C4 photosynthesis, and the model of carbon isotope discrimination (Delta13C) in C4 plants predicts that changes in CA activity will influence Delta13C. However, experimentally, the influen...

Foliar ozone uptake rates of different-sized black cherry (Prunus serotina Ehrh.) trees were compared within a deciduous forest and adjacent openings in north-central Pennsylvania during one growing season. Study trees included open-grown seedlings and saplings, forest understory seedlings and saplings, and sunlit and shaded portions of mature canopy tree crowns. Instantaneous ozone uptake rate...

Greenhouse-grown plants of Xanthium strumarium L. were exposed in a growth cabinet to 10 C during days and 5 C during nights for periods of up to 120 hours. Subsequently, CO(2) exchange, transpiration, and leaf temperature were measured on attached leaves and in leaf sections at 25 or 30 C, 19 C dew point of the air, 61 milliwatts per square centimeter irradiance, and CO(2) concentrations betwe...

Laboratory expenments were conducted to evaluate the effects of increased so11 salinity on gas exchange functlonlng and growth of the braclush-marsh grass Spartlna patens (Alt) Muhl under controlled soil redox potentials (Eh) which were malntalned at either aerobic (+489 mV) or hypoxlc (-40 mV) conditions Plants were subjected to salinities of 0 5, 15 and 25 ppt gradually over a 7 d penod and l...