A normal appearing plant with a low rate of photorespiration (ratio of (14)CO(2) released light/dark = 1.6) was found in an unselected tobacco (Nicotiana tabacum) cultivar. The plant was self-pollinated, and further selections were made on several successive generations. Excised leaves from the progeny of the selections were examined for photorespiration and net CO(2) assimilation in normal air...

Measurements of gross photosynthesis; respiration, rate of net oxygen diffusion, and organic storage are reported for 7 microcosms maintained over periods of 5 to 7 months. Average rates of gross photosynthesis ranged from 0.86 to 1.69 g Oz/m2/day and were related to the amounts of inorganic nutrients added. Average final organic storage was equal to 35.6% of gross photosynthesis. Assumed photo...

Individual groups of peach (Prunus persica [L.] Batsch) seedlings stressed to -17, -26 and -36 bars recovered to control levels within 1, 3, and 4 days, respectively. Stomatal resistance was significantly correlated with both leaf water potential and net photosynthesis. In seedlings stressed to -52 bars, leaf water potential and stomatal resistance recovered sooner than net photosynthesis, desp...

open ocean ecosystems. Geochemical approaches indicate that the oceans are net positive autotrophic, but direct observations based on short-term incubation techniques suggest that the ocean is in a state of net heterotrophy. One hypothesis for the apparent discrepancy is that net autotrophic production occurs in aperiodic ‘‘bursts,’’ which are superimposed on a more constant background state of...

Understory red spruce (Picea rubens Sarg.) trees, between 20 and 50 cm in height and 12 years or more in age, were collected from mid- and high-elevation stands in north-central Vermont and placed in a closed-cuvette system to measure photosynthetic and transpirational responses to photosynthetic photon flux density (PPFD) and temperature. Photosynthesis, dark respiration, transpiration and wat...

Increasing pretreatment day temperatures of 20, 30, and 40 C resulted in decreased net photosynthesis in Agropyron smithii (C(3)) while in Bouteloua gracilis (C(4)) net photosynthesis was increased. The effect on photosynthesis of increasing analysis temperatures was the same as observed by increasing pretreatment temperatures. Resistance of the stomata and boundary layer were less affected by ...

Net photosynthesis is stimulated in third seedling leaves of barley plants whose lower two leaves are heavily infected by Erysiphe graminis f.sp. hordei Marchal. Stimulation is greater in water-stressed than in well-watered plants. In stressed, but not in well-watered plants, stimulation is associated with the maintenance of high leaf water potential and high leaf conductance. A small part of t...

Plants with citrus variegated chlorosis (CVC), a disease caused by the xylem-limited bacteria Xylella fastidiosa, have leaves with water deficiency symptoms and are associated with decreases on the net photosynthesis and transpiration rates. Using healthy and CVC-affected ‘Pêra’ sweet orange plants on ‘Rangpur’ lime rootstock, the leaf gas exchange variables were measured with an open-gas porta...

We investigated the effect of intraspecific competition on growth parameters and photosynthesis of the salt marsh species Atriplex prostrata Boucher in order to distinguish the effects of densitydependent growth inhibition from salt stress. High plant density caused a reduction of 30% in height, 82% in stem dry mass, 80% in leaf dry mass, and 95% in root dry mass. High density also induced a pr...

The photocontrol of the functional coupling between photosynthesis and stomatal conductance in the leaf was investigated in gas exchange experiments using monochromatic light provided by lasers. Net photosynthesis and stomatal conductance were measured in attached leaves of Malva parviflora L. as a function of photon irradiance at 457.9 and 640.0 nanometers.Photosynthetic rates and quantum yiel...