Changes in net photosynthesis, transpiration and dark respiration in winter barley exposed to elevated levels of sulphur dioxide using an open-air fumigation system

Population differentiation in Tsuga canadensis (L.) Carr. from Wisconsin was tested by comparing seedlings grown from seed collected within the present range in the northeast and from seed collected in disjunct populations southwest of the present range. The seedlings, established in hydroponic culture, were subjected to two preconditioning temperature regimes and two water stress simulations. Net photosynthesis, dark respiration, and transpiration capacities were measured and internal leaf resistances were calculated.The southwestern Wisconsin population had a more favorable carbon dioxide balance at warmer tissue temperatures, particularly at low irradiance levels, and at higher osmotic potentials, than did the northeastern population, which was better adapted to lower tissue temperatures and lower osmotic potentials. Additional differences between seed sources in seedling morphology, transpiration rate, and water-use efficiency were found. These differences in morphology and physiological responses corresponded to the macroclimates in which these populations were found, southwestern Wisconsin being warmer and drier than the northeastern part of the state.

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Productivity of Vegetable Crops in a Region of High Solar Input. III. Carbon Balance of Potato Crops

Functional Plant Biology ◽

10.1071/pp9740283 ◽

1974 ◽

Vol 1 (2) ◽

pp. 283 ◽

Cited By ~ 26

Author(s):

PJM Sale

Keyword(s):

Carbon Balance ◽

Dark Respiration ◽

Net Photosynthesis ◽

Dry Weight ◽

Gas Analysis ◽

Co2 Uptake ◽

Co2 Efflux ◽

Vegetable Crops ◽

Weight Changes ◽

Potato Crops

The carbon balance of potato crops has been studied by measuring canopy net photosynthesis and dark respiration losses with a field assimilation chamber and semi-closed gas analysis system. Results are given for the latter part of growth in both a spring-planted and a summer-planted crop. Net CO2 uptake increased with solar input to reach 35–40mg dm-2 (ground area) h-1 at 400–450 W m-2, but light saturation then occurred and little or no further uptake resulted from increases in solar input up to 1000 W m-2. This supports the previous conclusion that net photosynthesis in the potato is determined by the size of the 'sink' provided by the developing tubers. The imposed experimental variables of reduced solar input (21 and 34% shade) and soil moisture were found not to affect the relation between solar input and CO2 uptake, and the effect of chamber temperature was also very small. Dark respiration rates of the canopy were markedly sensitive to temperature, and also to the solar input prior to measurement. Respiration from the below-ground plant parts accounted for a considerable part of the total plant respiration. In all, 15–20 % of the net assimilation during daylight hours was lost by night respiration. There was little variation in CO2 efflux from uncropped soil during the experiments. Dry weight changes calculated from the gasometric measurements were in accordance with those found from previous growth analysis. * Part II, Aust. J. Agric. Res., 1973, 24, 751–62.

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Response of Gas Exchange in Jointed Goatgrass (Aegilops cylindrica) to Environmental Conditions

Weed Science ◽

10.1017/s0043174500072416 ◽

1989 ◽

Vol 37 (4) ◽

pp. 562-569 ◽

Cited By ~ 3

Author(s):

David R. Gealy

Keyword(s):

Soil Moisture ◽

Gas Exchange ◽

Environmental Conditions ◽

Dark Respiration ◽

Net Photosynthesis ◽

Soil Matric Potential ◽

Dark Respiration Rate ◽

Matric Potential ◽

Aegilops Cylindrica ◽

Jointed Goatgrass

Gas exchange of jointed goatgrass leaves was affected by temperature, irradiance level, and soil matric potential. Net photosynthesis of leaves under saturating irradiance (PPFD3= 1850 (μE·m–2·s−1) was optimum at about 20 C. At 25 C, net photosynthesis was nearly 90% of maximum at a PPFD of 800 μE·m–2·−1. Transpiration, and presumably water use, increased steadily with temperature from 10 to 40 C. Dark respiration rate and compensation points for light and for CO2increased exponentially, or nearly so, from 10 to 40 C. Soil moisture deficits of −130 kPa reduced net photosynthesis and transpiration by about 30 and 55%, respectively, compared to well-watered plants.

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