scholarly journals Effects of Vapour Pressure Difference on CO_2 Assimilation Rate, Leaf Conductance and Water Use Efficiency in Grass Species

10.5109/23831 ◽  
1987 ◽  
Vol 31 (1/2) ◽  
pp. 1-10
Author(s):  
Yoshinobu Kawamitsu ◽  
Waichi Agata ◽  
Shigenori Miura
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Vapour Pressure ◽  
Pressure Difference ◽  
Leaf Conductance ◽  
Grass Species ◽  
Assimilation Rate ◽  
Use Efficiency ◽  
Vapour Pressure Difference

Response of wheat growth and CO2 assimilation to altering root-zone temperature

1990 ◽  
Vol 68 (12) ◽  
pp. 2698-2702 ◽  
Author(s):  
S. H. Al-Hamdani ◽  
G. W. Todd ◽  
D. A. Francko
Keyword(s):  
Water Use Efficiency ◽  
Water Potential ◽  
Water Use ◽  
Root Zone ◽  
Soluble Sugar ◽  
Leaf Conductance ◽  
Assimilation Rate ◽  
Root Zone Temperature ◽  
Use Efficiency ◽  
Zone Temperature

Wheat plants (Triticum aestivum L. var. Chisholm) grown at an air temperature of 23 °C and a root-zone temperature of 3 °C exhibited a significant reduction in shoot and root dry weight and leaf area compared with plants grown at a root-zone temperature of 23 °C. This reduction was correlated with a significantly lower CO2 assimilation rate that was associated with lower leaf conductance, lower internal CO2 concentration, and more negative water potential. Low CO2 assimilation rate was also associated with high starch and total soluble sugar levels in the shoot, less translocation of photosynthate, and possibly less sink demand. Leaf chlorophyll concentration was not affected by altering the root-zone temperature, whereas water use efficiency of plants grown at a root-zone temperature of 3 °C was as much as 1.5 times higher as those grown at 23 °C. Key words: carbohydrate, chlorophyll, photosynthate partitioning, leaf conductance, water potential, water use efficiency.

Photosynthesis and Transpiration of Pinus Radiata D. Don Under Plantation Conditions in Southern Australia. Ii. First-Year Seedlings and 5-Year-Old Trees on Aeolian Sands at Rennick (South-Western Victoria).

1982 ◽  
Vol 9 (6) ◽  
pp. 761 ◽  
Author(s):  
PM Attiwill ◽  
RO Squire ◽  
TF Neales
Keyword(s):  
Pinus Radiata ◽  
Vapour Pressure ◽  
Pressure Difference ◽  
Net Photosynthesis ◽  
Co2 Assimilation ◽  
First Year ◽  
Assimilation Rate ◽  
Old Trees ◽  
Vapour Pressure Difference ◽  
Very High

Measurements of net CO2 assimilation and transpiration rates were made over 4 days in the field in February 1980, on first-year seedlings and 5-year-old trees of Pinus radiata growing in plantation conditions in SW. Victoria. Gas exchange, enclosure, methods were used. Very high needle temperatures (to 45�C) and vapour pressure differences (to 70 mbar) were encountered. Watering treatments allowed estimates to be made of the effect of existing soil water deficits. The maximum rates of assimilation observed were 3.78 �mol CO2 m-� s-� in the watered seedlings and 3.15 �mol m-� s-� in the unwatered tree. These values are 40% less than has been recently reported for P. radiata in New Zealand but agree with other data for P. radiata and other conifers. The light saturation of net photosynthesis occurred at c. 350 W m-�. Increase in needle-air vapour pressure difference reduced needle conductance. Decrease of needle temperature and of vapour pressure difference from very high values, due to a rapid drop in air temperature, was accompanied by an increase of assimilation rate and of needle conductance, confirming that needle temperatures above about 30�C are supraoptimal for P. radiata. Watering increased assimilation rate, needle water potential and needle conductance. This was most apparent in the seedlings; the responses of the older trees were much less marked.

Diurnal Time Course of Leaf Gas Exchange Rates and Related Characters in Drought-Acclimated and Irrigated Trifolium Subterraneum.

1995 ◽  
Vol 22 (3) ◽  
pp. 461 ◽  
Author(s):  
J Vadell ◽  
C Cabot ◽  
H Medrano
Keyword(s):  
Gas Exchange ◽  
Exchange Rates ◽  
Water Use Efficiency ◽  
Water Use ◽  
Leaf Gas Exchange ◽  
Trifolium Subterraneum ◽  
Co2 Assimilation ◽  
Carbon Gain ◽  
Assimilation Rate ◽  
Use Efficiency

The effects of drought acclimation on the diurnal time courses of photosynthesis and related characters were studied in Trifolium subterraneum L. leaves during two consecutive late spring days. Leaf CO2 assimilation rate and transpiration rate followed irradiance variations in irrigated plants. Under drought, a bimodal pattern of leaf CO2 assimilation rate developed although stomatal conductance remained uniform and low. Instantaneous water-use efficiency was much higher in droughted plants during the early morning and late evening, while during the middle of the day it was close to the value of irrigated plants. Net carbon gain in plants under drought reached 40% of the carbon gain in irrigated plants with a significant saving of water (80%). Average data derived from midday values of leaf CO2 assimilation rates and instantaneous water-use efficiency did not provide good estimates of the daily carbon gain and water-use efficiency for droughted leaves. Coupled with the morphological changes as a result of acclimation to progressive drought, modifications of diurnal patterns of leaf gas exchange rates effectively contribute to a sustained carbon gain during drought. These modifications significantly improve water-use efficiency, mainly by enabling the plant to take advantage of morning and evening hours with high air humidity.

Microhabitat comparisons of transpiration and photosynthesis in three subalpine conifers

1988 ◽  
Vol 66 (5) ◽  
pp. 963-969 ◽  
Author(s):  
Gregory A. Carter ◽  
William K. Smith
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Pinus Contorta ◽  
Photosynthetic Performance ◽  
Leaf Conductance ◽  
Forest Understory ◽  
Subalpine Forest ◽  
Abies Lasiocarpa ◽  
Use Efficiency ◽  
Central Rocky Mountains

Differences in water and photosynthetic relations were compared for three codominant conifers (Engelmann spruce (Picea engelmaniï), subalpine fir (Abies lasiocarpa), and lodgepole pine (Pinus contorta) at microhabitats within a subalpine forest (central Rocky Mountains, U.S.A.) that were considered representative of different successional stages. Diumal measurements of photosynthesis, leaf conductance, and transpiration were taken at microhabitats considered early-successional (open), intermediate (forest gap), and late-successional (forest understory) environments to evaluate possible influences of gas-exchange physiology in observed distributional and successional patterns. Pine had greater water-use efficiency (photosynthesis/transpiration) in early- versus late-successional environments, primarily as a result of a lower leaf conductance and transpiration. Photosynthetic performance was similar among all three species at each respective microhabitat and increased as the openness of the microhabitat increased. Greater water-use efficiency may significantly improve the growth of pine over spruce and fir on more open, drier sites at lower elevation. Higher transpiration in spruce and fir may limit these species to higher elevation sites, to understory sites at middle elevations, and to moister open sites at lower elevations (e.g., riparian sites).

scholarly journals PHOTOSYNTHESIS AND TRANSPIRATION DURING GROWTH AND DEVELOPMENT OF ALLIUM CEPA L.

HortScience ◽  
1993 ◽  
Vol 28 (4) ◽  
pp. 263B-263
Author(s):  
Daniel Warnock ◽  
William Randle ◽  
Mark Rieger
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Allium Cepa ◽  
Growth And Development ◽  
Developmental Stages ◽  
Leaf Conductance ◽  
Short Day ◽  
Allium Cepa L ◽  
Use Efficiency ◽  
Inductive Photoperiod

Photosynthesis is the very essence of agriculture. Previous photosynthetic and transpirational studies of onion (Allium cepa) have been limited to specific developmental stages. Our study measured photosynthesis and transpiration in sixteen plants of a single short-day cultivar over an eleven week period containing both non- and bulb inductive photoperiods. Differences in weekly means for photosynthesis, leaf conductance, water use efficiency, and intercellular CO, were highly significant. Weekly photosynthetic means increased under a non-inductive photoperiod and peaked one week after initiating a bulb inducing photoperiod. A decrease and leveling period occurred as bulbs developed followed by a decrease as foliage lodged. Weekly photosynthetic and leaf conductance means were correlated and highly significant. Water use efficiency and intercellular CO, means remained fairly constant throughout the study suggesting that photosynthesis in unstressed onions was controlled by internal mechanisms instead of stomata.

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