scholarly journals Photosynthesis of Tropical Pasture Plants I. Illuminance, Carbon Dioxide Concentration, Leaf Temperature, and Leaf-Air Vapour Pressure Difference

1971 ◽  
Vol 24 (3) ◽  
pp. 449 ◽  
Author(s):  
M M Ludlow ◽  
GL Wilson
Keyword(s):  
Carbon Dioxide ◽  
Vapour Pressure ◽  
Pressure Difference ◽  
Carbon Dioxide Concentration ◽  
Gas Analysis ◽  
Leaf Temperature ◽  
Tropical Pasture ◽  
Analysis System ◽  
Vapour Pressure Difference ◽  
Pasture Plants

Carbon dioxide and water vapour exchange of attached, young, fully expanded leaves of tropical pasture species were measured in an open gas analysis system. The influence of illuminance, carbon dioxide concentration, leaf temperature, and leaf-air vapour pressure difference on net photosynthetic rate and carbon dioxide transfer resistances was studied.

scholarly journals Photosynthesis of Tropical Pasture Plants II. Temperature and Illuminance History

1971 ◽  
Vol 24 (4) ◽  
pp. 1065 ◽  
Author(s):  
MM Ludlow ◽  
GL Wilson
Keyword(s):  
Carbon Dioxide ◽  
Water Vapour ◽  
Gas Analysis ◽  
Controlled Environment ◽  
Tropical Pasture ◽  
Two Temperatures ◽  
Analysis System ◽  
Pasture Plants

Grasses and legumes were grown at two temperatures in controlled-environment rooms and at three illuminances (obtained by shading) in a glasshouse. Carbon dioxide and water vapour exchange of leaves were measured in an open gas analysis system.

scholarly journals Photosynthesis of Tropical Pasture Plants III. Leaf Age

1971 ◽  
Vol 24 (4) ◽  
pp. 1077 ◽  
Author(s):  
MM Ludlow ◽  
GL Wilson
Keyword(s):  
Dark Respiration ◽  
Leaf Age ◽  
Gas Analysis ◽  
Controlled Environment ◽  
Tropical Pasture ◽  
Optimum Conditions ◽  
Dark Respiration Rate ◽  
Leaf Ontogeny ◽  
Analysis System ◽  
Pasture Plants

Grass and legume plants were grown under near-optimum conditions in controlled-environment cabinets. Changes in net photosynthetic rate, dark respiration rate, and carbon dioxide transfer resistances during leaf ontogeny, and variability between leaves on grass tillers and legume runners were studied under controlled conditions in an open gas analysis system.

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.

Leaf anatomical adaptations have central roles in photosynthetic acclimation to humidity

2019 ◽  
Vol 70 (18) ◽  
pp. 4949-4962 ◽  
Author(s):  
Qingjie Du ◽  
Tao Liu ◽  
Xiaocong Jiao ◽  
Xiaoming Song ◽  
Jiayu Zhang ◽  
...  
Keyword(s):  
Cell Size ◽  
Vapour Pressure ◽  
Pressure Difference ◽  
Mesophyll Cell ◽  
Photosynthetic Acclimation ◽  
Anatomical Adaptations ◽  
Tomato Cultivars ◽  
Vapour Pressure Difference

Examination of long-term photosynthetic acclimation of two tomato cultivars (Jinpeng and Zhongza) to leaf-to-air vapour pressure difference reveals that independent changes in epidermal and mesophyll cell size maintain photosynthetic homeostasis in Jinpeng.

scholarly journals Effect of Light Intensity and Leaf Temperature on Photosynthesis and Transpiration in Wheat and Sorghum

1970 ◽  
Vol 23 (4) ◽  
pp. 775 ◽  
Author(s):  
RW Downes
Keyword(s):  
Carbon Dioxide ◽  
Water Use ◽  
Carbon Dioxide Concentration ◽  
Leaf Temperature ◽  
High Light ◽  
Intercellular Spaces ◽  
Concentration Difference ◽  
Light Levels ◽  
Light Intensities ◽  
Water Vapour Concentration

Wheat stomata offered less resistance to water and carbon dioxide diffusion than sorghum stomata at light intensities of 0�06 and 0�26 cal cm-2 min-i (400-700 nm) but resistances were comparable at 0�46 cal cm-2 min-i. Consequently, transpiration rates were higher in wheat than in sorghum, except at the high light levels, in leaf chamber experiments described here. Rates of photosynthesis were higher in sorghum than in wheat, with the greatest difference at high light levels. This resulted in a greater efficiency of dry matter production relative to water use in sorghum. Transpiration rate increased with increased temperature in both species. Photosynthesis was independent of temperature in wheat, and in sorghum under low light conditions, but otherwise photosynthesis increased with temperature in sorghum. In both species, efficiency of water use decreased as temperature increased at all light intensities. Water vapour concentration difference between the intercellular spaces and the air was comparable in wheat and sorghum and increased with temperature. The carbon dioxide concentration difference between air and intercellular spaces was substantially greater in sorghum than in wheat and increased with leaf temperature. Maximum values were obtained at the intermediate light level in sorghum.

The growth and development of cowpeas (Vigna unguiculata) under tropical field conditions

1981 ◽  
Vol 97 (3) ◽  
pp. 539-550 ◽  
Author(s):  
E. J. Littleton ◽  
M. D. Dennett ◽  
J. Elston ◽  
J. L. Monteith
Keyword(s):  
Exchange Rate ◽  
Growth And Development ◽  
Water Shortage ◽  
Gas Analysis ◽  
Leaf Temperature ◽  
Maximum Efficiency ◽  
Light Saturation ◽  
Infra Red ◽  
Analysis System ◽  
Ibadan Nigeria

SUMMARYThe CO2 exchange of leaves, pods and peduncles was measured in cowpea crops grown at Ibadan, Nigeria, using a portable infra-red gas analysis system. Most leaves had maximum rates of photosynthesis (Pm) of about 1·4 mg CO2/m2/sec and maintained this value for 20 days from full expansion. Early leaves had slightly slower rates. Pm decreased when leaf temperature exceeded 35 °C. The maximum efficiency of photosynthesis, ɛm, was about 2 g CO2/E (0·045 mol CO2/E). ɛmdecreased with temperature for leaves, but increased for pods. The latter response probably results from the effect of the high CO2 concentrations within the pod on the ribulose disphosphate carboxylation reaction. Water shortage reduced Pm but not ɛm. Pods and peduncles had a slightly negative CO2 exchange rate at light saturation but this was considerably less than the rate of CO2 evolution in the dark.

scholarly journals Influence of season, drought and xylem ABA on stomatal responses to leaf-to-air vapour pressure difference of trees of the Australian wet-dry tropics

2000 ◽  
Vol 48 (2) ◽  
pp. 143 ◽  
Author(s):  
D. S. Thomas ◽  
D. Eamus ◽  
S. Shanahan
Keyword(s):  
Stomatal Conductance ◽  
Vapour Pressure ◽  
Pressure Difference ◽  
Dry Season ◽  
Wet Season ◽  
Stomatal Responses ◽  
Dry Seasons ◽  
Stomatal Sensitivity ◽  
Vapour Pressure Difference ◽  
Wet And Dry Seasons

This paper reports the results of two experiments undertaken to investigate the influence of season and soil drying on stomatal responses to leaf-to-air vapour pressure differences. We examined the response of stomatal conductance to increasing leaf-to-air vapour pressure difference, in the wet and dry seasons, of five tropical tree species. We also examined leaves of these species for anatomical differences to determine whether this could explain differences in stomatal sensitivity to leaf-to-air vapour pressure differences. Finally, we conducted a split-root experiment with one of those species to look for interactions between xylem abscisic acid concentration, predawn water potential, leaf area to root mass ratio and stomatal responses to leaf-to-air vapour pressure differences. Stomatal conductance declined linearly with increasing leaf-to-air vapour pressure difference in all species. Leaves that expanded in the ‘dry’ season were more sensitive to leaf-to-air vapour pressure differences than those that had expanded in the ‘wet’ season. The value of leaf-to-air vapour pressure difference where 50% of extrapolated maximum stomatal conductance would occur was 5.5 kPa for wet season but only 3.4 kPa for dry season leaves. In the wet season, transpiration rate increased with increasing leaf-to-air vapour pressure difference in most example species. However, in the dry season, transpiration was constant as leaf-to-air vapour pressure differences increased in most cases. There were significant changes in the proportion of cell wall exposed to air space in leaves, between wet and dry seasons, in three of four species examined. In the split-root experiment, a very mild water stress increased stomatal sensitivity to leaf-to-air vapour pressure differences, and stomatal conductivity declined linearly with decreasing predawn water potential. However, levels of ABA in the xylem did not change, and stomatal sensitivity to exogenous ABA did not change. The ratio of leaf area to root mass declined during water stress and was correlated to changes in stomatal sensitivity to leaf-to-air vapour pressure differences.

scholarly journals The Croonian Lecture - Transport of substances in plants

1938 ◽  
Vol 125 (838) ◽  
pp. 1-25 ◽  
Keyword(s):  
Vapour Pressure ◽  
Pressure Difference ◽  
Royal Society ◽  
Driving Force ◽  
Energy Conditions ◽  
First Approximation ◽  
Vapour Pressure Difference

When the Royal Society—now many years ago—did the late Dr Joly and me the honour of publishing our first paper on the ascent of sap (Dixon and Joly 1894, 1895), it was not difficult to make a first approximation as to the mechanism, and the energy conditions, availed of by plants in lifting water from the soil to their leaves. The driving force was to be sought in the vapour-pressure difference obtaining in the spaces surrounding the roots and the leaves (Dixon 1897).

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