Photosynthetic gas exchange and water use in tropical and subtropical populations of the mangrove Aegiceras corniculatum

1998 ◽  
Vol 49 (4) ◽  
pp. 329 ◽  
Author(s):  
Tarek Youssef ◽  
Peter Saenger
Keyword(s):  
Gas Exchange ◽  
Water Use ◽  
Vapour Pressure Deficit ◽  
Photosynthetic Gas Exchange ◽  
Aegiceras Corniculatum ◽  
Stomatal Behaviour ◽  
Arid Conditions ◽  
Air Temperatures ◽  
Quantum Flux ◽  
Use Efficiency

Photosynthetic gas exchange and stomatal behaviour in the tropical (Darwin: 12°25′S) and subtropical (Ballina: 28°50′S) populations of the mangrove Aegiceras corniculatum (L.) Blanco were compared at elevated air temperatures (>32°C) and leaf-to-air vapour pressure deficit (vpd >25 mbar) with a quantum flux at, or above, their light saturation capacity (>600 µmol m-2 s-1). At the lower end of the tested aridity range, the tropical population showed a less conservative water use than the subtropical population. As aridity increased, both populations showed a reduction in stomatal conductance. However, transpiration rates remained higher in the subtropical population at all times, reducing its water-use efficiency from that under less arid conditions. At extreme aridity (temperature >37°C and vpd >35 mbar), the efficiency of the evaporative cooling of fully exposed leaves was evident in the leaf-to-air temperature differential which remained minimal in the tropical population while it increased significantly in the subtropical population. Aridity tolerance was more pronounced in individuals from the tropical site than from the subtropical site, as evidenced by a tighter stomatal control on water use in the tropical population. These data suggest that the tropical and subtropical populations of A. corniculatum have different physiological responses to aridity.

Physiological acclimation of Pinus flexilis to drought stress on contrasting slope aspects in Waterton Lakes National Park, Alberta, Canada

2009 ◽  
Vol 39 (3) ◽  
pp. 629-641 ◽  
Author(s):  
Matthew G. Letts ◽  
Kevin N. Nakonechny ◽  
K. Eric Van Gaalen ◽  
Cyndi M. Smith
Keyword(s):  
Gas Exchange ◽  
Water Use ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Vapour Pressure Deficit ◽  
Net Photosynthesis ◽  
Pinus Flexilis ◽  
Limber Pine ◽  
Use Efficiency ◽  
Physiological Acclimation

Photosynthetic gas-exchange characteristics were measured in Pinus flexilis James (limber pine) during two drought years in a xeric, subalpine ecosystem of the Rocky Mountains. Limber pine exhibited conservative water-use traits, including low specific leaf area, leaf nitrogen, stomatal conductance, transpiration (E), and light-saturated net photosynthesis (Amax), but exhibited high needle longevity, water-use efficiency (Amax/E), and stable carbon isotope composition. Net photosynthesis declined strongly with leaf-to-air vapour pressure deficit, resulting in a bimodal seasonal pattern of Amax. Although very little gas exchange was observed in late summer, photosynthetic activity extended into October. The avoidance of gas exchange during high atmospheric demand maximized whole-season water-use efficiency. Leaf temperature and leaf-to-air vapour pressure deficit were higher on south-facing slopes during both moderate (2006) and severe (2007) drought. Severe drought caused lower stomatal conductance and E on the southeast-facing slope, but neither Amax nor canopy reflectance indices differed among slope aspects. Although Amax was lower in 2007 than 2006, branch-length increment did not differ. Foliar stable carbon isotope composition was higher in needles produced in dry years but did not vary among slope aspects. These results indicate that physiological acclimation to water stress prevented among-aspect differences in Amax and that shoulder-season photosynthesis may become increasingly important in a warmer climate.

Seasonal photosynthetic gas exchange and water-use efficiency in a constitutive CAM plant, the giant saguaro cactus (Carnegiea gigantea)

Oecologia ◽  
2011 ◽  
Vol 167 (3) ◽  
pp. 861-871 ◽  
Author(s):  
Dustin R. Bronson ◽  
Nathan B. English ◽  
David L. Dettman ◽  
David G. Williams
Keyword(s):  
Gas Exchange ◽  
Water Use Efficiency ◽  
Water Use ◽  
Photosynthetic Gas Exchange ◽  
Carnegiea Gigantea ◽  
Use Efficiency ◽  
Cam Plant

Carbon Production of Sunflower Cultivars in Field and Controlled Environments. I. Photosynthesis and Transpiration of Leaves, Stems and Heads

1980 ◽  
Vol 7 (5) ◽  
pp. 555 ◽  
Author(s):  
HM Rawson ◽  
GA Constable
Keyword(s):  
Gas Exchange ◽  
Water Use Efficiency ◽  
Leaf Area ◽  
Water Use ◽  
Leaf Age ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Supplementary Irrigation ◽  
Quantum Flux ◽  
Use Efficiency

Commercial cultivars of sunflower were grown either with adequate water in glasshouses, or in the field using stored moisture or with supplementary irrigation. Diurnal measurements of photosynthesis, transpiration, respiration and water use efficiency were made as leaves expanded and aged: several leaf positions of each cultivar and treatment were examined throughout the season. Responses to quantum flux density were also determined. Comparable treatments in the field and glasshouse gave similar results and any differences in gas exchange per unit leaf area among cultivars were very small. All leaves, regardless of position on the plant had the same age-determined pattern of gas exchange per unit leaf area. Rates peaked some 10-12 days after leaves were 5 cm2 and had fallen to 50% of these values 50 days later: the decline was slightly faster in field canopies. Instantaneous rates of photosynthesis were occasionally reduced in plants growing on stored moisture when leaf water potential fell below 1.0 MPa, but on a diurnal scale these reductions were small. Water use efficiency declined with leaf age though under saturating light the decline was only 13% in 60 days: efficiency was markedly reduced at quantum flux densities below 800 �E m-2 s-1. The contribution of heads and stems to photosynthesis and transpiration throughout grain growth is discussed. It is concluded that the water use efficiency of sunflower in the short term is similar to that of other C3 species in spite of the high rates of gas exchange of sunflower. On a diurnal basis, its characteristic of maintaining open stomata under conditions of high evaporative demand results in poor water economy. Sunflower appears to be set to maximize carbon fixation per unit leaf area almost regardless of conditions.

scholarly journals Association of carbon isotope discrimination with leaf gas exchange and water use efficiency in maize following soil amendment with superabsorbent hydrogel

2018 ◽  
Vol 64 (No. 10) ◽  
pp. 484-490
Author(s):  
Yang Wei ◽  
Li Pin-Fang
Keyword(s):  
Gas Exchange ◽  
Water Use Efficiency ◽  
Carbon Isotope ◽  
Water Use ◽  
Carbon Isotope Discrimination ◽  
Photosynthetic Gas Exchange ◽  
Superabsorbent Hydrogel ◽  
Isotope Discrimination ◽  
Intrinsic Water Use Efficiency ◽  
Use Efficiency

The correlation of carbon isotope discrimination (△<sup>13</sup>C) with photosynthetic gas exchange and water use efficiency (WUE) in maize was investigated under low rainfall conditions with or without superabsorbent polymer (SAP). SAP (45 kg/ha) was mixed into the top 10 cm soil layer at sowing in lysimeters. Compared with the control plants not treated with SAP, the application of SAP increased net photosynthesis rate; stomatal conductance (g<sub>s</sub>); transpiration rate; chlorophyll content (Chl) and intrinsic water use efficiency at leaf level (WUE<sub>i</sub>), but decreased intercellular CO<sub>2</sub> concentration (C<sub>i</sub>) and leaf △<sup>13</sup>C. In plants supplied with SAP, leaf △<sup>13</sup>C was positively correlated with C<sub>i</sub> (r = 0.864, P &lt; 0.01) and negatively correlated with g<sub>s</sub> and WUE<sub>i</sub> (r = –0.860 and –0.626, P &lt; 0.01, respectively). Leaf △<sup>13</sup>C was not correlated with Chl with or without SAP. Grain △<sup>13</sup>C significantly decreased by 12.4% and showed a significant negative correlation with grain WUE under SAP treatments (r = –0.670, P &lt; 0.05). These results suggest that in the presence of SAP, maize leaf and grain △<sup>13</sup>C could be good indicators for evaluating maize WUE during periods of low rainfall.

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