Showing papers on "Transpiration published in 1983"

Compromises between water-use efficiency and nitrogen-use efficiency in five species of California evergreens

Abstract: In five California evergreen trees and shrubs cooccurring in this study but most common in habitats of different moisture availability, leaf nitrogen was a major determinant of photosynthetic capacity. Within each species, stomatal conductance was highly correlated with photosynthetic capacity, resulting in little variation in the concentration of CO2 in the intercellular spaces. Among species, intercellular CO2 concentrations varied significantly. Under controlled conditions, the leaves that realized the highest photosynthesis per unit of leaf nitrogen tended to realize the lowest photosynthesis per unit of water transpired. The ratio of photosynthesis to transpiration, an instantaneous measure of intrinsic water-use efficiency, was highest in the species commonly found in the direst habitats and lowest in the species most common in the wettes habitats.

Leaf age and seasonal effects on light, water, and nitrogen use efficiency in a California shrub.

Abstract: Photosynthetic capacity, leaf nitrogen content, and stomatal conductance decreased with increasing leaf age in the chaparral shrub, Lepechinia calycina, growing in its natural habitat Efficiency of resource use for three resources that potentially limit photosynthesis did not, however, decrease with increasing leaf age Light-use efficiency, given by the quantum yield of photosynthesis at low light intensities, was unaffected by leaf aging but decreased slightly through the winter and spring growing season Water-use efficiency, the ratio of photosynthesis to transpiration at light saturation and with a constant water vapor concentration gradient, was not affected by leaf aging or seasonal change Nitrogen-use efficiency, the ratio of photosynthesis at light saturation to leaf nitrogen content did not change with leaf age but was lower in the leaves with the highest specific weights This ensemble of leaf-age effects is consistent with the hypothesis that aging represents resource redistribution and not uncontrolled deterioration

Stomatal Sensitivity to Carbon Dioxide and Humidity A Comparison of Two C3 and Two C4 Grass Species

Abstract: The sensitivity of stomatal conductance to changes of CO2 concentration and leaf-air vapor pressure difference (VPD) was compared between two C3 and two C4 grass species. There was no evidence that stomata of the C4 species were more sensitive to CO2 than stomata of the C3 species. The sensitivity of stomatal conductance to CO2 change was linearly proportional to the magnitude of stomatal conductance, as determined by the VPD, the same slope fitting the data for all four species. Similarly, the sensitivity of stomatal conductance to VPD was linearly proportional to the magnitude of stomatal conductance. At small VPD, the ratio of intercellular to ambient CO2 concentration, Ci/Ca, was similar in all species (0.8-0.9) but declined with increasing VPD, so that, at large VPD, Ci/Ca was 0.7 and 0.5 (approximately) in C3 and C4 species, respectively. Transpiration efficiency (net CO2 assimilation rate/transpiration rate) was larger in the C4 species than in the C3 species at current atmospheric CO2 concentrations, but the relative increase due to high CO2 was larger in the C3 than in the C4 species.

Diurnal and seasonal water relations of the desert phreatophyte Prosopis glandulosa (honey mesquite) in the Sonoran Desert of California

Abstract: Diurnal and seasonal water relations were monitored in a population of Prosopis glan- dulosa var. torreyana in the Sonoran Desert of southern California. Prosopis glandulosa at this research site acquired its water from a ground water source 4-6 m deep. Measurements of diurnal and seasonal cycles of aboveground environmental conditions, soil moisture, and soil water potential (to 6 m depth) were taken to ascertain environmental water availability and water stress. Leaf water potential, leaf conductance, leaf transpiration, relative saturation deficit of leaves, osmotic potential, and turgor potential were measured to evaluate plant adaptations to environmental water stress. Soil water potential was low (-4.0 to -5.0 MPa) in surface soil in relation to deep soil (-0.2 MPa). This difference was due to high surface soil salinity and low surface water content. The climatic conditions at the research site produced extreme water stress conditions in summer months when temperatures reached 50'C, vapor pressure deficit (VPD) reached 8 kPa, and surface soil water potential was below -4.5 MPa. Although considerable plant water stress developed in these trees (midday leaf water potential -4.8 MPa), osmotic adjustment occurred and turgor was maintained on a diurnal and seasonal cycle. Prosopis glandulosa has adapted to avoid water stress by utilizing deep ground water, but this phreatophyte has also evolved physiological adaptations, such as osmotic adjustment and seasonally changing stomatal sensitivity to VPD, which result in greater tolerance of water stress.

Defoliation responses of western wheatgrass populations with diverse histories of prairie dog grazing.

Abstract: Photosynthesis and regrowth were compared over a 10-day period following defoliation of about 75% of the tillers of western wheatgrass (Agropyron smithii) plants collected from a black-tailed prairie dog (Cynomys ludovicianus) town and a grazing exclosure at Wind Cave National Park, South Dakota. Prior to defoliation, dog town plants had more tillers, but fewer leaves per tiller, shorter and narrower leaf blades, more horizontal leaves, and higher leaf blade/leaf sheath ratios than plants from the grazing exclosure. Rates of net photosynthesis (PN) did not differ significantly among plants of the two populations, either prior to or following defoliation. From Days 2–10 following defoliation, PN of remaining undamaged leaves averaged 104% of predefoliation rates while PN of similar leaves on non-defoliated plants declined steadily with time. averaging only 79% predefoliation rates during this period. Following defoliation, transpiration rates followed similar trends to CO2 exchange, and rates did not differ between plants of the two populations. Absolute rates of leaf elongation and shoot production were greater in plants from the exclosure. However, defoliation of plants from the exclosure population resulted in a 20% reduction in their cumulative shoot dry weight, while cumulative shoot dry weight of plants from the prairie dog town was not significantly affected by defoliation. This apparent ability of plants from the prairie dog town population to withstand defoliation better than plants from the exclosure was atributed to factors such as the higher leaf blade/leaf sheath ratio and more horizontal leaf angles of plants from the former population.

The role of peristomatal transpiration in the mechanism of stomatal movement

Abstract: Abstract. Peristomatal transpiration is defined as the relative high local rate of cuticular water loss from external and internal surfaces around the stomatal pore and its decisive role in the control of stomatal movement is re-emphasized. As the resistance towards changes in air humidity is low in the pore surroundings, the state of turgor is particularly unsteady there. Due to the inherent instability the guard cell ‘senses’ fluctuations in the supply-demand relationship of water and is thus the control unit proper. The environmental variables (supply and demand) are cross-correlated within the subsidiary cell and the information is transmitted to the guard cell through the water potential gradient between the two cells. A conceptual segregation of a ‘humidity response’ by ‘passive’ stomatal movements is rejected. As ions always accumulate at the most distant point of the liquid path and as this point varies with pore width according to the prevailing water potential gradients, it is felt that the water stream is causing the characteristic pattern of ion distribution within the epidermis. Passive import of ions is attributed to local concentration gradients which are steepened by continuous supply and by water uptake into the guard cell in response to starch hydrolysis. A mechanistic model supplements the discussion.

Calculation of Leaf Photosynthetic Parameters Considering the Statistical Distribution of Stomatal Apertures

Abstract: It was shown earlier (Laisk, Oja, and Kull, 1980) that different stomata on a barley leaf are open to different degrees. Therefore, stomatal conductance is a quantity which is statistically distributed over a large range in the geometry of one leaf. Gas exchange measurements based on transpiration rates represent the average value of stomatal conductance in the leaf chamber. The conventional method of calculating mesophyll resistance involves subtracting stomatal resistance from total leaf resistance. It is incorrect, however, to average the stomatal resistance before this subtraction. Therefore, the conventional method for calculating the mesophyll resistance contains an error as it neglects the statistical distribution of stomatal apertures. The error is significant when the diffusion resistance between neighbouring substomatal cavities is large and when stomatal apertures vary over a wide range.

Effect of drought stress and vesicular–arbuscular mycorrhiza on citrus transpiration and hydraulic conductivity of roots

Abstract: Summary Infection of rough lemon seedlings (Citrusjambhiri Lush) by the vesicular–arbuscular mycorrhizal (VAM) fungus, Glomus intraradices (Schenck and Smith), increased root growth and transpiration rate and reduced leaf water potentials relative to non-infected control plants. Half of the VAM and control plants were subjected to three drying cycles each of 5 to 7 days. The hydraulic conductivity of previously drought stressed root systems was lower than that of the well-watered plants and VAM infection further reduced root conductivity. These data suggest that the higher root densities and higher transpiration rates of VAM infected plants may have depleted soil water more quickly than the non-infected seedlings and resulted in more severe water stress conditions during drought cycles.

Drought relations of shrub species: assessment of the mechanisms of drought resistance.

Abstract: Relatively static factors such as depth of rooting and cuticular conductance and relatively dynamic factors such as stomatol control and changes in the components of water potential were used to assess the drought resistance characteristics of six deciduous shrub species. Predawn water potential during a prolonged drought averaged-2.13 and-3.51 MPa in species known to have deep and shallow patterns of rooting, respectively. It is thus surprising that the osmotic potential at the turgor loss point averaged only-3.01 MPa in the shallow rooted group. The water potential at which irreversible cell damage occurred was the same in both groups (-4.9 MPa), and minimum values observed in the field never dropped below-4.0 MPa. There was, however, a pronounced difference between the two groups with regard to stomatal behavior. This allowed us to characterize the deep-rooted species as avoiders of stress which would cause prolonged stomatal closure whereas the shallow-rooted species had to tolerate prolonged periods of closed stomata.

Estimation of evaporation from non-vegetated surfaces using natural deuterium

Abstract: Loss of water by evaporation from bare surfaces is difficult to measure, because, like transpiration, it is subject to the vagaries of climate and water potential. Such loss can be a dominant parameter in the water balance of arid or semi-arid areas. Classical soil physical and meteorological methods can be used to estimate evaporative fluxes over short time periods, but are difficult to use over the longer times which are appropriate for most water balance studies. We describe here a new method for the estimation of evaporation from a bare surface based on enrichment of natural deuterium. The advantage of this technique is that it provides an integrated measure over relatively long periods of time. Using this method on data collected from the bed of Lake Frome, a normally dry salt lake in Central Australia, we find that the evaporation rate from the ‘dry’ lake surface is 63 mm yr−1.

Ecophysiology of two solar tracking desert winter annuals : IV. Effects of leaf orientation on calculated daily carbon gain and water use efficiency.

Abstract: This paper represents an empirical study on the effect of different leaf orientations on the daily carbon gain and transpirational water loss of desert winter annuals. Laboratory physiological data on Malvastrum rotundifolium (Gray) and Lupinus arizonicus (Wats) were combined with energy budget concepts and field measurements of water relations and leaf movements to predict carbon gain patterns for horizontally oriented, diaheliotropic and paraheliotropic leaf movement types. The results showed contrasting patterns of carbon gain and water loss. L. arizonicus, which is capable of both dia- and paraheliotropic leaf movements, had the lowest rates of daily carbon gain and water loss. But these low rates resulted in the highest water use efficiencies under early season conditions and high water availability. M. rotundifolium, a diaheliotropic species, was predicted as having the highest rates of carbon gain and water loss on a daily basis over a wide range of environmental conditions and water availability. Despite possessing the highest rates for transpiration, its water use efficiency was higher in relation to other leaf movement types, under a variety of conditions. This result was extremely sensitive to soil water availability. The results were discussed in relation to the ecological ramifications of leaf movements in arid land annuals.

The water balance of post-monsoonal dryland crops

Abstract: Six dryland crops (mungbean, cow pea, soya bean, groundnut, maize and sorghum) and two rice cultivars (C·171·136 and IR 36) were grown under rainfed and irrigated conditions on a dryland site with a clay loam soil at the International Rice Research Institute, Philippines. After the first 30 days of growth there was no effective rain, and the rainfed crops encountered different water deficits. Crop productivity, leaf area, plant water status, root distribution, and soil water use were measured.Neither rice cultivar yielded seed under rainfed conditions, but all other crops did. With mungbean and cow pea there was little difference between the yields under rainfed and irrigated conditions, but groundnut, soya bean, sorghum and maize gave higher yields under irrigation.The rainfed crops extracted different amounts of stored soil water, ranging from 100 mm for IR 36 to 250 mm for groundnut. The different amounts were associated with different growth durations, rooting depths and rates of soil water depletion from within the root zone. Biological productivity of the six rainfed crops with the C 3 photosynthetic pathway was linearly related to transpiration, which was estimated from soil water extraction and soil evaporation. Biological productivity per unit of transpiration for the two crops with the C 4 pathway was 2·2 times higher than for those with the C 3 pathway. The different seed yields of the rainfed crops were due to differences in harvest index and the chemical composition of seeds, as well as to biological productivity.The results are discussed in relation to the potential for growing dryland crops after rice in rice-based cropping systems.

Bunchgrass architecture, light interception, and water-use efficiency: assessment by fiber optic point quadrats and gas exchange.

Abstract: The bunchgrass growth form, which is very prominent in water-limited environments, can result in considerable self-shading of photosynthetically active foliage. The consequences of this growth form for light interception and water-use efficiency (photosynthesis/transpiration, P/T) were investigated for two Agropyron species which differ in tussock density and degree of self-shading. During the period of most active gas exchange, the tussocks were very compact and photosynthesis of shaded foliage was markedly light-limited. Stomatal control of older shaded foliage was poorly attuned for water-use efficiency. At low light, P/T decreased and intercellular CO2 concentrations increased. Despite differences in architecture and amount of shaded foliage, P/T of whole tussocks under ambient field conditions did not differ between these species. Partial defoliation decreased, rather than increased, P/T, primarily as a result of the poor photosynthetic light harvesting by the remaining foliage. Despite self-shading, the architecture of widely-spaced bunchgrasses provides for interception of as much direct beam solar radiation as is calculated for a rhizomatous grass occupying an area six-fold greater than the ground area underneath the canopy of these bunchgrasses.

Control of plant growth by nitrogen: differences between cereals and broadleaf species

Abstract: . In four dicotyledonous species low levels of N strongly inhibited leaf expansion during the day but had little or no effect at night. In contrast, daytime and night-time expansion were equally affected in four cereal species. The results support the general concept that in dicotyledons, N controls leaf expansion through its effects on hydraulic conductivity. In such N-limited plants, water deficits generated by transpiration may inhibit daytime cell expansion. In cereals, cell expansion and transpiration occur in separate zones of the leaf and are apparently unrelated. Growth analysis showed that low levels of N inhibited leaf area growth more strongly in dicotyledons than in cereals, but had similar effects on net assimilation rates of plants in the two groups. As a result, dry matter production was more efficient in cereals than in dicotyledons when N was limiting.

Associations between plant production and some physiological components of drought resistance in wheat

Abstract: . Drought resistance in terms of plant production under conditions of drought stress was previously defined for several spring wheat (Triticum aestivum L.) varieties. Four varieties, differing in their drought resistance by this definition, were compared in their physiological responses to water stress, as induced by polyethylene glycol 6000 in the growth medium. Drought resistance was associated with osmotic adjustment, total root mass production under stress, maintenance of some stomatal permeability under stress, and maintenance of turgor at a given level of drought stress, by either osmotic adjustment or elevated plant water potential. Drought resistance was not associated, in this experiment, with plant top growth under stress or non-stress conditions, maximum leaf area per plant, plant transpiration, and total root mass production under non-stress conditions.

Effects of mannose on photosynthetic gas exchange in spinach leaf discs.

Abstract: When mannose is provided in the transpiration stream to spinach (Spinacia oleracea) leaf discs, a series of specific and nonspecific changes occur in CO2 and H2O vapor exchange as a function of feeding time. The initial increases in apparent photosynthesis and transpiration are nonspecific effects due to osmotic changes leading to passive stomatal opening. The mannose-specific effects are: (a) time-dependent changes in the CO2 concentration required for saturation; (b) complex kinetics of the inhibition of CO2 assimilation dependent on CO2 and O2 concentrations and the duration of feeding (high CO2 and low O2 lead to rapid inhibitions of photosynthesis); (c) elimination of the capacity of 2% O2 to stimulate photosynthesis; and (d) oscillations in the CO2 exchange rate following transitions from 20% to 2% O2. The mannose-specific effects are reversible by orthophosphate. The mannose-dependent changes in gas exchange are attributed to altered [ATP]/[ADP] ratios.

Effect of Interruption of Flow Path on Stomatal Conductance of Abies amabilis

Abstract: Wounding of root or stem water conduction systems or cooling of roots in Abies amabilis produced rapid stomatal closure independent of evaporative demand or leaf water potential. The response also occurred in a branch if its xylem was only partially cut, but did not occur if the branch was completely severed. Removing part of the root system or cooling the roots produced the same effect as partial severing of the stem. The speed and uniformity of stomatal closure indicated that the stimulus was physical, linked to water flux in the xylem, and not caused by release of a chemical stimulus at the point of xylem flow disruption. The results suggested that stomatal closure could be rapidly induced with a change in the flux of water through the soil-plant-atmosphere continuum.

Water Relations and Growth of the flacca Tomato Mutant in Relation to Abscisic Acid

Abstract: The flacca mutant in tomato (Lycopersicon esculentum Mill. cv Rheinlands Ruhm) was employed to examine the effects of a relatively constant diurnal water stress on leaf growth and water relations. As the mutant is deficient in abscisic acid (ABA) and can be phenotypically reverted to the wild type by applications of the growth substance, inferences can be made concerning the involvement of ABA in responses to water stress. Water potential and turgor were lower in leaves of flacca than of Rheinlands Ruhm, and were increased by ABA treatment. ABA decreased transpiration rates by causing stomatal closure and also increased the hydraulic conductance of the sprayed plants. Osmotic adjustment did not occur in flacca plants despite the daily leaf water deficits. Stem elongation was inhibited by ABA, but leaf growth was promoted. It is concluded that, in some cases, ABA may promote leaf growth via its effect on leaf water balance.

Effects of flooding on leaf water potential and stomatal resistance in bruguiera gymnorrhiza (l.) lam

Abstract: SUMMARYThe effects of 10, 20, 40 and 80 days of flooding on stomatal responses in the halophyte,Bruguiera gymnorrhiza (L.) Lam were investigated. Measurements were made of leaf waterpotential and stomata! resistance (r^) during the period of flooding, and continuing for 12 to14 days after its termination.Generally, plants flooded for prolonged periods had lower leaf water potentials than thecontrols both during and after flooding. Prolonged flooding also resulted in higher r^ duringflooding and continuing for 8 to 10 days afterwards. Leaf water potentials decreased withincrease in the duration of flooding. Decrease in leaf water potential was also associated withan increase in r,.Prolonged flooding also resulted in ultrastructural modifications. The chloroplasts had smallergrana and the lamellae were considerably swollen. There also appeared to be some degradationof thylakoid membrane structure.INTRODUCTION Salinization of agricultural land and the resultant loss of productivity have, inrecent years, led to renewed interest in salt tolerance in halophytes (Jefferies, 1981).Although most plants are capable of adjusting osmotically to tolerate low levelsof salinity, growth under saline conditions, especially of glycophytes, is less thannormal (Hoffman, Shalhevet and Meiri, 1980). The most significant problems forplants existing in saline areas are high salt content and low soil water potential(Cavalieri and Huang, 1979).In addition to being salt tolerant, many halophytes in the intertidal zone canwithstand waterlogging or prolonged periods of tidal inundation. The efTects offlooding on glycophytes have been investigated by a number of workers, and theirgrowth has been found to be inhibited by flooding (Kramer and Kozlowski, 1960;Gill, 1970). Reduction in growth was correlated with decreases in water absorption,transpiration and photosynthesis (Parker, 1950; Kramer and Kozlowski, 1960).Flooding was also found to induce stomatal closure (Pereira and Kozlowski, 1977).Studies on the effects of flooding in halophytes are few (Naidoo and Naidoo, 1981;Cooper, 1982). It is important to understand the water relationships of halophytesand to determine if their responses differ physiologically from those ofglycophytes.In this study, greenhouse experinnents were conducted to determine the effectsof various periods of flooding on stomatal responses in the halophyte, Bruguieragymnorrhiza (L.) Lam, a local mangrove species. Leaf water potential was usedas a measure of plant water status and diffusion resistance as an indication ofstomatal aperture.

Stomatal response to vapour pressure deficit and the effect of plant water stress

Abstract: The dynamic response of stomata to changes in atmospheric humidity was investigated in Fragaria × ananassa Duch., Picea engelmannii Parry, and Pseudotsuga menziesii (Mirb.) Franco; and the effect of water stress on this response was determined in Pseudotsuga menziesii. The plants were rotated through three regimes of ambient temperature and vapour pressure deficit: 35°C–3. 5kPa, 35°C–0. 5 kPa, and 20°C–1. 5kPa. Branch and leaflet conductance were measured with a steady-state porometer, first at ambient vapour pressure deficit and then at one of four treatment conditions achieved by increasing or decreasing vapour pressure within the porometer cuvette. All three species showed similar stomatal response: enhanced conductance at low vapour pressure deficit and depressed conductance at high vapour pressure deficit. Engelmann spruce was more sensitive than Douglas fir and strawberry. Plant water status significantly altered stomatal response to vapour pressure deficit. The relationship of conductance of xylem water potential was linear under ambient conditions but became curvilinear when conductance was measured above and below ambient vapour pressure deficit. Between −0. 5 MPa and −2. 0 MPa xylem water potential, the stomata were sensitive to vapour pressure deficit, but below − 2. 0 MPa, the sensitivity decreased.