Leaf Diffusive Resistance Research Articles

A comparison of pressure chamber, leaf-press, and canopy temperature for four species under humid conditions

Numerous techniques are currently available for measurement of plant water status in field environments, including pressure chambers and indices based upon infrared-determined canopy temperatures. The Campbell-Brewster (J-14) leaf press has been promoted as a compact alternative to the pressure chamber for plant water potential determination. In-depth comparisons of the J-14 ( Ψ J) with the pressure chamber ( Ψ x) or with canopy temperatures ( T c) and crop water stress index ( CWSI) have been limited, and an evaluation of the technique in a humid environment was needed. All three J-14 end points [exudation from cut ( Ψ Jc) or uncut leaf edges ( Ψ Ju) or darkening of interveinal areas ( Ψ Jd)] were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. None of the water status indicators correlated well with leaf diffusive resistance. Our data showed a species-related reliability of the J-14. The J-14 produced r 2 values above 0.7 for soybean [ Glycine max. (L.) Merr.] for all but comparisons with CWSI or T c minus air temperature (Δ T), and for corn ( Zea mays L.) for Ψ x only. The J-14 did not perform well for tomato ( Lypersicum esculentum Mill.) or rapeseed ( Brassica napus L.), and is probably best regarded only as a relative indication of plant water status in the absence of calibration with other techniques. Failure of Ψ x or J-14 to correlate well with CWSI underscores difficulty with CWSI measurement under humid conditions.

Influence of Root-zone Temperature on Growth of Ailanthus altissima (Mill.) Swingle

Abstract Growth of tree-of-heaven (Ailanthus altissima (Mill.) Swingle) seedlings was evaluated during a 28-day exposure to constant root-zone temperatures of 18°, 24°, 30°, and 36°C (64°,75°, 86°, and 97°F). Leaf area, stem length, root-to-shoot ratio, and shoot and root dry weights were greatest among plants with 24°C (75°F) root zones. Diminished growth among plants at high root-zone temperatures was associated with reduced leaf conductance. After 14 days of treatment, leaf diffusive resistance of plants in the 36°C (97°F) regime was eight times greater than that of plants with 24°C (75°F) root zones. Regulation of leaf gas exchange among plants with 36°C (97°F) root zones probably contributed to the maintenance of moderate leaf water potentials but limited the fixation of carbon necessary to sustain growth.

Growth and stomatal responses of sugar maple in irrigated and non-irrigated landfill cover soil

Irrigation increased sugar maple ( Acer saccharum Marsh.) growth and nitrogen content and reduced leaf diffusive resistance on a completed landfill site but not on an adjacent non-landfill control area. Even with irrigation, growth on the landfill was lower than in either the irrigated or non-irrigated control. Lower growth was associated with elevated soil CO 2 concentration and lower O 2 and soil moisture content. The soil gas atmosphere explained variation in leaf diffusive resistance on the landfill plot whereas air temperature, relative humidity and wind movement were correlated with resistance on the control.

Root-zone Temperature Affects Water Status and Growth of Red Maple

Abstract Red maple (Acer rubrum L.) plants were evaluated for their responses to 5 weeks of constant root-zone temperatures from 18 to 36C. Shoot lengths of plants grown with 18 to 30C root zones did not differ significantly from one another at any time during the study, and shoot dry weights of these plants were similar. However, after 21 days of exposure, shoot length of plants grown with roots at 36C was significantly less than that of plants with roots grown at 30C and below. Leaf area was greatest among plants with roots at 24C, and mean shoot and root dry weights of plants in the 36C treatment were 57% and 68% less, respectively, than those for plants with roots at 30C. Leaf diffusive resistance of plants grown at 36C was five times greater than for plants with root zones at 30C or below. Shoot water potential decreased with increasing temperature, but increased solute concentration in leaves of 36C-grown plants probably contributed to turgor maintenance.

The influence of transpiration on the equilibration of leaf water with atmospheric water vapour

Abstract. The authors examine the isotopic composition of leaf water, at natural abundance levels, as influenced by transpiration rate. The isotopic composition of water of wheat leaves (Triticum aestivum L. var. Aroona) was followed while their transpiration rate adjusted to ‘steady‐state’ environmental conditions. Leaf diffusive resistance was modified by short‐term salt treatment and by plant culture in either nutrient solution, free‐draining sand, or vermiculite. Resultant changes in 18O and 2H in leaf water are described and fitted to the model of Leaney et al. (1985). The treatments with lower transpiration rates were found to have a greater fraction of their leaf water equilibrated with water vapour in the atmosphere. Comparable results were obtained with both 18O and 2H, with some differences being interpreted in terms of turbulence in the vapour diffusion path. The fraction of the leaf water equilibrated with the atmosphere varied between leaves of different ages. However, this may have been due to their different positions in the canopy.

Leaf Water Potential, Relative Water Content, and Diffusive Resistance as Screening Techniques for Drought Resistance in Barley

AbstractRapid drought resistance screening techniques could accelerate selection of improved cultivars for semiarid areas. This study was conducted to determine if total leaf water potential, leaf relative water content, and leaf diffusive resistance could be used to differentiate between barley (Hordeum vulgare L.) cultivars differing in apparent drought resistance. Resistant and susceptible cultivars were selected by regressing individual cultivar yields against site mean yield for numerous yield trials. Individual plants were grown in cone‐tainers (plastic tubes 25 mm in diameter and 123 mm long). The lower 30 mm of the cone‐tainers were imbedded in sand so that roots emerging from the bottom of the cone‐tainers were in the capillary fringe above a water table in the sand. Fifty plants were grown at a time in a sand bed, five replications each of five resistant and five susceptible barley cultivars of either two‐ or six‐row head types. At the three‐leaf growth stage total leaf water potential (Ψt) was measured on the third leaf of each plant under low stress conditions (predawn). Water was then drained from the sand bed to stress the plants. Leaf diffusive resistance (LDR) was measured at 1000 and 1300 h each day as stress developed. When the PM diffusive resistance reached about 1000 s m−1, relative water content (RWC) of the second leaf was determined. All measurements were repeated in three different trials for each head type. Relative water content and Ψt differentiated between drought‐resistant and drought‐susceptible groups of two and six‐rowed barley at the 0.01 probability level in every trial. Leaf diffusive resistance differentiated between resistant and susceptible groups at the 0.01 or 0.05 level under low and high stress conditions. Neither RWC nor LDR allowed separation of cultivars within resistant or susceptible groups, but Ψ, did show differences between cultivars within groups. These techniques provide an easy method to screen for drought‐resistant barley.

Response of ‘Sonia’ roses to salinity at three levels of ambient CO2

SummaryThe effect of prolonged exposure of plants to a combination of both salinity and high CO2 concentration ([CO2]) is not easy to predict. The purpose of this work was to contribute to the clarification of this question for roses. ‘Sonia’ rose plants were placed in growth chambers for three consecutive flowering cycles, under conditions simulating winter in a controlled environment greenhouse in the desert. Plants were grown at three levels of [CO2] and four levels of salinity. Plants died or stopped growing when treated with 3 436 g m−3 salt. Subsequently, the highest concentration used was 2 577 g m−3 total soluble salt. Salinity tolerance increased at high [CO2]. Some combinations of CO2 and salt gave higher yields than those obtained with CO2 alone, due to a decrease in blindness. This suggests that salt, in the presence of high [CO2], changed the distribution of assimilates. Under high [CO2], salinity did not change plant water potential, but leaf diffusion resistance to water vapour (r1) increas...

THE EFFECT OF WATER DEFICIT ON N2(C2H2) FIXATION BY WHITE BEAN AND SOYBEAN

White bean (Phaseolus vulgaris L.) is generally reported to fix less N than soybean (Glycine max Merrill [L.]). Recent work has shown that in soybean the onset of physiological responses that conserve plant and soil water occurs at greater water deficits than in some other legumes. Little is known about water use regulation in white bean. Research was conducted to compare the responses of these two species to water deficit, particularly its effects on N2 fixation, in both controlled environment and field conditions. In the growth room, plant water potential, leaf diffusive resistance, acetylene reduction and nodule mass per plant were measured for both species during progressive drought, and compared to watered controls. In the field, the leaf diffusive resistance of irrigated and unirrigated plants of both species was measured, as was the soil water potential in plots where these crops were grown. Under conditions of increasing water deficit white bean reacts to conserve plant and soil water sooner than soybean: closing its stomates earlier under drought conditions and maintaining higher plant water potentials. White bean acetylene reduction declined more rapidly over time and over plant water potential levels, but not over changes in leaf diffusive resistance, than that of soybean, as the droughting progressed. In the field, under drought conditions, white bean root nodules senesced, while soybean nodules did not, and white bean was observed to exhibit more parahelionasty than soybean. The onset of physiological responses that conserve plant and soil water occurred at lesser water deficits in white bean than soybean, and this was reflected in more extreme effects on N2 fixation by white bean.Key words: White bean, soybean, water deficit, acetylene reduction, nitrogen fixation, nodulation

Plant-Water Relations of Young Highbush Blueberry Plants

Abstract Diurnal and seasonal measurements of leaf water potential (ψ1), leaf diffusive resistance (R1), and leaf stomatal conductance (gs) of highbush blueberry (Vaccinium corymbosum L. cv. Bluecrop) were made in 1984 and 1985. Marked diurnal variation in ψ1, R1, and gs was observed. The most negative values of ψ1 were usually reached by 1000 Central Standard Time and were maintained until late afternoon. Leaf stomatal conductance values were high in early morning, remained high throughout the day, and decreased in late evening. Stomata were absent on the adaxial leaf surface, while the abaxial surface averaged 553 stomata/mm2. Unexplained seasonal changes in ψ1 and R1 were noted in 1985. Leaf water potential and R1 were significantly correlated in one year. Leaf water potential and R1 were significantly correlated with air temperature and relative humidity, respectively, in both years.

Water relations of coconut palms as influenced by environmental variables

The influence of the agrometeorological parameters of radiation, temperature and vapour pressure deficit (VPD) on the development of stress in coconut palms ( Cocos nucifera L.) was studied. A steady state porometer was employed to measure both meteorological parameters and stomatal resistance under field conditions. Between 10.00 and 12.00 hours there were increases in radiation, temperature and vapour pressure deficit (VPD). During this period the stomatal resistance reached a maximum and the leaf water potential (Ψ) was reduced. During the wet season there was low radiation, temperature and VPD which resulted in the palms showing low stomatal resistance, whereas during the dry season the reverse situation occurred. West Coast Tall palms responded to dry weather through a high leaf diffusive resistance, while the hybrid dwarf X tall was susceptible to stress conditions.

Relationship of potassium deficiency and abscisic acid metabolism in Soyabean plants∗

Abstract The effects of abscisic acid (ABA) and K deficiency on leaf diffusive resistance were determined on soyabean (Glycine max L., cv. Amsoy 71) plants. Leaf diffusive resistance was measured on the lower surfaces of the primary leaves. Changes in leaf diffusive resistance, determined with the transient porometer, were found similar in both of the treatments compared with the control plants. 14C‐ABA (Abscisic acid) was given to roots of K‐deficient plants and specific radioactivities were found to increase in the primary leaves compared to K‐sufficient plants. Plants subjected to a K deficient stress induced through the roots were able to adapt to their environment by closing their stomata. This suggests that such adaptations are made possible by increasing the content of ABA in

Stomatal behaviour and leaf water potential of chilled and water‐stressed Solanum melongena, as influenced by growth history

Abstract Leaf diffusion resistance and leaf water potential of intact Solanum melongena plants were measured during a period of chilling at 6 °C. Two pretreatments, consisting of a period of water stress or a foliar spraying of abscisic acid (ABA), were imposed upon the plants prior to chilling. The control plants did not receive a pretreatment. In addition to intact plant studies, stomatal responses to water loss and exogenous abscisic acid were investigated using excised leaves, and the influence of the pretreatment observed. Chilled, control plants wilted slowly and maintained open stomata despite a decline in leaf water potential to –2.2 MPa after 2 d of chilling. In contrast plants that had been water stressed or had been sprayed with abscisic acid, prior to chilling, did not wilt and maintained a higher leaf water potential and a greater leaf diffusion resistance. In plants that had not received a pretreatment, abscisic acid caused stomatal closure at 35 °C, but at 6°C it did not influence stomatal aperture. The two pretreatments greatly increased stomatal sensitivity to both exogenous ABA and water stress, at both temperatures. Stomatal response to water loss from excised leaves was greatly reduced at 6°C. These results are discussed in relation to low temperature effects on stomata and the influence of preconditioning upon plant water relations.

SOME PHYSIOLOGICAL RESPONSES OF THEOBROMA CACAO VAR. CATONGO SEEDLINGS TO AIR HUMIDITY

SummaryThe stomata of three‐month‐old seedlings of Theobroma cacao L. var. Catongo were more open in high relative humidity (RH) (76 to 89%) than in low relative humidity (39 to 62 %). In both regimes, stomata closed gradually during the day, with the rate of closure accelerating in the late afternoon. Transpiration rate (TR) was correspondingly high early in the day and low late in the day. Average leaf diffusive resistance (r1) was 26% lower at the high RH. Nonetheless, TR was generally higher for plants in the low RH, because of the much greater vapour pressure gradient between the leaf and air. Abruptly lowering the RH at noon rapidly increased (r1) and increasing RH decreased r1, In another experiment conducted in constant high or low RH regimes, r1 was lower, the rate of net photosynthesis (Pn) was higher, leaf water potential (Φ) was lower (more negative), and TR was lower in the high RH regime. Water‐use efficiency (WUE) was higher in high than in low RH. The relationships between Pn and r1 were identical at high and low RH. Thus, differences in TR and WUE at high vs low RH were a direct result of variations in vapour pressure deficit (VPD) between the two humidity regimes. Stomatal opening and closing reflected direct effects of humidity on guard cells rather than responses to changes in bulk leaf Φ. In addition, root to leaf hydraulic conductivity apparently was greater at low than at high RH.

Differences in Drought Resistance between Two Corn Hybrids. I. Water Relations and Root Length Density1

AbstractCorn (Zea mays L.) hybrids are often selected for near optimal conditions of water availability, yet frequently are grown under less than ideal soil moisture. Different responses among corn hybrids to drought stress have been observed, but the physiological and morphological differences that confer drought resistance or susceptibility are not well understood. The objective of this study was to identify differences in leaf water relations, stomatal activity, and root length density distribution between two corn hybrids known to differ in their response to water stress. During the 1983 and 1984 growing seasons, two corn hybrids (Pioneer Brands 3192 and 3165) were subjected to three water management treatments: irrigated, rainfed, and stress during vegetative (1983) or reproductive (1984) growth. During periods of water stress, hybrid 3192 wilted 2 to 3 days sooner and maintained leaf water potentials (ΨL) and leaf turgor potentials (Ψp) that were 0.2 to 0.5 MPa and 0.1 to 0.3 MPa lower, respectively, than those of hybrid 3165. Water stressed plants of hybrid 3192 closed their stomata earlier during periods of water stress, but the relationship between leaf diffusive resistance and Ψp was similar for both hybrids, with stomata beginning to close as Ψp decreased below 0.4 MPa. Regardless of the stage of ontogeny, hybrid 3165 always maintained a lower Ψp at a given ΨL than hybrid 3192. However, the primary difference observed between the two hybrids was the ability of hybrid 3165 to simply avoid tissue desiccation by maintaining higher ΨL and Ψp. The deeper rooting profile of hybrid 3165 may have contributed to the maintenance of higher ΨL and Ψp during water stress.

THE EFFECTS OF LIGHT AND TEMPERATURE ON THE GROWTH OF AND BALANCES OF CARBON, NITROGEN AND POTASSIUM BETWEEN VICIA FABA L. AND APHIS FABAE SCOP.

SummaryThe effects of light, temperature and infestation by Aphis fabae Scop, on Vicia faba L. were examined in a factorial experiment. Light was 1116 or 40 μmiol m‐2 s‐1 PPFD and temperature 15/10 °C or 25/20 °C (16 h day/8 h night). Plants and aphids were harvested after 9 d at 25/ 20 °C and 13 d at 15/10 °C. High light and high temperature increased the relative growth rate (RGR) of aphid colonies, but without interaction. Under high light, alatae produced more nymphs which grew larger. High temperature did not affect nymph production, but mature apterae weighed less. More honeydew was produced at high light. High temperature increased honeydew at high light, but decreased it at low. Reduction in dry weight (d.w.) of infested plants was similar to the calculated dry matter (d.m.) ingested by the aphids except at high light/low temperature, where it was much less. Calculated NAR was increased by high light, but reduced by high temperature. In infested plants, ‘true’ NAR (calculated from plant d.w. + ingested d.m.) was compared with ‘apparent’ NAR (calculated from plant d.w. alone). Infestation decreased ‘apparent’ NAR, but the effect was small at high light/low temperature because ‘true’ NAR increased. Infested plants at low light/high temperature had negative ‘apparent’ NARs. High light and high temperature generally decreased leaf diffusive resistance, except that uninfested plants at high light/low temperature had large values. Stem, leaf and root d.w. were all increased by high light and decreased by infestation. Leaf carbohydrate showed similar responses. Chlorophylls were reduced at high light, particularly at low temperature in uninfested plants. These plants showed positive relationships between chlorophyll and (1) the starch: sucrose ratio and (2) leaf total nitrogen, but a negative relationship with leaf diffusive resistance. Leaf potassium (K) and amino nitrogen showed only small responses to light and temperature. Aphids retained > 80 % of N ingested and < 20 % of K. Ingested material contained more K than N, but the ratio of both to carbohydrate was much greater under low light, particularly at high temperature. Aphids under these conditions appeared starved of carbohydrate. Low light increased the proportions of proline, amides and ammonia in both leaf extracts and aphid honeydew.

Differences in Drought Resistance between Two Corn Hybrids. II. Component Analysis and Growth Rates1

AbstractRelatively little research has been conducted to evaluate differing responses to water stress among genotypes of the same species. The objective of this study was to identify differences in growth and development of plant parts resulting from water stress imposed on two corn (Zea mays L.) hybrids that had been observed to differ in their sensitivity to water stress. During 1983 and 1984, two corn hybrids (Pioneer Brands 3192 and 3165) were subjected to three water management treatments: optimal irrigation, rainfed, and stress during vegetative (1983) or early reproductive (1984) growth. Growth analysis revealed few differences between hybrids for leaf area index, and crop and seed growth rates when well‐watered or stressed during vegetative growth, except that hybrid 3192 showed more rapid early growth. When well‐watered, grain yield of hybrid 3192 was the same (1983) or higher (1984) than grain yield of hybrid 3165. However, the two hybrids differed in their ability to resist severe water stress. The greater grain yield of hybrid 3165 in the rainfed treatment was associated with relatively smaller reductions in crop growth rate, total biomass accumulation, seed number, effective filling period, and harvest index with stress when compared to hybrid 3192. The greater crop growth rate and final biomass and grain yield of hybrid 3165 during severe stress most likely resulted from the maintenance of higher leaf water and turgor potentials and lower leaf diffusive resistances that were apparently mediated by higher root length densities in deeper zones of the soil profile as described in a companion paper.

THE EFFECT OF WATERLOGGING ON INFECTION OF EUCALYPTUS MARGIN AT A SEEDLINGS BY PHYTOPHTHORA CINNAMOMI

SummaryThree‐ to four‐month‐old Eucalyptus marginata Donn ex Sm. (jarrah) were grown in the glasshouse in peat/sand at 20° C root temperature, infected with zoospores of Phytophthora cinnamomi Rands, added either 10 cm below the soil surface or flooded onto the soil, and various waterlogging regimes were imposed. When plants were infected but not waterlogged, the proportion of infected root length adjacent to the point where zoospores were added was low. More lesions were formed per metre root length on tap roots than on lateral roots, but lesions on lateral roots were longer than on tap roots. When plants were waterlogged for a 4 d period before the addition of zoospores, there was no increase in root infection. When plants were waterlogged at the same time or after the pots were inoculated, there was a significant increase in the proportion of root length infected. This was due to an increase in the number of lesions and not, in four of the five harvests, to an increase in lesion length.When inoculation and waterlogging were imposed at the same time, the increased number of infections was probably due both to the increased attraction of zoospores to anaerobically respiring roots and to increased zoospore motility in flooded soil. When waterlogging was imposed several days or weeks after the plants had been infected, the increased number of lesions was unlikely to have been due to residual zoospores in the soil, because their numbers declined exponentially. It was also unlikely to have been due to sporangia developing de novo on the roots after waterlogging had been imposed, because the O2 concentration of the soil solution was inadequate. It is probable, therefore, that the new infections originated from zoospores liberated from sporangia already formed on lesions before waterlogging was imposed.When plants were infected but not waterlogged, there was no effect on the leaf diffusive resistance, leaf relative water content and shoot xylem pressure potential between 1 and 28 d. When plants were flooded, the daily water loss decreased more rapidly and plants died more rapidly in the inoculated and waterlogged treatments than in the treatments which were only waterlogged. Infection by P. cinnamomi did not affect the proportion of xylem vessels occluded with tyloses in seven of the eight unflooded, and seven of the eight flooded, comparisons.

Recovery after Chilling: An Assessment of Chill-Tolerance inPhaseolusspp.

Guye, M. G, Vigh, L. and Wilson, J. M. 1987. Recovery after chilling: an assessment of chill-tolerance in Phaseolus spp.—J. exp. BoL, 38: 691–701. The chill-sensitivity of three Phaseolus spp. (eight cultivars) was assessed by measuring five different physiological parameters (leaf pigment loss, leaf diffusion resistance, relative growth rate recovery, change in leaf water content and the severity of leaf necrosis) on return to the warmth (23 °C/18 °C) following a brief but severe chilling treatment (24 h at 5 °C). In this way the genotypes could be ranked in order of increasing chill-sensitivity as follows: P. coccineus cvs Prizewinner and Streamline, P. vulgaris cv. 251 < P. vulgaris cvs 194, 222 and Seafarer < P. vulgaris cv. Tendergreen < P. aweus cv. Berken.

生態型の異なるメロンの耐乾性の差異

Physiological differences between melons with high and low drought resistance were studied.Melons with high drought resistance, which was estimated by leaf water saturation deficit (WSD) after water restriction, showed high osmosis resistance in isolated mesophyll cells.The leaf diffusive resistance of‘Howell’, an American cantalope with high drought resistance, was quickly modified when leaves were treated with abscisic acid (ABA), N6-benayladenine (BA) or gibberellic acid (GA3).‘Katsurashirouri’, a Japanese pickling melon with low drought resistance, did not respond to these growth regulators.Under non-stress conditions, the levels of ABA and gibberellic acid extracted from leaves of‘Howell’were slightly higher than those extracted from leaves of‘Katsurashirouri’. Under water stress, the level of ABA in leaves of‘Katsurashirouri’ increased more rapidly than in leaves of‘Howell’. The level of gibberellic acid in both cultivars decreased at the same rate under the same stress conditions. Under non-stress conditions, the cytokinin content was the same in both cultivars, but under water stress, cytokinin decreased more rapidly in‘Howell’than in ‘Katsurashirouri’.

Foliage temperature: Effects of environmental factors with implications for plant water stress assessment and the CO2/climate connection

Throughout the summer and fall of 1985, several day‐long sets of foliage temperature measurements were obtained for healthy and potentially transpiring water hyacinth, cotton, and alfalfa plants growing in a sealed and unventilated greenhouse at Phoenix, Arizona, along with concurrent measurements of air temperature, vapor pressure and net radiation, plus, in the case of the water hyacinths, leaf diffusion resistance measurements. Some data for these plants were additionally obtained out of doors under natural conditions, while dead, nontranspiring stands of alfalfa and water hyacinth were also monitored, both out of doors and within the greenhouse. Analyses of the data revealed that plant nonwater‐stressed baselines, i.e., plots of foliage‐air temperature differential versus air vapor pressure deficit for potentially transpiring vegetation, were (1) curvilinear, as opposed to the straight lines which have so often appeared to be the case with much smaller and restricted data sets, and (2) that these baselines are accurately described by basic theory, utilizing independently measured values of plant foliage and aerodynamic resistances to water vapor transport. These findings lead to some slight adjustments in the procedure for calculating the Idso‐Jackson plant water stress index and they suggest that plants can adequately respond to much greater atmospheric demands for evaporation than what has been believed possible in the past. In addition, they demonstrate that the likely net radiation enhancement due to a doubling of the atmospheric carbon dioxide concentration will have little direct effect on vegetation temperatures, but that the antitranspirant effect of atmospheric CO2 enrichment on foliage temperature may be substantial.