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Bingru Huang, Jack Fry, and Bin Wang

Understanding factors associated with drought resistance and recovery from drought stress in tall fescue (Festuca arundinaces Schreb.) is important for developing resistant cultivars and effective management strategies. Our objective was to investigate water relations, photosynthetic efficiency, and canopy characteristics of tall fescue cultivars (forage-type `Kentucky-31', turf-type `Mustang', and dwarf-type `MIC18') in responses to drought stress and subsequent recovery in the field and greenhouse. During drought stress under field conditions, `MIC18' had lower turf quality, more severe leaf wilting, and higher canopy temperature than `Mustang' and `Kentucky-31', indicating that `MIC18' was more drought-sensitive. The greenhouse study comparing `K-31' and `MIC18' showed that leaf water status, chlorophyll fluorescence, canopy green leaf biomass, and lead area index of both cultivars declined as soil dried. Reductions in relative water content, leaf water potential, chlorophyll fluorescence, canopy green leaf biomass, and leaf area index were more severe and occurred sooner during dry down for `MIC18' than for `Kentucky-31'. After rewatering following 14 days of stress, leaf water deficit and turf growth recovered, to a greater degree for `Kentucky-31' than for `MIC18'. However, soil drying for 21 days caused long-term negative effects on leaf photosynthetic efficiency and canopy characteristics for both cultivars.

Open access

Charles A. Brun, J. Thomas Raese, and Edward A. Stahly

Abstract

Mature bearing pear [Pyrus communis L. ‘Beurre d’Anjou’ (‘Anjou’)] trees in an arid climate were irrigated weekly at 125% of pan evaporation (wet), biweekly at 100% of pan evaporation (normal), or irrigated only twice (dry) during the summer (1980, 1981), and were fertilized with and without 0.9 kg of supplemental N. Prior to final fruit harvest in 1981, depletion of available soil moisture (ASM) averaged 10%, 16.7%, and 89% for the wet, normal, and dry treatments, respectively. Mid-day leaf water potential (ψL) was correlated with the level of ASM only on bright days of high vapor pressure deficit. Stomatal conductance (κs) and transpirational flux density (F) of dry treatment leaves was lower than that of either wet or normal treatment leaves ψL exceeded −1.4 to −1.7 MPa. Resistance to vapor (water) transport (Rν) of fruit was independent of irrigation regime. Terminal buds had set on shoots from all 3 irrigation regimes at 58 days after full bloom (AFB) in 1981, but resumed growth on normal and wet treatment shoots at 87 days AFB. On 7 of 10 sampling dates during 1981, dry treatment fruit weighed less than normal or wet treatment fruit.

Open access

Merle L. Weaver and H. Timm

Abstract

The effect of temperature, soil moisture, and diurnal variations in plant water content on pollen viability (PV) in bean (Phaseolus vulgaris L.) genotypes was investigated under field conditions in 1981 and 1982. Each year PV, relative water content (RWC), and leaf water potential (LWP) of each cultivar at mean soil moisture tensions (MSMT) of −0.05 and −0.10 MPa were reduced significantly between 0700 hr and 1400 hr. At a MSMT of −0.05 MPa, PV and RWC of both cultivars significantly increased between 1400 hr and 1900 hr. During the same period, the LWP of ‘California Light Red Kidney’ increased to the 0700-hr level, but remained at the 1400-hr level in ‘Gloria’. At a MSMT of −0.10 MPa, PV significantly increased in ‘Gloria’ but failed to increase in ‘California Light Red Kidney’ between 1400 hr and 1900 hr. RWC remained at the 1400-hr level in both cultivars. LWP of ‘California Light Red Kidney’ remained at the 1400-hr level, but continued to decline below the 1400-hr level in ‘Gloria’ during the same period. PV declined as both RWC and LWP decreased. A relative value for the simultaneous contribution of both high ambient temperature and the water status of bean plants to loss of PV was calculated.

Open access

E. L. Proebsting, S. R. Drake, and R. G. Evans

Abstract

‘Delicious’ and ‘Golden Delicious’ apples (Malus domestica Borkh.) on seedling rootstock were grown with trickle and sprinkler irrigation, both operated at high frequency of irrigation (daily). Trees with trickle irrigation developed lower leaf water potentials and produced less vegetative growth than trees with sprinkler irrigation, but fruit and productivity were similar. Apples from the trickle-irrigated trees had less water content and higher soluble solids than those from sprinkler-irrigated trees. Titratable acidity tended to be lower and both red color in ‘Delicious’ and yellow color in ‘Golden Delicious’ tended to be higher in fruit from trickle-irrigated trees than from sprinkled trees; firmness at harvest was similar regardless of irrigation procedure. Storage life was not influenced consistently by irrigation. Where differences did occur, the fruit from trickle-irrigated trees was softer after storage. Changes in fruit quality similar to those observed in trickle-irrigated trees were produced by imposing, through high frequency deficit irrigation with sprinklers, similar moisture deficits on apple trees, as measured by leaf water potential.

Free access

R. Savé, J. Peñuelas, I. Filella, and C. Olivella

One-year-old gerbera plants subjected to 1 night at 5C had reduced leaf water losses and chlorophyll content and increased root hydraulic resistance, but stomatal conductance and leaf water potential did not change. After 3 nights, leaf water potential had decreased and leaf reflectance in the visible and the near-infrared had increased. Similarly, abscisic acid (ABA) in leaves had increased and cytokinins (CK) in leaves and roots had decreased, but ABA levels in roots did not change. After 4 days at 20C, root hydraulic resistance, reflectance and leaf water loss returned to their initial values, but leaf water potential and chlorophyll content remained lower. Leaf ABA levels reached values lower than the initial, while root ABA and leaf CK levels retained the initial values. These data suggest that in the gerbera plants studied, 3 nights at 5C produced a reversible strain but otherwise plants remained uninjured, so this gerbera variety could be cultured with low energetic inputs under Mediterranean conditions. The results may indicate that ABA and CK were acting as synergistic signals of the chilling stress. Spectral reflectance signals seemed to be useful as plant chilling injury indicators at ground level.

Free access

C.P. Sharma and Sandhya Singh

When grown in refined sand with one-twentieth normal K supply, cauliflower (Brassica oleracea L. var. botrytis L. cv. Pusi) had lower dry matter and tissue concentration of K than the controls and developed visible symptoms characteristic of K deficiency. In K-deficient plants, the specific leaf weight, diffusive resistance, and proline concentration in leaves were significantly higher and relative water content (RWC), leaf water otential (ψ), stomatal aperture, stomatal density, and transpiration rate were significantly lower than in control plants. When K-deficient plants were supplied additional Na to the extent K was deficient, Na concentration in the plants increased and the plants recovered from the K deficiency effect on free proline concentration, RWC, leaf water potential, stomatal aperture, stomatal density, specific leaf weight, diffusive resistance, and transpiration.

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Mathieu Ngouajio, Guangyao Wang, and Ronald G. Goldy

water potential was measured using the third fully expanded leaf. Five leaves were collected in each plot before sunrise ( Rudich et al., 1981 ), enclosed in zip-lock bags, and put in an insulated box. Leaf water potential was measured after leaf

Free access

Pedro Perdomo, James A. Murphy, and Gerald A. Berkowitz

Understanding the factors influencing the performance of Kentucky bluegrass (Poa pratensis L.) cultivars under summer stress is necessary for developing criteria for identifying resistant germplasm. The objectives of this study were to evaluate two Kentucky bluegrass cultivars for leaf water (ψl) and osmotic potential (ψπ), stomatal resistance (Rs), leaf: air temperature differential (ΔT) and determine the relationship of these parameters to drought and heat tolerance. Stress-resistant (`Midnight') and susceptible (`Nugget') cultivars were evaluated in a field study during 1993 and 1994 under moisture-limiting conditions. Leaf water potential for `Nugget' was higher than for `Midnight' in 1993 and similar in 1994. `Midnight' had lower ψπ than `Nugget' during the evaluation period in 1994. `Midnight' maintained more open stomata (lower Rs) and lower ΔT than `Nugget' at the end of the dry down period when `Nugget' was showing visual signs of stress. `Midnight' and `Nugget' had similar root weight at the 0- to 45-cm depth zone in 1994. Lower basal osmotic potential (i.e., higher solute concentration) may be the physiological mechanism allowing larger stomatal aperture in `Midnight'. Greater transpirational cooling in `Midnight' relative to `Nugget' was correlated with higher turf quality for `Midnight'.

Free access

J. Girona, M. Mata, D.A. Goldhamer, R.S. Johnson, and T.M. DeJong

Seasonal patterns of soil water content and diurnal leaf water potential (LWP), stomatal conductance(gs), and net CO2 assimilation (A) were determined in a high-density peach [Prunus persica(L) Batsch cv. Cal Red] subjected to regulated deficit irrigation scheduling. The regulated deficit irrigation treatment caused clear differences in soil water content and predawn LWP relative to control irrigation treatments. Treatment differences in midday LWP, gs, and A were also significant, but not as distinct as differences in predawn LWP. Leaves on trees subject of the deficit irrigation treatment were photosynthetically more water-use-efficient during the latter part of the stress period than were the nonstressed trees. Midday LWP and gs, on trees that received the regulated deficit irrigation treatment did not recover to control treatment values until more than 3 weeks after full irrigation was resumed at the beginning of state III of fruit growth, because of water infiltration problems in the dry soil caused by the deficit irrigation. The regulated deficit irrigation treatment caused only a 8% reduction in trunk growth relative to the control, but resulted in a 40% savings in irrigation requirements.

Open access

E. L. Proebsting Jr., J. E. Middleton, and M. O. Mahan

Abstract

Cherry (Prunus avium L.) and prune (P. domestica L.) trees were trickle irrigated daily or weekly at 100%, 50%, and 15% of evaporation from a standard Class “A” pan, adjusted to the area of the tree canopy (Ec), for one full growing season. Soil moisture remained above the wilting point throughout the soil profile with 100% Ec but reached the wilting point except for a wetted zone near the emitters for 50% Ec and 15% Ec. Leaf water potential of shaded cherry leaves at midday averaged near -14 bars for 100% Ec, near -20 bars for 15% Ec, reaching as low as -28 bars for prunes in late July and August. Growth of fruit and vegetative parts was reduced by severe stress but the trees survived on 15% Ec. Prunes recovered to normal yield and growth by the second year after treatment. Peripheral branches of cherries died back during the year of treatment and in the following year. Cherries grew and fruited normally by the third year after treatment except for reduced bearing surface.