Differences In Water Uptake Research Articles

Comparative study of water uptake and photosynthetic gas exchange between scrub and fringe red mangroves, Rhizophora mangle L.

The red mangrove (Rhizophora mangle L.) occurs frequently in both scrub and fringe mangrove forests. Our previous study demonstrated that individuals of this mangrove species growing in scrub and fringe forests differ significantly in both morphological and physiological characteristics. To further characterize physiological differences between scrub and fringe mangroves, we compared their differences in water uptake and photosynthetic gas exchange during different seasons. In the wet season (June-October, 1990), scrub mangroves showed lower δD and δ18O values of stem water than fringe mangroves, indicating more usage of rain-derived freshwater. In the dry season (Jan-April, 1991), however, scrub mangroves utilized the same water source as fringe mangroves, reflected by their similar δD and δ18O values of stem water. Consistently, there were significant differences in predawn water potentials between scrub and fringe mangroves in the wet season (October 1990) with higher values for scrub mangroves, but no significant differences in the dry season (January 1991). Higher elevation in the scrub forest seems to be the major factor responsible for the shift of water sources in scrub mangroves. On Apr. 27 and Aug. 8, 1990, scrub mangroves showed lower CO2 assimilation rate, stomatal conductance, and intercellular CO2 concentration than fringe mangroves. There were no differences in these gas exchange characteristics on the other two measuring dates: Oct. 17, 1990 and Jan. 11, 1991. Instantaneous water use efficiency was significantly higher for scrub mangroves than for fringe mangroves on three of the four sampling dates. Similarly, leaf carbon isotope discrimination of scrub mangroves was always significantly lower than that of fringe mangroves, indicating higher long-term water use efficiency. Higher water use efficiency in scrub mangroves is a result of stomatal limitation on photosynthesis, which may entail considerable carbon cost to the plants.

Association of differences in seed vigour in long bean (Vigna sesquipedalis) with testa colour and imbibition damage

SUMMARYField emergence of 11 seed lots from six cultivars of long bean, all having laboratory germination of > 80%, ranged from 0 to 83%, indicating differences in seed vigour. Vigour differences occurred within and between cultivars, seed lots from cultivars with white or partly white testas having particularly poor emergence (0–21%) compared with those with brown or black testas (41–83% field emergence). The significant ranked correlations between field emergence and (i) solute leakage, measured by the electrical conductivity of seed soak water (r = –0·864), (ii) the percentage of cotyledons made up of completely living tissue, revealed by vital staining (r = 0·895), and (iii) the proportion of hard seeds (r = 0·916) indicated that lots with low vigour and potentially poor field emergence could be identified before sowing. Seed lots having low vigour imbibed water rapidly; the improved vital staining when seeds imbibed slowly indicated that damage occurred during imbibition and was a cause of low seed vigour. Rapid water uptake by low-vigour seed lots was partly explained by the incidence of seeds with cracked testas, but other factors could not be eliminated. The significance of differences in water uptake between cultivars differing in testa colour is discussed in relation to breeding for improved emergence.

Evapotranspiration of Cool-season Grasses Grown with Minimal Maintenance

Evapotranspiration (ET) of three perennial ryegrass (Lolium perenne L.) cultivars and one cultivar each of colonial bentgrass (Agrostis tenuis L.) and tall fescue (Festuca arundinacea L.) was measured in the field. Soil water depletion was measured with a neutron probe. Under minimal maintenance (i.e., no irrigation and infrequent mowing), ET was not significantly different for five perennial grasses. All grasses used more water than the bare-ground treatment. Soil water uptake was greatest in the upper soil layer (O to 25 cm) and decreased with depth. Few differences in water uptake were noted among grasses within each soil layer.

Effects of subsoil loosening and irrigation on soil physical properties, root distribution and water uptake of potatoes ( Solanum tuberosum)

The effects of irrigation and subsoil loosening to 0.45-m depth on potato (cv. ‘Record’) root growth and water uptake in a sandy loam soil are reported. Root length was measured by destructive core sampling, and the penetration of roots into the subsoil monitored using glass minirhizotrons. Subsoil loosening resulted in an increased root length below ploughd depth, but only in irrigated plots. Despite large reductions in soil penetration resistance, the maximum depth of rooting was little affected by the loosening operation. In the summer of 1984, soil drying occurred to 1.2-m depth, with the depth of water extraction consistently 0.3–0.4 m below the observed rooting depth. It was inferred that up to 13% of the total water uptake was supplied by capillary rise to the root zone. Root water uptake in unirrigated treatments was limited by soil water deficits in excess of 50 mm, resulting in significant reductions in tuber yield. However, no differences in water uptake and yield were observed between loosened and unloosened plots. Evidence from several sources suggested that soil shrinkage on drying allowed sufficient roots to penetrate the compact, unloosened subsoil. This may have been sufficient to maintain water uptake rates similar to those found in loosened treatments.

Summer Drought Response and Rooting Depth of Three Cool-season Turfgrasses

Abstract This study was conducted to determine root distribution, soil moisture depletion, and 32P uptake, as an indicator of water absorption, by Kentucky bluegrass (Poa pratensis L. ‘Fylking’), perennial ryegrass (Lolium perenne L. ‘Manhattan’), and tall fescue (Festuca arundinacea Schreb. ‘Kentucky 31’). 32P was injected at 6, 18, 30, 42, and 54 cm from the soil surface under each turfgrass plot on 18 July 1978. Leaf blade radioactivity revealed differences in uptake among species, but was inconsistent with rooting patterns. Root mass measurements below 36 cm in late August showed tall fescue > perennial ryegrass > Kentucky bluegrass. Root mass above 12 cm showed Kentucky bluegrass > tall fescue = perennial ryegrass. Soil water content (SWC) at three depths in August reflected root distribution for the three species. SWC was lowest under Kentucky bluegrass and highest under tall fescue at 6 cm. At 54 and 78 cm, SWC was highest under Kentucky bluegrass and lowest under tall fescue. SWC was better than 32P injection for detecting species differences in water uptake.

DIFFERENCES IN WATER UPTAKE RATES OF SOYBEAN ROOTS ASSOCIATED WITH TIME AND DEPTH

We developed a model of water uptake by soybean root systems. The model incorporated soil, root-soil contact, and radial and axial resistances to water flow. Parameters for the model were developed from field experiments conducted during the 1979 growing season on Ida silt loam, a loess soil, at Castana, Iowa. The specific water uptake rate decreased from 0.23 to 1 x 10-4 cm3 H2O cm-1 root day-1 as the soil water became depleted in a particular layer. The average conductivity of the soil-root system decreased linearly with age of plant. The water potential decrease along the vertical axis at the 20-cm depth was 0.0615 bar cm-1 when the transpiration rate was 1 cm day-1. A simulation of water uptake, based on a solution of the water flow equation with a sink term and performed with the aid of a differential equation solver DGEAR, tracks the seasonal withdrawal of water in a reasonably accurate manner.

INFLUENCE OF VESICULAR‐ARBUSCULAR MYCORRHIZAE ON WATER MOVEMENT THROUGH BOUTELOUA GRACILIS (H.B.K.) LAG EX STEUD*

SUMMARYRoot growth characteristics and water transport were compared between non‐mycorrhizal Bouteloua gracilis and vesicular–arbuscular mycorrhizal Bouteloua gracilis infected with Glomus fasciculatus. Mycorrhizal plants did not have significantly different leaf area or root length from non‐mycorrhizal plants, but did have significantly fewer and shorter root hairs. Mycorrhizal plants had 50% lower leaf resistance with no change in leaf or root water potentials; thus transpiration was increased 100% with a 50% reduction in whole‐plant, soil‐to‐root and root‐to‐leaf resistance. Assuming that the difference in water uptake was due to transport via the mycorrhizal hyphae, estimated fungus‐to‐root transport was 2.8 × 10−5 mg s−1 per hyphal entry point which compares favourably with evapotranspiration rates measured in other coenocytic fungi. Thus, one of the major factors causing increased water transport and reduced resistance to water through‐flow with mycorrhizal infection may be the increased surface area provided by the hyphae.

Wheat Seed Germination under Low Temperature and Moisture Stress1

AbstractCultivate differ inherently in their response towards drought. Only those adapted to arid and semiarid conditions become established into uniform and vigorous stands during germination under moisture stress and suboptimal temperature. Seed germination of four wheat cultivars, ‘Najah’ and ‘Mexi‐pak’ (Triticum aestivum L.), and ‘Hurani’ and ‘Jori’ (Triticum durum L.), were compared under suboptimal temperatures and various levels of simulated moisture stress. Components of water uptake, germination percentage, speed of germination, root growth, respiration rate, and germination recovery from stress were measured. The rate of water uptake decreased and the time required for germination increased when the seeds were incubated at 6 atm and higher. Seeds of the four cultivars germinated when their moisture content was approximately 50% on a fresh weight basis. Total germination was not affected by moisture stress levels up to 12 atm but was significantly reduced at 15 and 18 atm osmotic tensions. Rate of root growth, speed of germination, and respiration rates were inversely related to moisture stress. Low moisture stress (3 atm) did not inhibit root growth. Significant differences were found among cultivars in the parameters studied. Perforating the pericarps did not eliminate the differences in water uptake and respiration rates between cultivars. Prolonged exposure of ungerminated seed to high osmotic tensions at low temperatures showed high seed germination recovery. These data suggest that any of the germination criteria used can be effective in selecting droughtresistant cultivars.

Changes in seed tubers after planting

The changes after planting in weight and dry matter content of seed tubers were studied. The weight was found to increase after planting owing to uptake of water from the soil. The dry matter content decreased rather rapidly. The changes in weight varied within wide limits for individual tubers, showing great differences in water uptake between the tubers. These differences were also demonstrated in a soaking experiment. The variation in water uptake between tubers could partly be explained by variations in the soil but the variation between the seed tubers seemed to be more important.

Effect of Sterculia foetida oil on uptake of water by the avian egg yolk.

SummaryThe yolks of eggs from hens having a one-egg clutch average took up significantly more water than those from hens having 2-4 egg clutch sizes. Yolks from hens having 2, 3, and 4 egg clutch, sizes showed no significant differences in water uptake. Yolks from eggs stored overnight and from hens given Sterculia foetida oil were not significantly heavier and did not take up more water than eggs from hens given corn oil. However, when the eggs were stored one month the yolks from the hens fed Sterculia foetida oil increased 20% in weight and showed an 80% greater water uptake than those from the corn oil fed hens.