Relative Turgidity Research Articles

Effects of Environment on Growth and Survival of Douglas-fir Transplants

Variation in lifting date, planting date, planting site, seedling history, root treatment, and storage time were tested for their effects on Douglas-fir transplants. Survival, water status, types of damage, and both shoot and root growth were measured. Survival decreased with later spring planting date in the field, but this was partly offset by trends in browsing. Survival was greater at the lower elevation. Differences in seed lot, or conditions in the nursery, resulted in differences in tree size, which had some effects because the larger trees were browsed more. Survival and growth were not markedly different between root treatments. Cold storage increased survival of trees lifted late in the spring. The relative turgidity of leaves from bareroot trees in storage was related to lifting date and subsequent survival. Survival decreased severely as lifting date progressed through March.

Effect of Water Stress on Ethylene Production by Detached Leaves of Valencia Orange (Citrus sinensis Osbeck)

Detached leaves of Valencia oranges, Citrus sinensis Osbeck, emanated ethylene at markedly higher rates and contained more endogenous ethylene when placed under water stress at 55% relative humidity than when placed in water-saturated air. Water stress induced defoliation from detached branches. Relieving the water stress of such leaves by transfer to a mist chamber resulted in lowering of the rates of ethylene emanation to the level occurring in leaves maintained continuously in a mist chamber. This ability to recover from the water stress was evident for only up to 10 to 20 hours of stress, when the relative turgidity of the leaves was 50 to 60%. Beyond that time the level of ethylene emanation of stressed leaves was not lowered by rehydration in a mist chamber; these overstressed leaves could not reabsorb their original water content. Ethylene emanation was in high correlation with the relative turgidity of detached leaves of oranges.

Effects of Drought Stress and Succinic Acid‐2,2‐Dimethylhydrazide Treatment on Water Relations and Photosynthesis in Pea Seedlings1

Physiological effects of drought were studied in two pea (Pisum sativum L.) cultivars to determine their relative ability to withstand this stress. Drought stress decreased dry weight and relative turgidity, reducing sugar, sucrose and starch concentrations, ribulose‐l,5‐ diphosphate carboxylase (E.CA.l.l.39) activity, and net photosynthesis in both drought‐susceptible ‘Alaska’ and drought‐resistant ‘Hardy’ peas. Decreases in dry weight, carbohydrate concentration, enzyme activity, and net photosynthesis were greater in the drought.susceptible cultlvar, but respiration rate, determined by infrared analysis, was decreased more in the tolerant cultivar. SADH (succinic acid‐2,2‐dimethylhydrazide) treatment increased relative turgidity and ribulose‐l,5‐diphosphate carboxylase activity under drought stress, but decreased respiration and rate of water uptake in both cultivars under nonstress conditions. Sucrose concentration increased in Alaska peas whereas net photosynthesis decreased in Hardy peas after SADH treatment. SADH had no effect on reducing sugar and starch concentrations. It was concluded that SADH treatment probably enabled plants to tolerate stress longer by decreasing energy requirements and metabolic degradation rates.

Rapid Estimates of Relative Water Content

Relative water content may be accurately estimated using the ratio of tissue fresh weight to tissue turgid weight, termed here relative tissue weight. That relative water content and relative tissue weight are linearly related is demonstrated algebraically. The mean value of r(2) for grapevine (Vitis vinifera L. cv. Shiraz) leaf tissue over eight separate sampling occasions was 0.993. Similarly high values were obtained for maize (Zea mays cv. Cornell M-3) (0.998) and apple (Malus sylvestris cv. Northern Spy) (0.997) using a range of leaf ages. The proposal by Downey and Miller (1971. Rapid measurements of relative turgidity in maize (Zea mays L.). New Phytol. 70: 555-560) that relative water content in maize may be estimated from water uptake was also investigated for grapevine leaves; this was found to be a less reliable estimate than that obtained with relative tissue weight. With either method, there is a need for calibration, although this could be achieved for relative tissue weight at least with only a few subsamples.

Variation in Drought Tolerance in Eucalyptus viminalis Labill

Six-month-old seedlings of two low rainfall populations of Eucalyptus viminalis showed greater resistance to desiccation and were less damaged by sustained drought than seedlings from two high rainfall populations. The more resistant seedlings did not simply avoid drought by quickly closing stomata, but were capable of maintaining relatively high rates of transpiration under moderate moisture stress. The two populations from moist habitats wilted at a higher relative turgidity of leaves than did the populations from the drier habitats. Furthermore, for populations from one dry habitat and one moist habitat, changes in relative turgidity in relation to water potential of leaves during drying were not significantly different. It is suggested that the greater tolerance of the low rainfall populations to drought is related to physiological resistance of the protoplasm to desiccation. Some differences in drought resistance were also noted between the two low rainfall populations. Young seedlings (3 months old) from a population on a deep basalt-derived soil were less resistant than young seedlings from a neighbouring population on a shallower granite soil. It is suggested that the selection for drought tolerance at the granite site has been more severe than at the basalt site.

Genetic modification of cotton plants for more efficient water use

A review of research in water-use efficiency of cotton is presented. Variability exists in numerous cultivars of cotton in fruiting pattern, rooting depth, relative turgidity at wilting point and at stomatal closure, transpiration rate, leaf area, thickness and shape, stoma frequency, and leaf resistance. Since these variables are related to water use by cotton, there is a potential for breeding more efficient cotton varieties with respect to water requirement.

Growth and Yield of Irrigated Sesame II. Effects of Population and Variety on Reproductive Growth and Seed Yield

SUMMARYFour local sesame varieties were tested at three plant populations. Increase in plant density increased seed yield, which was positively related to number of pods per plant, seeds per pod, 1000-seed weight, heights of main stems and numbers of nodes per plant. Changes in soil moisture did not affect relative turgidity, whereas stomatal openness decreased as the irrigation interval became longer.

The Physiological Effect of Water Quality and Method of Application on Tomato, Cucumber, and Pepper1

Abstract Tomatoes and cucumbers were irrigated by sprinkling and trickling, using equal quantities of water containing 800 mg Cl/liter and having an electrical conductivity of 3.6 mmho/cm. Sprinkling produced higher contents of soluble and diffusible ions, free ammonia, and free amino acids in the leaves, and reduced starch, protein, pigments, and relative turgidity. The yield of ‘Moneymaker’ tomatoes irrigated by trickling was more than double that obtained by sprinkling, while no yield at all was achieved from sprinkled ‘Marmande’ tomatoes and cucumbers. The differences in plant response between the irrigation methods seem to be the result of salinity. Pepper plants irrigated with water containing 95 mg Cl/liter and having an electrical conductivity of 0.6 mmho/cm had a higher content of soluble and diffusible ions in the leaves when irrigated by sprinkling than when irrigated by trickling. There was no difference in yield between the 2 methods.

Environmental control of apical dominance in Phaseolus vulgaris

When seedlings of Phaseolus vulgaris were grown under controlled conditions at a light intensity of 3200 ft-c, 60% relative humidity, and at nitrogen levels of 5.25, 52.5, and 210 ppm, growth of the buds at the cotyledonary node, which served as a measure of apical dominance, showed a positive correlation with the nitrogen supply and with the soluble nitrogen content of the hypocotyl. Increasing the nitrogen supply to 420 ppm caused a proportionate increase in soluble nitrogen content but no additional bud growth response. That the growth response was limited by water supply was shown by growing plants at 420 ppm nitrogen and relative humidities of 30, 60, and 90%. Each reduction in water stress, as measured by leaf relative turgidity, caused a highly significant increase in growth of the cotyledonary buds. Under high nitrogen, low water stress conditions, bud growth was markedly inhibited by reduction of the light intensity from 3200 to 700 ft-c.These results support the concept of nutrient competition as a major factor in the mechanism of apical dominance and also suggest that conflicting reports on the effect of externally applied growth-regulating substances on lateral bud inhibition may be due partly to environmentally induced differences in nutritional status of the experimental plants.

Stomatal regulation of ozone phytotoxicity in tomato

Summary Effects of pre-fumigation darkness, soil-plant-water stress and phenylmercuric acetate (PMA) on ozone-induced phytotoxicity in relation to stomatal width were investigated. Plants were protected from ozone phytotoxicity by a 3-h dark period, by dry soil condition resulting in a leaf relative turgidity of 80 %, and by a foliar application of 10−6 M PMA. Quantitative expression of such protection was evident in high chlorophyll content, and was always accompanied by a marked reduction in stomatal aperture.

Alteration of Protein Composition of Corn (Zea mays L.) Seedlings During Moisture Stress1

The rapidity and magnitude of change in nitrate reduction and assimilation, protein metabolism, and associated ribonucleic acid were investigated in corn (Zea mays L.) seedlings subjected to moisture stress. The objective of the study was to determine the sequence of events that lead to protein alteration. Nitrate reductase was highly susceptible to tissue dehydration and markedly lost activity with only slight reductions in leaf relative turgidity. Reduced protein synthesis instead of increased protease activity caused leaf protein concentration to decrease during severe moisture stress conditions. Appreciable loss of protein was not detected during mild stress. Alterations in RNA synthesis appeared to be as important as increased RNase activity in determining leaf RNA concentration during mild stress. During severe stress, however, increased RNase activity was probably more important in decreasing RNA.

Release of Plant Moisture Stress and Self‐Tripping in Alfalfa1

Two experimental clones of alfalfa (Medicago sativa L.) were vegetatively propagated and grown to flowering in a plant growth chamber. Water was withheld from some of the plants to induce plant moisture stress which was measured by the relative turgidity (R.T.) method. After visible wilting was noted, water was supplied and recovery from water stress and flower tripping were measured periodically. Wilted plants recovered in 90 minutes and approximately 70%, of all open florets on one clone tripped within 2 hours. In this clone, percent of tripping after watering was highly correlated with R.T. of the plant before watering (r = — 0.856). Plants of the second clone similarly recovered from wilting, but no tripping occurred. Tripping in some alfalfas may becaused by recovery of turgidity.

Estimating Leaf Water Content by Reflectance Measurements1

AbstractRegression equations expressing reflectance of incidentlight from the upper (adaxial) surface of single leaves as a function of their relative turgidity and water content were developed. Reflectance at the 1.45‐ and 1.93‐µ water absorption bands was significantly related (p = 0.01) to the leaf relative turgidity or water content. However, because of variations in internal leaf structure associated with the availability of water during leaf development, the ability to predict the leaf water status from reflectance easurements was poor. With cotton (Gossypium hirsutum L.) the greatest change in reflectance occurs when the relative turgidity is below 70% and the leaves are visibly wilted. Within the relative turgidity range, 70 to 80%, reflectance changes are small and may not be definable for predictive purposes because of variation among leaves of field‐grown cotton caused by age differences and osmotic stresses.

Effect of Gypsum and Drought Stress on Maize (Zea mays L). II. Consumptive Use of Water1

AbstractThe effect of three defined periods of drought stress on the consumptive use of water by field grown maize (Zea mays L.) was measured using a complete water balance approach. Water status within the crop was defined by noon measurements of relative turgidity (RT). The treatments were set out in a randomised block design with a further comparison between the untreated (sodic) soil and the same soil treated with gypsum at 22.4 m tons ha−1.The components of the water balance — soil stored moisture, rain, and applied irrigation — were measured directly, and deep drainage was calculated from chloride redistribution. The no‐stress treatment (RT at noon maintained > 90%) used 59 cm in evapotranspiration during the growing period. Drought stress (RT at noon < 90%) for a period of 20 days during male meiosis (early stress) reduced this total evapotranspiration to 44 cm, while drought stress during grain filling (late stress) reduced it to 51 cm. The application of gypsum had no significant effect on water use nor on water entry at irrigation.Application efficiency (total evapotranspiration/total applied water) was 86%, 79%, and 85% on the no‐stress, early‐stress, and late‐stress treatments respectively. The balance (15 to 20%) of applied water was lost as deep drainage, indicating that results on more permeable soils would be inaccurate if this component were ignored.Maximum water use of 0.9 cm day−1 (or 0.8 of class “A” pan) occurred during anthesis. This period was delayed 10 days by early stress. Water use efficiency was highest for the early stress‐87 kg dry grain/cm water/ha and lowest for the late stress‐26kg.

Effect of Gypsum and Drought Stress on Maize (Zea mays L.). I. Growth, Light Absorption and Yield1

AbstractAn experiment was designed to study the effect of gypsum and drought stress on growth, water status and yield with maize (Zea mays L.). Water status was assessed under field conditions by measurements of relative turgidity (RT) at noon. No stress was defined as RT greater than 90% — drought stress as RT less than 90%. A nostress crop was compared with a crop drought stressed for a period of 20 days during male meiosis and with a crop drought stressed during grain filling (after pollination to maturity). These treatments were set out in a randomised block design with a further comparison between the untreated sodic clay soil (control) and the same soil treated with gypsum.Gypsum and no‐stress conditions stimulated tiller production so that the final effective plant densities were above optimum. The no‐stress treatments produced large amounts of dry matter but this was channelled into sterile tillers rather than into grain. Drought stress during male meiosis stunted growth, stunted tassel development, reduced chlorophyll content and light absorption (during the period of stress) but, overall, was not very detrimental to grain yield. Drought stress during grain filling reduced grain yield by 50%; grain weight was reduced and a very high proportion of photosynthate went into sterile tillers.

RAPID MEASUREMENTS OF RELATIVE TURGIDITY IN MAIZE (ZEA MAYS L.)

SummaryTwo rapid methods of assessing relative turgidity in maize are described. The first involved measuring the water uptake by discs of leaf tissue but omits the oven dry weight from the calculation. Where the position on the leaf was standardized, the relationship was linear (r = 0.99***) over a wider range than normally encountered in field conditions. The regression relationship held for plants grown under a wide variety of environmental conditions and at various stages of development.The second method utilized a series of photographic standards of plants at different relative turgidities. Relative turgidity could then be estimated visually by comparing the plant and the photographic standards.Accuracy with either method was similar to the experimental error of relative turgidity measured by normal means. Both offer a considerable saving in time, especially the photographic standard method which allows instantaneous readings to be made. This should permit field workers to assess rapidly the water status of their crop without the labour involved in conventional measurements.

Water Use by Maize at Three Plant Densities

SUMMARYWater use by maize at three densities was measured by a complete water balance, including soil moisture, rain, applied irrigation and deep drainage in crops irrigated so that relative turgidity at noon remained above 90 per cent (i.e. no-stress conditions). Total evapotranspiration between planting and harvest, 56 cm., was not significantly affected by density, but evapotranspiration was slightly higher at higher densities when ground cover was less than 50 per cent. Actual evapotranspiration rose to 1 cm. per day during anthesis and grain filling. A fifth of the water applied moved beyond the root zone, indicating that work on more permeable soils would be inaccurate if the deep drainage component was ignored.

The Early Stages of Grain Development in Wheat: Response to Water Stress in a Single Variety

In wheat (Triticum ae8tivum cv. Gabo) a temporary water deficit in the first 7 days following anthesis significantly reduced the final grain weight per ear. A reduction in seed set in response to stress was associated with an initially greater rate of development of the remaining grains, with an enhanced rate of cell division in the endosperm. Relative turgidity measurements indicated that the stress applied did not significantly reduce grain water content, although the ear structure showed some water loss, and the stem and flag leaf blade were quite severely stressed. Th!' greater desiccation of the leaf and stem in comparison with the ear was reflected in the lower rate of photosynthesis of these organs under stress conditions.

Temperature Effect of Greenhouse Water on Rose and Chrysanthemum Turgidity, Stomate Behavior, Growth, and Flowering1

Abstract Cold irrigation water during mid-winter significantly reduced greenhouse soil temperatures, reduced rose and chrysanthemum relative turgidities, tended to partially or completely close stomates and decreased plant heights and fresh weights. Rose and chrysanthemum leaf relative turgidities were found to decrease from 86% and 79% before irrigation with 35°F water to 54% and 43% one hour after watering. Scanning electron micrographs of rose and chrysanthemum leaves were used to compare stomates during a 5 hour period after irrigation with 35°F and 65°F water. Photographs showed 35°F water caused stomates to close, produced a pronounced flaccidity of guard cells and caused considerable distortion of leaf epidermal cells within 1 to 2½ hours after its application. Chrysanthemum plant heights and fresh weights at flowering decreased significantly as irrigation water temperatures declined. No treatment differences in numbers of rose flowers were found, but stem lengths and fresh weights were reduced significantly.

Water Deficit Effects on Corn. I. Vegetative Components1

AbstractCorn was grown in large buried containers and stressed nonrepetitively by cessation of irrigation at nine different times during the season. Each stress treatment consisted of 4 days on which the uppermost, fully‐expanded leaves were wilted. Water status of the yield plants was estimated in terms of the relative turgidity (RT) of like‐treated plants, soil moisture and other environmental factors. Vegetative component yields were determined in two experiments, the first including the additional factor of limiting soil fertility. Each component was significantly influenced by one or more of the stress periods. Maximum reductions in total vegetative dry matter production of 15 to 17% resulted from water deficits approximately 3 weeks before 75% silking. Significant increases in stalk weight occurred as a result of stress at late silking and very early ear stages.