Measurement Of Plant Water Status Research Articles

Drought resistance in spring wheat cultivars. I. Grain yield responses

With a view to understanding the basis of cultivar differences in yield under drought, a wide range of cereal cultivars representing durum wheats (Triticum turgidum L.), triticales (X Tritosecale Wittmack), barleys (Hordeum vulgare), and especially tall and dwarf bread wheats (T. aestivum L.) were studied in field experiments in north-western Mexico over three seasons. Drought was created in this rain-free environment by permanently terminating irrigation at various stages before anthesis. Control treatments were well watered throughout the growing period. Detailed measurements of plant water status, leaf area and dry matter production, anthesis date, yield components and grain yield were made. This paper presents primarily the grain yield data. Drought levels were such that the mean yield of all cultivars under drought ranged from 37 to 86% of control yield, corresponding to irrigation cut-offs varying from 69 days before mean anthesis date to only 10 days before. In each experiment the grain yield under drought showed highly significant cultivar differences, which appeared consistent between years. Yields were adjusted for drought escape by using a correction factor which ranged from 2.9 to 8.5 g/m2 per day advance in flowering, being greater in experiments with less severe drought. The demonstration of linear relationships between cultivar yield and drought intensity, as indicated by the mean yield of some or all cultivars, prompted the consideration of cultivar yield under drought as the function of yield potential (Yp, yield without drought), drought susceptibility index (S), and intensity of drought. The cultivar groups showing lowest S values (most droughtresistant) were tall bread wheats and barleys; dwarf bread wheats were intermediate, and durum wheats and triticales were the most susceptible. However, because dwarf wheats have a higher yield potential (Yp) than tall bread wheats, it is suggested that, as a group, tall bread wheats would outyield dwarf wheats only under very severe drought. Also there was considerable within-group variability of S and Yp. Cultivar S values were consistent across experiments. Yield responses of tall and dwarf bread wheat groups obtained in these experiments agreed with those seen in extensive international trials under dryland conditions.

Estimating Relative Leaf Water Content with a Simple Beta Gauge Calibration1

AbstractExisting methods for periodically measuring plant water status require considerable instrumentation or time. The method described herein simplifies plant water measurement by providing a completely linear calibration between attenuated beta radiation through a plant leaf and its relative water content simply by measuring the radiation intensity through the leaf at only two water contents — full turgidity and complete dryness. A 14C beta source was used with leaf discs from sugar beets (Beta vulgaris L.). The method includes a means for drying the leaf discs while maintaining the original geometry. Measurements on leaf discs at relative water contents between O and 1 show that the method is accurate, and that a calibration can be established using a standard method to ensure full turgidity and complete dryness without the added necessity of determining the mass of the leaf. Thus, after proper calibration, only radiation intensity measurements are required to determine the relative water content of a leaf.

Internal Water Balance of Brigalow (Acacia harpophylla F. Muell.) Under Natural Conditions

On one day each month over a period of 2½ years, diurnal measurements of plant water status, leaf diffusive resistance, carbon uptake, irradiance, ambient temperature and humidity were made in a brigalow community. Diurnal changes in leaf diffusive resistance, osmotic potential, plant water potential, and carbon uptake are shown to follow general patterns and the changes in plant water potential were related to the dawn value of plant water potential. The data suggest the development of negative turgor in brigalow and demonstrate the capacity of the plant to maintain high tissue water contents at low water potentials. Measurements of shoot extension and litter fall showed that litter fall occurred principally following shoot extension.

Simultaneous Measurements of Solution Absorption, Transpiration, Relative Plant Water Content and Growth1

AbstractInstrumentation is described for the frequent and simultaneous measurement of solution absorption and relative green weight of large individual plants from which transpiration, relative plant water content, and plant growth are calculated. The method is sensitive, nondestructive, and most useful when used in connection with an automatic digital data acquisition system. The system is ideal for monitoring the dynamics of the water status of a large living plant. Measurements made on cotton plants are presented.Relative plant water content (RPWC), defined as the ratio of relative plant green weight at time of interest to that just prior to lights‐on, corrected for accumulated CO2 assimilation, was found to be a good measure of plant water status. Resolution of RPWC is at least 10 times better than leaf density measurements made with beta‐gauging techniques. The measurement is instantaneous and can be repeated as often as desired.

Plant Water Relations, Irrigation Management and Crop Yield

SummaryResponses of crop yield to water stress are classified on the basis of physiological considerations. Crop growth is sensitive to water stress, particularly because of the physiological effects of stress on the production and maintenance of photosynthetic tissue. Crop yield, depending on the nature of the harvested organ and the origin of its constituents, may be more or less sensitive to water stress than crop growth. In applying this information to irrigation management, there is a need for simple quantitative measures of plant water status. The problem of avoiding water stress during critical ontogenetic stages and, conversely, the possibility of using moderate water stress at certain times to improve yield and the efficiency of water usage, are discussed.