A. Marani

Modelling diurnal patterns of air temperature, radiation wind speed and relative humidity by equations from daily characteristics

Abstract Calculated data on diurnal patterns from daily averages can be useful as inputs for models simulating plant processes such as photosynthesis and transpiration. A method was developed for the calculation of diurnal patterns of air temperature, wind speed, global radiation and relative humidity from available daily data. Calculated data were validated with measured data collected in Israel, California and The Netherlands. A simple sine-exponential method for describing diurnal air temperature was not sufficient in most cases, and the addition of parameters which specified the time lag of maximum temperature and the effect of buoyancy improved the data accuracy. Diurnal course of wind speed could be described using two sine curves scaled by the measured daily total wind run. Time base of each of the sine curves and the minimum wind speed had to be defined for each location. An accurate description of the diurnal global radiation was obtained, based on the measured daily total global radiation, and the calculated sine of the solar elevation corrected for atmospheric transmissivity. Relative humidity was calculated from the dew point temperature computed as the minimum value of a characteristic seasonal value or the actual air temperature. When the site-specific parameters were known or correctly estimated these methods gave good estimations of the diurnal weather patterns.

Breeding tomatoes for salt tolerance: inheritance of salt tolerance and related traits in interspecific populations

SummaryInterspecific segregating populations derived from a cross between tomato (Lycopersicon esculentum) cv ‘M82-1 -8’ (M82) and the wild species L. pennellii accession LA-716 (Lpen716) were used to study the genetic basis of salt tolerance and its implications for breeding. BC1 (M82 x (M82 x Lpen716)) and BC1 S1 (progenies of selfed BC1 plants) populations were grown under arid field conditions and irrigated with water having electrical conductivities of 1.5 (control), 10 and 20 dSm-1. The evaluation of salt tolerance was based on total fruit yield (TY), total dry matter (TD) and TD under salinity relative to the control (RD). Sodium, potassium and chloride concentrations were measured in the leaves and stems. The methods for estimating heritability were adapted to BC1 plants and BC1S1 families. TY, TD and RD had heritability estimates of 0.3–0.45, indicating that salt tolerance can be improved by selection. Genetic correlations between traits indicated that high yield may be combined with salt tolerance and that ion contents are not likely to provide an efficient selection criteria for salt tolerance. Genetic correlations between performances under various salinity levels suggested that similar mechanisms affect the responses to salinity treatments of 10 and 20 dSm-1. Responses to “paper” selection confirmed that salt tolerance of the tomato may be improved by selection, and that this selection should be based on dry matter and yield parameters under salinity.

Effects of moisture stress on stomatal resistance and photosynthetic rate in cotton (Gossypium hirsutum). 1. Controlled levels of stress.

Abstract The effects of moisture stress on stomatal resistance and on photosynthetic rate were studied in cotton ( Gossypium hirsutum L., cv. Acala SJ-2) under field conditions with drip irrigation in 1984 and in 1985. Moisture stress was evaluated by measuring the minimum midday leaf water-potential, which was kept at two levels (−1.6 and −2.4 MPa) during each of two phenological periods. Stomatal resistance increased and photosynthetic rate decreased as a result of moisture stress. The correlation between stomatal resistance and radiation was lower when the plants were subjected to moisture stress. An exponential asymptotic relationship was found between photosynthetic rate and stomatal resistance. Stomata were found to limit the photosynthetic process in well-watered plants or in midly stressed plants, while mesophyll resistance was the main factor reducing it under more severe moisture stress. In the moisture-stressed plants, mesophyll resistance increased more than did stomatal resistance, and this was associated with a higher internal CO 2 concentration in the leaf ( C i ) and a lower ratio of photosynthetic rate to C i . Under moderate moisture stress the maximum photosynthetic rate was attained at an earlier leaf age, while a more severe stress resulted in a lower photosynthetic rate at all leaf ages.

Wheat Disease Control Advisory, a decision support system for management of foliar diseases of wheat in Israel

Wheat disease control advisory (WDCA), a computerized decision support system for managing septoria tritici blotch, leaf rust, and yellow rust, was developed and field tested under the semi-arid conditions of Israel. The system operates on a persona] computer and thus can be managed independently at any time by the user. During the decision making procedure, the system considers economic, agronomic, phytopathological and both recorded and forecast weather. It analyzes the effects of these factors on the benefits of disease control and provides a recommendation for action to suppress these diseases efficiently. WDCA was tested over 4 years in 81 field experiments by its developers and by commercial growers. In plots managed according to WDCA, a significant increase of 0.78 t/ha in yield, or US

Growth and NPK uptake of high-yielding cotton grown at different nitrogen levels in a permanent-plot experiment

92.70 per ha in net profit, was obtained relative to the common management policy. The knowledge base used for constructing WDCA, its decision making process, the technology transfer techniques, the validation proc...

A prediction of developmental stages in potato plants based on the accumulation of heat units

Growth and N, P, K uptake of Acala SJ-2 cotton (Gossypium hirsutum) were investigated in an irrigated permanent-plot field (Typic chromoxerert) at Bet Dagan, Israel, under semi-arid conditions using different nitrogen levels: 0, 60, 120, 180 and 240 kg N ha−1. The total dry matter accumulation at these levels was 9.0, 10.7, 15.1, 17.1 and 15.6 ton ha−1, respectively. The uptake of N, P and K was 110, 144, 267, 322 and 301 kg N ha−1∶31, 34, 46, 44 and 38 kg P ha−1; and 120, 151, 208, 251 and 230 kg K ha−1, respectively.Dry matter production, as well as N, P, K uptake by the cotton plants were greatly increased by raising the N application levels to 120 or 180 kg N ha−1, but the pattern of accumulation and relative distribution of dry matter and NPK among plant organs were not considerably affected.

Growth rate of cotton bolls and their components

Abstract Growth of potato plants (cv. Desiree) was analyzed over a seven-year period in commercial fields at two locations, during Israels two growing seasons. The effect of temperature on developmental rate was studied to determine the appropriate heat-unit model for predicting dates of tuber appearance, and termination of the yield-bulking period. The best prediction of tuber appearance date was based on the accumulation of heat units calculated using a linear relationship between developmental rate and daily mean temperature with a combination of 2°C-25°C-35°C for threshold, optimum and maximum temperatures, respectively. Predictions of bulking cessation based on several reported models were not any more accurate than predictions based on the accumulation of chronological days. High temperatures were found to negatively affect the developmental rate at both developmental stages. However our analyses indicate that the maximum temperature for tuber appearance is higher than that reported previously.

The relations between leaf water potential of cotton plants and environmental and plant factors

Abstract The growth rate of cotton, Gossypium hirsutum L., bolls was investigated at three locations in the Coastal Plain of Israel. Random samples of bolls that had been tagged at anthesis were periodically taken. Burs and seed-cotton were weighed separately, after being dried, for each boll. The weight of the two heaviest bolls in each sample was taken as ‘potential weight’, and a temperature-dependent time-scale was used. It was found that the potential growth of whole cotton bolls may be modelled by using the following assumptions: (a) seed-cotton dry-weight follows a sigmoid function; (b) bur dry weight grows linearly during 21 days, with no further growth later on; (c) there is a maximum rate of boll growth with priority to seed-cotton, causing a decrease in bur dry weight during peak seed-cotton growth. Parameters for the cultivar Acala SJ-1 were calculated by fitting the functions to the observed data. Average boll weight was only 0.65-0.85 of the potential weight, probably because of stresses affecting whole plants or sites of individual bolls.

Effects of Soil Moisture Stress on Two Varieties of Upland Cotton in Israel IV. Effects of Periods of Stress Occurrence, Correlations and Regressions

Abstract An equation for calculating leaf water potential (Ψ1) of cotton (Gossypium hirsutum L.) plants, based on environmental and plant factors, was developed. Two irrigation experiments were conducted with cotton (cv. Acala SJ-2), on a loamy clay soil. Data from 18 treatments of one experiment were pooled and used for multiple regression analysis with Ψ1 as the dependent variable. The parameter displaying the highest correlation with Ψ1 was the reciprocal of the relative soil water content in the upper 105 cm of the soil profile. A regression equation combining this factor with air temperature, an index indicating the crops water stress history and plant height explained 87% of the variation in Ψ1. The Ψ1 calculated by using this equation showed good correspondence (r = 0.9) with data from eight distinct irrigation treatments of the other experiment. It was shown that Ψ1 of cotton plants can be reliably calculated based on some readily available variables.

Simulation of the effect of drought stress on the rate of photosynthesis in cotton

Effects of moisture stress during different stages of cotton development were evaluated by using correlation and regression methods on data of six irrigation experiments from three different climatic regions. Significant negative correlations were found between the number of days in which soil moisture was below a threshold level, and several plant traits. Flower number was usually affected adversely by stress at the beginning of flowering; boll number, boll retention, boll weight, lint yield, lint length and seed index by stress at the end of flowering; earliness and lint fineness by stress during early boll development. Lint index, per cent and strength were affected by stress at different periods and effects of stress on lint yield were correlated with its effects on boll number, boll weight, lint length and early maturity.