Genetic control of the mitochondrial form of superoxide dismutase in hexaploid wheat

Extracts of mature grains of a large number of aneuploid derivatives of Triticum aestivum cv. Chinese Spring and of the members of five wheat-alien chromosome addition series were subjected to isoelectric focusing in polyacrylamide gels in order to study the genetic control of superoxide dismutase (SOD). Evidence was obtained that homologous structural genes for the mitochondrial form of SOD are located in the long arms of the homoeologous group 2 chromosomes of Chinese Spring and in chromosome 2R of Secale cereale cv. Imperial. The SOD gene loci located in chromosomes 2A, 2B, 2D, and 2R were designated Sod-A1, Sod-B1, Sod-D1, and Sod-R1, respectively. Chromosome-arm pairing data indicate that 2DL is not homoeologous to either 2AS or 2BL. The results of this study suggest, however, that 2BL is partially homoeologous to both 2AL and 2DL.Technical article No. 21074 of the Texas Agricultural Experiment Station. This work was supported by USDA Grant 83-CRCR-1-1322 to GEH.     

A burst of CO2 from photosynthesizing leaves after a temperature decrease under constant light conditions

A transient CO₂ burst from seedlings of some plant species was observed after a rapid temperature decrease. The magnitude of the CO₂ release depended on initial temperature, oxygen concentration and light intensity. To obtain a maximal value of CO₂ release, the temperature had to decrease by more than 8°C. The phenomenon was detected only in the light, and was confined to C₃ species. It was inhibited by low oxygen concentration, indicating its possible connection with photorespiration.     

The place of brassinolide in the sequential response to plant growth regulators in elongating tissue

In the sequential response to plant growth regulators in young elongating tissue from peas and wheat the peak of sensitivity to 24-epi-brussinolide (1 μM) occurs after those of gibberellin and cytokinin and begins before that of auxin in isolated wheat ( Triticum vulgare L. ev. Egret) coleoptiles aged from 21-96 h. In dwarf pea ( Pisum sativum L. cv. Greenfeast) segments, the peak of sensitivity also lies between those of gibberellin and auxin, and it also occurs before sensitivity to auxin in sections from first leaves of wheat. All the leaf sections and all but the most mature coleoptiles and pea segments were sensitive to fusicocein (1 μM).     

Influence of washing on elemental analysis of leaves of fieldgrown crop plants

Summary Information is limited on soil contamination of leaves from field-grown row crops, especially with respect to aluminum (Al) analyses. The objective of this study was to determine the influence of washing leaf samples with either deionized water or detergent solution on elemental analyses for several agronomic crop plants. The crop plants sampled were corn (Zea mays L.), soybean (Glycine max L. Merr.), grain sorghum (Sorghum bicolor L. Moench), and wheat (Triticum aestivum L.). The crops were grown on a range of soil types, soil pH values, and tillage practices. Samples of upper leaves and lower leaves were collected separately. The samples were either not washed, washed with deionized water, or washed with detergent solution. After drying, grinding, and digesting, the samples were analyzed for Al, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu). For all crop plants and conditions studied, there was no effect on measured N, P, K, Ca, Mg, Mn, Zn, or Cu concentrations, but measured Al and Fe concentrations were influenced by washing. In general, washing had a greater effect on Al analyses than on Fe analyses. Soybean samples were most affected by washing, while wheat samples seemed to be least affected. The results reflected greater contamination of lower leaves than upper leaves. Decontamination procedures appear necessary prior to Al and Fe analyses of field-grown crop plants.     

Betaine status in wheat in relation to nitrogen stress and to transient salinity stress

Summary Glycine betaine is readily accumulated in wheat (Triticum aestivum cv. Inia) shoots during periods of salinity stress. The ability of the plant to utilize betaine as a source of nitrogen remains unresolved. We, therefore, conducted solution culture experiments in a greenhouse to test the hypothesis that betaine is degraded in wheat shoots under conditions of severe nitrogen deficiency. Betaine concentrations increased in continuously salt stressed plants for only 17 days after salinity was imposed. After this period, concentrations (dry weight basis) decreased steadily until plants died 32 days later. Decreases in betaine concentration were also observed in treatments where salinity stress was removed. The rate of decrease in concentration was greatest in the N-free treatment. These decreases in betaine concentration were the result of dilution by plant growth. Betaine contents (mol shoot^–1) remained unchanged after removal of substrate nitrate. Therefore our results support the hypothesis that betaine is a stable end product of metabolism.     

Pressure chamber measurements using two wheat leaves

Summary The most widely used technique of leaf water potential measurements is with the Scholander pressure chamber. Representative leaf water potential values require many determinations on individual leaves and this can be time consuming in large fields or experiments with multiple treatments. This paper describes a method of obtaining a mean value more rapidly, by using two leaves in the pressure chamber at the same time, but recording the end point of each leaf separately.     

Free proline accumulation in drought-stressed plants

Summary Free-proline accumulation was measured in leaves of intact wheat (Triticum vulgare L. cv. Kalyan Sona), plantago (Plantago ovata Forsk-Isabgool), papavar (Papaver somnifera L. Opium poppy) and mustard (Brassica juncea L. var. Varuna) grown in the field with low to high field water content and thus they were subjected to water stress. Leaf water deficit in percentage was used to determine the degree of stress at the time of proline anlysis.Free proline content was higher in mustard leaves as compared to wheat, plantago and papavar leaves. Water stress enhances the proline content but at same water deficit level the content differ in the leaves of the plants studied.     

Genetic control of endosperm proteins in wheat

Summary Total endosperm proteins extracted from both several common wheat cultivars and some intervarietal substitution lines derived from them were fractionated according to their molecular weight in a high resolution one-dimensional gel electrophoresis. The four donor cultivars and the recipient one — Chinese Spring, possessed differentially migrating protein bands in the fractions of high molecular weight (HMW) glutenins and gliadins. Several of these bands were identified for the first time in this study. By utilizing intervarietal substitution lines the control of the HMW glutenins and gliadins by chromosomes of homoeologous group 1 was either reaffirmed or, for the new bands, established. Several HMW gliadin subunits showed a considerable variation in their staining intensity in the intervarietal substitution lines indicating that their expression was dependent on the genetic background.This paper is based on a portion of a dissertation to be submitted by G. Galili in partial fulfilment of the Ph.D. requirements of the Feinberg Graduate School, The Weizmann Institute of Science, RehovotThe Marshall and Edith Korshak Professor of Plant Cytogenetics     

Relative efficiency of two mating systems and selection procedures for yield improvement in wheat (Triticum aestivum L.)

Summary The relative efficiences of the biparental mating systems and selfing series in connection with phenotypic and geno-phenotypic selection procedures were evaluated for yield improvement in a cross HP1102 X CPAN 1681 of wheat. Two selection cycles having a 4 per cent selection intensity for grain yield were carried out following both selection procedures under the two mating systems. Following these selection procedures, a greater improvement for grain yield could be achieved with the biparental mating system than with the selfing series. During the first selection cycle, the geno-phenotypic selection procedure had an edge over phenotypic selection procedure. The realized response due to the second cycle of selection and the predicted response for the third selection cycle indicated that the phenotypic selection procedure is more efficient than the geno-phenotypic selection procedure. It is suggested that selection following intermating in early segregating generations is able to overcome several inherent limitations of the simple pedigree method as it is possible to increase genetic variation and to concentrate favourable genes and gene combinations for grain yield. An increase in grain yield was, in general, accompanied by an increase in plant height, peduncle length, 100 grain weight, tiller number and biological yield. Therefore, it is suggested that an index comprised of grain yield, plant height, tiller number, grain weight and biological yield could be used for selecting high yielding genotypes of suitable height.