Pollen grains of heat tolerant tomato cultivars retain higher carbohydrate concentration under heat stress conditions

Exposure to high temperatures (heat stress) causes reduced yield in tomatoes (Lycopersicon esculentum), mainly by affecting male gametophyte development. Two experiments were conducted where several tomato cultivars were grown under heat stress, in growth chambers (day/night temperatures of 31/25 °C) or in greenhouses (day/night temperatures of 32/26 °C), or under control (day/night temperatures of 28/22 °C) conditions. In heat-sensitive cultivars, heat stress caused a reduction in the number of pollen grains, impaired their viability and germinability, caused reduced fruit set and markedly reduced the numbers of seeds per fruit. In the heat-tolerant cultivars, however, the number and quality of pollen grains, the number of fruits and the number of seeds per fruit were less affected by high temperatures. In all the heat-sensitive cultivars, the heat-stress conditions caused a marked reduction in starch concentration in the developing pollen grains at 3 days before anthesis, and a parallel decrease in the total soluble sugar concentration in the mature pollen, whereas in the four heat-tolerant cultivars tested, starch accumulation at 3 days before anthesis and soluble sugar concentration at anthesis were not affected by heat stress. These results indicate that the carbohydrate content of developing and mature tomato pollen grains may be an important factor in determining pollen quality, and suggest that heat-tolerant cultivars have a mechanism for maintaining the appropriate carbohydrate content under heat stress.     

Quantitative method of inoculation of celery plants withSeptoria apiicola

Celery (Apium graveolens L.) plants were inoculated with 3-µl droplets of a pycnidiospore suspension ofSeptoria apiicola Speg., and then covered with polyethylene bags and kept at an ambient temperature of 23±2°C. Under these conditions disease expression was related to incubation time up to 8 days, and to spore concentrations up to 500/3 µl. An inoculum concentration as low as four viable spores per 3 µl caused 26% as many lesions as did 500 spores/3 µl. In plants not covered, or covered with polyethylene bags for only 1 day, no disease symptoms appeared regardless of the spore concentration applied to the plants. Disease symptoms on inoculated leaves appeared on 10-50-day-old but not on 50-90-day-old leaves. The pathogenicity of 16 isolates collected from two different regions of Israel, and of eight replicates of an isolate used in previous pathogenicity tests, was similar.     

EFFECT OF MERTHIOLATE (LILLY) ON CERTAIN SPECIFIC PRECIPITATION REACTIONS

Merthiolate (Lilly), a substituted benzoic acid, has been shown to interfere, in concentrations usually used for preservation, with the specific precipitation of antisera against beef serum or sheep serum coupled with diazotized p-aminobenzoic acid, p-arsanilic acid, or p-(p-aminophenylazo) phenylarsonic acid. In some systems increased precipitation was observed, while in others decreased precipitation was observed.     

Combined effects of KNO3 and salinity on yield and chemical composition of lettuce and Chinese cabbage

Summary The effect of N and K nutrition on the salt tolerance of lettuce (Lactuca saliva L. cv. Saunas) and Chinese cabbage (Brassica campestris L., Pekinensis cv. Kazumi) was evaluated in three greenhouse experiments under a controlled aero-hydroponic system of cultivation. Three levels of KNO₃ (1, 5 and 10 mM) were tested in all the experiments with rapidly circulated saline and nonsaline nutrient solutions. Two experiments, carried out between January and March 1989, with lettuce (Exp. I) and Chinese cabbage plants (Exp. III), consisted of two salinity levels, EC = 1.75 and 6.0 dS m^–1, the former representing a nonsaline nutrient solution. In the third experiment with lettuce (Exp. II., conducted between March and May 1989), three saline nutrient solutions having EC levels of 4.7, 7.75 and 10.75 dS m^–1 were compared to the nonsaline solution. The nutrient solutions were salinized with NaCl and CaCl₂, in a 4:1 molar ratio. The highest yields of fresh weight of both crops were obtained from the 5 mM KNO₃ under both saline and non-saline conditions. The 10 mM treatment caused yield reduction in Chinese cabbage, probably due to a severe tipburn disorder. The relatively high fresh weight yield obtained at the lowest (1 mM) KNO₃ level can be explained by the positive effect of circulation velocity on nutrient uptake. The threshold salinity damage value for the vegetative yield of lettuce plants fed by 5 or 10 mM KNO₃ was approximately 5 dSm^–1 and the yield decreased by 6.5% per unit dS m^–1 above the threshold. No yield improvement due to the addition of KNO₃ occurred under highly saline conditions (Exp. II). The fresh weight of Chinese cabbage obtained from the saline 1 and 5 mM KNO₃ treatments was approximately 15% lower than the non-saline-treatment (Exp. III). Salinity increased tipburn and the effect was not altered by the addition of KNO₃. No significant interaction between nutrition (KNO₃ level) and salinity was found. The application of salts increased the concentration of Na and Cl in plant tissue and reduced the levels of N and K; the opposite occurred in plants fed by the medium and high levels of KNO₃.Contribution from Institute of Soils and Water, ARO, Volcani Center, PO Box 6, Bet Dagan 50250, Israel. No. 3092-E 1990 series     

Immunoglobulin M antibodies with ten combining sites

Immunoglobulin M rabbit antibodies to a hapten are shown to have ten binding sites per molecule. The affinity for the specific hapten is approximately 100 times greater for one-half of the sites than for the other half. All sites are retained in the five 7S subunits produced by reduction and alkylation of the immunoglobulin M. Each of the 7S subunits of the IgM molecule apparently has one strong and one weak site.     

Interaction with salinity of GA3-induced leaf elongation,petiole pithiness and bolting in celery

GA₃ sprayed on celery plants, which received a continuous supply of 0, 0.2, 0.4, 0.6 or 1.0% NaCl solutions to the roots, caused a pronounced increase in leaf elongation.Along with enhanced elongation, GA₃ increased breakdown of parenchymatous tissue in the petiole, but this effect was drastically suppressed in the salt-treated plants. In a similar fashion, the effect of GA₃ on the elongation of the flowering-stem (bolting) was significantly diminished in salt-treated plants. In no case did the salinity treatment totally abolish the bolting-process induced by GA₃.Changing the temperature of the lower part of the root system altered the magnitude of GA₃ effect on bolting. As the temperature was lowered from 30 to 6° C, the ability of GA₃ to cause bolting was greatly reduced.The results are discussed in view of the possible interaction between salinity and the GA₃ effect on petiole elongation, cellular breakdown and bolting.     

Specific binding activity of isolated light chains of antibodies

Free light chains isolated from specifically purified antibody have been shown to bind specific hapten. This proves that part of the binding site does exist on the light chain. The light chains were obtained from antibody directed against the 4-azonaphthalene-1-sulfonate group, and the binding of the simple hapten 4-anilinonaphthalene-1-sulfonate was determined by the fluorescence-enhancement technique. Since this hapten undergoes a striking increase in fluorescence on binding to light chains (and also on binding to specific antibody), the presence of small amounts of bound hapten could be determined, even in the presence of the high concentrations of unbound hapten required because of the low binding constant.