The effect of soil moisture tension and nitrogen supply on nitrate reduction and accumulation in wheat seedlings

Summary The effect of soil moisture tension on nitrate reductase and on nitrate accumulation in wheat plants was studied. Nitrate reductase activity was inhibited when soil moisture tension was increased to about 3.0 bars associated with a drop in leaf relative water content to about 90 per cent. The decrease in nitrate reductase activity did not result in nitrate accumulation in short-term experiments (10 days) when plants were exposed to only 1–2 cycles of elevated soil moisture tensions. However, when the period of different moisture regimes was extended up to the flag-leaf stage, nitrate accumulated in stressed plants.Significant increase in plant nitrate concentration as a result of increased moisture tensions was only found at the high levels of added nitrogen. On the other hand, moisture tensions had no effect on the content of total nitrogen in wheat shoots, implying that nitrate reduction was rather limiting under stress conditions.An effect of soil moisture tension and nitrogen nutrition on dry matter production by wheat seedlings was also found in the long-term experiment. At the highest dose of soil nitrogen an increase in maximal soil moisture tension from 0.1 to 0.33 bars reduced plant growth; at intermediate nitrogen doses only tension higher than 2 bars reduced growth. Under complete nitrogen deficiency, plant dry matter production was very low and was not affected by soil moisture tensions.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1972 Series, No. 2185-E.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1972 Series, No. 2185-E.     

THE NUMBER OF ASSESSORS REQUIRED FOR TASTE PANELS

Consideration of the difference in taste between two samplesas a variable leads to estimates of variance. Any minimum differencein taste scores can be detected if a large enough number ofassessors is used. ^* Contribution from the Agricultural Research Organization,The Volcani Center, Bet Dagan, Israel. 1976 Series, No. 271-E.     

Estimation of available potassium for cotton by soil analysis

Measurements of exchangeable K, percentage of exchangeable K of the total exchange capacity (EPP), K extracted in a CaCl₂ solution, and the change in free-energy of exchange of K for Ca+Mg (F), were compared as methods for estimation of available K in soil for growing irrigated cotton. A significant correlation was found between each of the methods and the response to K fertilizer. The different methods are discussed; the advantages of extraction with CaCl₂ solution are that it reflects the change in free energy and is easy to operate. For sandy soils, it is suggested that determination of exchangeable K be added.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1975 Series, No. 202-E Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1975 Series, No. 202-E     

Seasonal changes in symbiotic nitrogen fixation and haemoglobin content in nodules of peanuts

Summary Seasonal fluctuations of haemoglobin (Hb) concentration in nodules and the percentage of nitrogen (N) in leaflets of rhizobium-inoculated peanuts from various planting dates, were studied under field conditions.In peanuts planted in the usual season (April, May), no correlation was found between the N and Hb concentrations during the early stages of peanut growth; however, there was a very significant correlation at later periods of plant growth. With July (out-of-season) planting there was no correlation between the Hb and N concentrations at any time.The possibility of evaluating the atmospheric nitrogen (N₂) fixation rate of peanut plants under field conditions by means of Hb and N determinations was studied.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. 1972 Series, no. 2213-E.     

COMPARISON OF DISCRIMINATION ABILITY BETWEEN TASTE PANEL ASSESSORS

Expanded tables are presented for the selection of assessorsfor taste panels. These tables may also be used for comparingthe assessors' discrimination ability, after the panel sessionshave been completed. ^*Contribution from the Agricultural Research Organization, TheVolcani Center, Bet Dagan, Israel. 1976 Series, No. 159-E.     

Effect of gibberellic acid on flowering and the thebaine yield of different clones of Papaver bracteatum

Two foliar applications of gibberellic acid (GA₃, 250 mg l^–1) enhanced the flowering in various clones of Papaver bracteatum. The most pronounced effects were obtained in late flowering clones in which GA₃ increased significantly the number and weight of the capsules and thebaine yield per plant.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No. 1267-E, 1984 series.     

The effect of growth hormones on bananas: A review

An attempt has been made to compile the knowledge from the available literature. The growth regulators reviewed include auxins, gibberellins, cytokinins, ethephon, CCC, Alar, ABA, morphactin and TIBA. None of them is used routinely. The chlorophenoxy and naphthalene compounds are definitely harmful. All others discussed are worthy of further study.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 593-E, 1982 series.     

Relation between catalase activity and fungal survival in lemon fruit infected by Phytophthora citrophthora

In lemon fruit inoculated with Phytophthora citrophthora, a continuous increase in H₂O₂ during the incubation and rot development periods was found at the infection site; seven to ten days after inoculation of the fungus, the mycelium and fruit cells were dead. The suggestion is made that the increase in H₂O₂ may be related to the decrease in catalase activity and be responsible for the death of the fungus and fruit cells.The effect of different concentrations of peroxide on the fungus in-vitro was tested.Contribution from the Volcani Center, Agricultural Research Organisation, Bet Dagan, Israel. 1974 Series, No. 104-E. Division of fruit and Vegetable Storage, Bet Dagan 50 200, Israel/     

Using forage crops to reduce nitrate accumulation in hula peat soils

Summary A two-year field experiment was made of growing Rhodes grass and alfalfa on peat soil of the Hula Valley, where high nitrate accumulation occurs under row crops or plantless soil and leads to the danger of contamination of Lake Kinneret. The aime of the investigation was to use these perennial high-nitrogen-consumer crops to prevent the nitrate accumulation in the peat soil. The results showed a drastic decrease in soil N-NO₃ under both species in two irrigation systems obtaining high dry matter yields with high plant nitrogen content without the use of any nitrogen fertilizer. Contribution from The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel. 1977 series, no.263-E.     

Studies on fertilization of field-grown irrigated alfalfa

Alfalfa (Medicago sativa L.) yields of 20–25 ton/ha are obtainable in a Mediterranean climate, with 8–9 harvests each year. These high yields demand a large supply of potassium from the soil. Plant uptake of potassium reached 540 kg K ha, the majority being derived from the exchangeable form. A safety level of 2.5% K in the whole plant is needed to prevent yield declines. Fertilization with potassium chloride gave higher yields than with potassium sulfate. Splitting the K application over period of two cuts is recommended for sandy loam soils with a low cation exchange capacity.Contribution from the Agricultura Research Organization, The Volcani Center, Bet Dagan, Israel. 1975 Series, No.186-E.     

Evaluation of isozyme systems in Citrus to facilitate identification of fusion products

Summary Ten isozymes were analyzed in nucellar calli of nine Citrus species and cultivars and roots of the corresponding apomictic seedlings. The zymograms obtained can be divided into three groups: a) isozyme patterns similar in both calli and roots, b) isozyme patterns similar in calli but variable in roots, and c) isozyme patterns variable in both calli and roots. Analysis of these ten isozyme systems may facilitate identification of fusion products in Citrus.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 354-E, 1982 series     

Effect of red and far-red illuminations at the end of short days and their interaction with night-break illuminations, on flowering of Chrysanthemum morifolium plants

Flowering of chrysanthemum plants grown for 8 hr in sunlightwas delayed by 20 min of FR given prior to 16 hr dark periods.These FR illuminations increased the inhibition caused by thresholdamounts of night-break illuminations. On the other hand, 20min of R at the start of the dark period alleviated some ofthe inhibitory effects of the threshold of night-break illuminations. ¹Contribution from The Volcani Center, Agricultural ResearchOrganization, Bet Dagan, Israel, 1972 Series No. 2184 E. (Received August 26, 1972; )     

Somatic hybridization in Petunia

Summary Two types of cytoplasmic hybrids were obtained by protoplast fusion. These contained either one or the other original parental nucleus and heteroplasmon, a mix of plasmons inducing cytoplasmic male sterility and fertility. In subsequent generations, following selfing, stable male sterile and male fertile lines segregated from single fertile cytoplasmic hybrid plants. These data demonstrated the existence of a heteroplasmic state in the somatic hybrids and the occurrence of cytoplasmic segregation of the heteroplasmon into homoplasmons following the first and the second meiotic cycles.Contribution from the Agricultural Research Organization, The Volcani Center, Division of Plant Genetics & Breeding, Bet Dagan, Israel. No. 275-E, 1979 series     

Fertilization management of crops irrigated with saline water

Summary Available data concerning nutrition and fertilization effects on crops irrigated with saline water are presented and discussed. Published data on the salinity-fertility relationship are, at least to some extent, contradictory; both positive and negative effects as well as no effect of fertilization on salinity tolerance have been recorded. However, a great deal of the experimental work supports the view that standard fertilization recommendations for non-saline conditions are also suitable for saline conditions. In addition, available data indicate that the apparent salt tolerance of agricultural crops varies with soil fertility level. Consequently, crops showing exceptionally high apparent salt tolerance at a low fertility level become more sensitive when adequately fertilized, although the absolute yield may be greatly increased. On the other hand, some data seem to show a real increase in salinity tolerance under improved fertility conditions.Important information concerning the responses of plants to salinity under various fertility levels was obtained by tissue analysis. It should be kept in mind that this information may be influenced also by the plant species and by environmental conditions.Contribution from The Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1085-E, 1984 series.     

Parasites ofMonellia caryella [Hom.: Aphididae]: Phenology and effect on the aphid population in pecan orchards in Israel

One primary parasite,Trioxys pallidus (Haliday) (Hym.: Braconidae), and a secondary parasite,Aphidencyrtus sp., were identified from the blackmargined aphid,Monellia caryella (Fitch) (Hom.: Aphididae), in Israeli pecan orchards. The average total parasitism for all locations sampled was 13.5%. Although a hyperparasite was discovered, it had no significantly detrimental effect on the parasite. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No. 2034-E, 1987 series.     

Improved efficiency of plant regeneration from protoplasts of eggplant Solanum melongena L.

Eggplant (Solanum melongena L.) mesophyll protoplasts were obtained from in vitro growing plants of line 410 and cv. Classic. Relatively high (15%) plating efficiency was achieved using petri dishes with alternate quadrants containing reservoir medium (R medium + 1% activated charcoal) and culture medium. Shoot regeneration occurred within 6 weeks following initiation of protoplast culture.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan Israel, No. 1164-E, 1984 Series.     

Groundnut pod rot potential in three crop rotations,as indicated by the relative pythium population in soil

Summary The severity of a groundnut (Arachis hypogaea L.) pod rot caused byPythium spp. was found to depend on crop rotation. In order to evaluate Pythium in the soil, baits ofSorghum vulgare Pers. kernels soaked with Pimaricin were used. Most baited Oomycetes were identified asPythium spp. The relative population density of Oomycetes in the soil, one year before the final groundnut harvest, was indicative of pod rot incidence at that harvest. Part of work toward a Ph. D. thesis carried out at The Hebrew University of Jerusalem. Thanks are due to I. Wahl for his advice and criticism. Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel; 1971 Series, No.1862-E. Division of Plant Pathology.     

Occurrence of nitrite reductase in citrus leaves

Evidence is presented for the presence of nitrite reductasein citrus leaves. The enzyme has a Km for nitrite of 45 mu andis inhibited by cyanide. However, unlike citrus nitrate reductase(l), it is probably not a metalloflavo protein, although itmay be related to iron. In addition to the enzymatic nitrite reduction, non-enzymaticnitrite reduction was present in citrus leaf preparations. Underin vivo assay conditions nitrite reduction in one-month-oldleaves was not inhibited by cyanide, in contrast with three-month-oldleaves in which nitrite reduction was almost completely inhibited.Thus it appears that in very young citrus leaves most of thenitrite reduction is non-enzymatic. ¹ Contribution from The Volcani Center, Agricultural ResearchOrganization, P. O. B. 6, Bet Dagan, Israel. Series 1972.........2256AE. (Received November 28, 1972; )     

Differences in amino acid transport in isonuclear lines of cytoplasmic male-sterile and male-fertile petunia

Summary Two pairs of isonuclear lines of cytoplasmic male-sterile (CMS) and fertile (F) petunia cells grown in suspension culture in the presence or absence of amino acid sources were examined for uptake of 11 amino acids and adenosine. Cells from CMS lines exhibited a significant lower rate of uptake than F cells. These differences, for various amino acids, are a result of lower affinity (high Km) values and of lower maximal velocities. Although the uptake of most of the amino acids examined was affected by the availability of energy in the cell, the differences in uptake seem to be less dependent on the energy status of the cell.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 3351-E, 1991 series     

Root and microbial biomass dynamics under the canopy of the desert shrub Zygophyllum dumosum

Summary A study was done to evaluate the influence of soil moisture and rainfall on root and microbial biomass production under the canopy of the desert shrub Zygophyllum dumosum. During the study period the root biomass production increased following the early rains but subsequently declined, remaining fairly constant thoroughout the season. In contrast microbial biomass and soil organic matter increased during the rainy season and declined with the onset of the dry summer period. Based on our results we suggest that the moisture event and not the amount and the organic matter content regulate root and microbial biomass production at the 0 to 10 cm soil layer.Contribution of the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. paper no. 2617-E, 1989 series