Specific ion effect on the accumulation of abscisic acid in wheat

Studies were carried out in the glass house using sand culture to find out the specific ion effect on the accumulation of abscisic acid in wheat. Seeds were sown in sixteen different solutions of chloride, sulphate, nitrate, carbonate salts of sodium, potassium, calcium and magnesium used each at ‐2 bar osmotic potential. The leaf samples taken after 25 days of sowing indicated that osmotic as well as salt stress increased significantly the accumulation of abscisic acid. The accumulation of abscisic acid was significantly less under potassium and calcium salt ions as compared to that under sodium and magnesium salts ions. Overall effect of anions showed that accumulation of abscisic acid was more under PEG (osmotic stress and chloride salts but it was less under sulphate and nitrate salts and was the least under carbonate salts. The accumulation of abscisic acid was exceptionally high under potassium dihydrogen phosphate. In general, the accumulation of abscisic acid‐a growth inhibitor varied not only with the type of the cation but also depended on the accompanying anion indicating differential growth response of plants under different types of saline conditions having dominance of different salt ion(s).     

Influences of ultra‐violet (UV)‐blue light radiation on the growth of cotton. I. Effect on iron nutrition and iron stress response

Cool white fluorescent (CWF) light reduces Fe³⁺ to Fe²⁺ while low pressure sodium (LPS) light does not. Cotton plants grown under CWF light are green, while those yrown under LPS light develop a chlorosis very similar to the chlorosis that develops when the plants are deficient in iron (Fe). It could be that CWF light (which has ultra violet) makes iron more available for plant use by maintaining more Fe²⁺ in the plant. Two of the factors commonly induced by Fe‐stress in dicotyledonous plants‐‐hydroyen ions and reductants released by the roots‐‐were measured as indicators of the Fe‐deficiency stress response mechanism in M8 cotton.

The plants were grown under LPS and CWF light in nutrient solutions containing either NO₃‐N or NH₄‐N as the source of nitrogen, and also in a fertilized alkaline soil. Leaf chlorophyll concentration varied significantly in plants grown under the two light sources as follows: CWF+Fe > LPS+Fe > CWF‐Fe ≥ LPS‐Fe. The leaf nitrate and root Fe concentrations were significantly greater and leaf Fe was generally lower in plants grown under LPS than CWF light. Hydrogen ions were extruded by Fe‐deficiency stressed roots grown under either LPS or CWF light, but “reductants”; were extruded only by the plants grown under CWF light. In tests demonstrating the ability of light to reduce Fe³⁺ to Fe²⁺ in solutions, enough ultra violet penetrated the chlorotic leaf of LPS yrown plants to reduce some Fe³⁺ in a beaker below, but no reduction was evident through a yreen CWF grown leaf.

The chlorosis that developed in these cotton plants appeared to be induced by a response to the source of liyht and not by the fertilizer added. It seems possible that ultra violet liyht could affect the reduction of Fe³⁺ to Fe²⁺ in leaves and thus control the availability of this iron to biological systems requiring iron in the plant.     

Nitrogen-Metabolizing Enzymes: Effect of Nitrogen Sources and Saline Irrigation

Abstract

Indian mustard (Brassica juncea L. cv. RH-30) was grown under different types and levels of nitrogen (N) sources, i.e. nitrate, ammonical, and nitrate plus ammonical, at 40, 80, and 120 kg ha^{? 1} under green house conditions. The plants were salinized with 8 and 12 dSm^{? 1} at 35 and 55 days after sowing. A progressive inhibition of the activity of enzymes of N metabolism, i.e., nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH), was observed with increasing level of salinity. However, the magnitude of such reductions was lowest at the highest level of N (120 kg ha^{? 1}) as compared with the lowest level (40 kg ha^{? 1}) irrespective of N source. The activity of nitrate-assimilating enzymes (NR and NiR) was maximum with nitrate fertilizer, and minimum with the ammonical form. The alleviation of detrimental effects of salinity on NR and NiR was better with the highest level of N (120 kg ha^{? 1}) in nitrate form as compared with the lowest level of N (40 kg ha^{? 1}). In contrast, the maximum activity of ammonium-assimilating enzymes (GS, GOGAT, and GDH) was observed with the highest level of N (120 kg ha^{? 1}) and the minimum with the nitrate form of N under salinity. These results indicate that despite the high salinity, an increase in the concentration and uptake of N stimulates the activities of nitrate-assimilating enzymes (NR and NiR) as well as of the ammonia-assimilating enzymes (GS, GOGAT, and GDH).     

Feldskalige variabilität von frühjahrsfeuchte und mineralischem stickstoff in der ungesättigten zone sandiger standorte Nordostdeutschlands

Auf sandigen Standorten des Jungpleistozäns wurden die Variabilität der Frühjahrsfeuchte und des mineralischen Stickstoffgehaltes im Porenwasser unter verschiedenen Landnutzungsbedingungen bis 4,2 m Tiefe analysiert. Das Mittel der Frühjahrsfeuchte lag bei etwa 10 cm³/100 cm³. Die hohe standörtliche Variabilität der Frühjahrsfeuchte (Variationskoeffizienten von 26-63%) beruhte weitgehend auf Substratheterogenitäten der Geogenese. Endmoränen hatten die höchste Gesamtvarianz, Flugsanddecken zeigten die höchste Strukturvarianz. Die untersuchte Sanderfläche wies eine geringere Feuchteheterogenität auf als die Grundmoränenflächen. Bei Beprobungsabständen von 10 m wurden Reichweiten der Autokorrelation im Dekameterbereich gefunden. Die Standorte mit Flugsanden und die Sanderfläche wiesen relativ große Reichweiten der Autokorrelation auf (Reichweite 140 m), die Endmoränenstandorte und die endmoränennahe Grundmoräne waren besonders kleinflächig strukturiert (Reichweite 20-40 m). Die Gehalte an mineralischem Stickstoff in der ungesättigten Zone widerspiegelten die Landnutzung und wiesen noch höhere Variabilität auf als die Frühjahrsfeuchte. Unter ehemaliger Güllebewirtschaftung wurden sehr hohe Mengen mineralischen Stickstoffs ermittelt. Hohe N-min -Konzentrationen wurden auch unter einem Kiefernforst gemessen. Extensiv genutztes Grasland wies die geringsten Mengen und Konzentrationen an mineralischem Stickstoff auf. On sandy Pleistocene sites the variability of springtime soil moisture content (field capacity) and mineral nitrogen in pore water were analysed down to 4.2 m depth under different land use systems. The average of the field capacity was about 10 cm³/100 cm³. Their large site-specific variability (variation coefficients of 26-63%) is mainly due to the substrate heterogeneity of the pedogenesis. End moraines had the highest total variability, aeolic sand layers were strongly spatially dependent. The sandy outwash area had the lowest variability of field capacity, lower than the glacial tills. Considering sampling distances of 10 m, the autocorrelation length was also in the range of decametres. Areas of aeolic sands and outwash sands showed relatively large ranges of autocorrelation (140 m), end morains and glacial tills neighboured to end moraines are structured into smaller areas (range of autocorrelation 20-40 m). The amounts of mineral nitrogen in the vadose zone reflect the land use and show larger variability than the field capacities. Highest amounts were found in arable land of former intensive slurry application. High nitrogen concentration were also measured under a pine forest. Not fertilized grassland had the lowest amounts and concentrations of mineral nitrogen.     

氮肥用量对旱地冬小麦产量及夏闲期土壤硝态氮变化的影响

在陕西渭北旱塬,利用长期定位试验研究了长期不同氮肥用量（0、80、160、240、320 kg hm-2）对旱地冬小麦产量形成,氮素利用,土壤硝态氮残留、夏闲期淋溶和矿化的影响。结果表明：随用量增加,施氮提高旱地小麦产量的效应下降,而土壤硝态氮残留迅速增加。作物生长当季的硝态氮残留主要分布在0～60 cm土层,施氮超过160 kg hm-2时,达56.8～211.7 kg hm-2,来源于当季施用氮肥的残留占64%～90%。夏闲期土壤硝态氮发生淋失的土层深度和硝态氮淋失量均与施氮量呈显著的抛物线关系（r = 0.988 9和0.994 0）,施氮量超过160 kg hm-2时,每增加100 kg hm-2的氮肥投入,硝态氮淋失深度和淋失量增加量分别高于27 cm和80.4 kg hm-2。平均每10 mm的夏闲期降水可使离开原土层发生淋溶的硝态氮向下移动2～4 mm。施氮量对硝态氮淋失的深度没有显著影响。夏闲期土壤氮素矿化量、来源于当季施入土壤肥料氮被生物固定后的再矿化量分别为51.8～160.9 kg hm-2和31.6～109.2 kg hm-2。基于本研究,建议渭北旱塬冬小麦施氮量控制在146～163 kg hm-2,以保证旱地小麦高产,防止过量肥料氮残留,减少淋溶风险。     

茶树花青素还原酶的酶学特性研究

茶树花青素还原酶(CsANR)作为原花青素生物合成途径中的关键酶,催化花青素为相应的2,3-顺式-黄烷-3-醇。为了研究该酶的酶学特性,本文采用原核表达及钴离子亲和柱纯化技术,表达并纯化出目的蛋白;重点对CsANR1酶学特性进行研究分析。结果表明,CsANR1的最适反应温度为40℃,最适pH值为6.5;对底物矢车菊色素的亲和力高于飞燕草色素。Cu2+、Co2+、Fe2+、Mn2+、Zn2+和Hg2+等金属离子对酶有抑制作用,存放15d后酶活下降50%。     

Genetic Variations in Dry Matter Production,Nitrogen Uptake,and Nitrogen Use Efficiency in the AA Genome Oryza Species Grown under Different Nitrogen Conditions

Abstract

To clarify the genotypic variation of nitrogen (N) response in the AA genome Oryza species, we investigated dry matter production, N uptake, N and water use efficiencies (NUE and WUE), bleeding sap rate (BR), and root morphological traits at vegetative stage in 6 cultivars and 4 strains of 6 species (O. sativa, O. glaberrima, O. barthii, O. nivara, O. meridionalis, and O. rufipogon) grown under standard N (SN) and low N (LN) conditions. Some wild Oryza strains and O. glaberrima showed high dry matter production under both N conditions. In most plants, total dry weight decreased and root dry weight increased under the LN condition, resulting in decreased top-root ratio. In japonica cultivars of O. sativa, however, these traits were unaffected by the N condition. There were no significant differences in WUE with plant species or N conditions. In all plants, however, NUE was higher in the LN than SN condition, and was conspicuously high in most wild Oryza species and O. glaberrima. Some of them showed increased capacity of nitrate-N (NO₃-N) uptake under the LN condition. In cultivars and strains with a high NUE, root dry weight, root surface area, and BR were also higher under the LN condition. These results suggest that a high NUE is associated with the development of a root system, increased BR, and probably increased capacity of NO₃-N uptake. This study revealed the presence of superior wild Oryza strains for growth under LN that may be a promising genetic resource for low N-input agriculture.     

Nitrate-Induced Inhibition of Root Nodule Formation and Nitrogenase Activity in the Peanut (Arachis hypogaea L.)

Summary

The effect of nitrate in the culture solution (0.7, 3.5, 7.0, and 14.0 mM N) on the growth, root nodule formation and nitrogenase activity of the peanut (cv. chico) inoculated with Bradyrhizobium sp. was examined at early developmental stages. The amount of nitrogen derived from fixation and its percentage to total nitrogen in the nitrate-fed plant were evaluated using ¹⁵N labeled nitrate. The dry weight and total nitrogen content of the plant at 40 days after transplanting (day 40) varied with the concentration of nitrate in the culture solution. Both of them were higher in the plants grown in the presence of nitrate at the concentrations above 0.7 mM. On the other hand, the number and fresh weight of nodules, and acetylene reduction activity per plant were the lowest in the presence of nitrate at 14.0 mM, relatively high at 0.7 mM, and the highest at 3.5 mM. The proportion of N derived from atmosphere to total nitrogen in the plants examined at days 18 and 33 was 23–31% in the presence of nitrate at 3.5 and 14.0 mM. However, the proportion examined at day 48 was as high as 57–58% at 3.5 mM, and it was only 22–24% at 14.0 mM.     

Non‐selective grazing as a means of veld reclamation

Ecology embraces the study of the structure and function of eco‐systems. Seven fields of ecology may be distinguished viz. systems, production, phytosociological and physiological ecology, and aut‐, gen‐ and paleoecology. A review is given of the objects and main investigational facets of each. The future of ecology is discussed in a conjectural way. A new surge of awareness of the need for conservation has become manifest. There have been recommendations that large species pools be preserved, against a snowballing population pressure, in conserved natural areas representing different ecosystems. The impoverishment of species diversity, and denudation of the earth surface cannot be contemplated with equanimity. The time spent on ecological research of a theoretical and sophisticated nature should bear some relationship to the degree of development of a country.     

The effect of form and level of nitrogen fertlization on the yield of Digitaria eriantha Steud*

Abstract

On dryland Digitaria eriantha ammonium sulphate and limestone ammonium nitrate were superior to potassium nitrate and urea. With reference to the level of nitrogen fertilization it was found that levels in excess of 300 kg N/ha, and up to 400 kg N/ha, could be economically justified, even on a pasture with a high basal level of fertility.