增氧提高蔬菜磷素吸收利用的作用机制研究进展

磷素的吸收利用率低是制约蔬菜生产的重要障碍因子之一,蔬菜根系形态和生理特性的适应性变化是高效利用土壤磷的主要生物学机制。当前磷肥的过量施用导致蔬菜根际环境的恶化,而根际环境对蔬菜的根系形态结构、根系活力和植株生理反应也都会产生反馈影响。本文从氧营养的角度,以根系为核心,综述了国内外提高蔬菜磷素利用率的途径,根系与根际环境互作对蔬菜磷素利用率的响应,并剖析了增氧促进根系生长及改善根际环境提高蔬菜对磷的吸收及利用的生物学机制,从而为提高蔬菜磷肥利用效率、减少蔬菜地磷肥投入量提供理论依据。     

Effects of Green Manures and Zinc Fertilizer Sources on DTPA-Extractable Zinc in Soil and Zinc Content in Basmati Rice Plants at Different Growth Stages

Rice is very sensitive to low zinc(Zn) supply in submerged paddy soils and Zn deficiency is one of the major limiting factors in determining rice production in India. A field experiment was conducted during the summer-rainy seasons of 2009 and 2010 at the research farm of the Indian Agricultural Research Institute, New Delhi, to determine the effects of summer green manure crops and Zn fertilizers on diethylenetriaminepentaacetic acid(DTPA)-extractable(available) Zn concentration in soil and total Zn content in Basmati rice cultivar Pusa Basmati 1 at periodic intervals. Summer green manure crops included Sesbania aculeata(Dhaincha),Crotalaria juncea(Sunhemp), and Vigna unguiculata(Cowpea) and the Zn fertilizers used were ethylenediaminetetraacetic acid(EDTA)-chelated Zn, ZnSO_4·7H_2O, ZnSO_4·H_2O, ZnO, and ZnSO_4·7H_2O + ZnO. Beneficial effects of summer green manure crops and Zn fertilizers on DTPA-extractable Zn concentration in soil and total Zn content in dry matter of Basmati rice at periodic intervals were observed, with significant increases in all the determined parameters, in comparison with those in the control(no Zn application or summer fallow). The rate of increase varied among summer green manure crops and Zn fertilizers during both years. Among the summer green manures, incorporation of S. aculeata led to a significant increase in mean Zn content in Basmati rice grain and straw when compared with C. juncea, V. unguiculata, and summer fallow treatments. Among the Zn fertilizers, significant increases in Zn content in Basmati rice dry matter and DTPA-extractable Zn concentration in soil during various growth stages of the plant were recorded with EDTA-chelated Zn application, followed by the application of ZnSO_4·7H_2O, ZnSO_4·H_2O, ZnSO_4·7H_2O + ZnO, ZnO,and no Zn. The highest mean Zn content in Basmati rice grain and straw was recorded with EDTA-chelated Zn application in 2009 and 2010, respectively. The application of ZnSO_4·7H_2O was the second best treatment after EDTA-chelated Zn; however, it was statistically inferior to EDTA-chelated Zn. The lowest values were recorded with the control(no Zn application) during both years of study. The amount of Zn concentration in soil was found to be significantly positively correlated with the Zn content in Basmati rice dry matter during both years. Significantly higher levels of residual fertility in soil after the harvest of Basmati rice were observed with application of EDTA-chelated Zn and incorporation of S. aculeata when compared with those of other Zn sources and summer green manures.     

缺钾对茶树幼苗叶片叶绿素荧光特性的影响

为了探明缺钾对茶树叶片的光合电子传递、光能转化和利用等的影响机制,本研究以10月龄扦插瑞香茶[Camellia sinensis (L.) O. Kuntze cv. Ruixiang] 苗为试验材料,通过沙培试验,用含5个不同钾浓度（K 0、100、200、600、2000 mol/L）的营养液浇灌,每周3次,处理24周后,进行茶树叶片叶绿素荧光参数的测定。结果表明,缺钾处理茶树叶片OJIP曲线O点上升,P点下降,同时出现150 s处的L点和300 s处的K点两个新点;缺钾条件下,TRo/ABS (or Fv/Fm) (最大光化学效率)、ETo/ABS（电子传递的量子产额）、REo/ABS（还原量子效率）、PIabs（吸收光能的性能指数）和PICS（单位面积为基础的性能指数）下降,而VJ、VI和耗散能增加。总之,缺钾损伤了从PSⅡ供体侧到PSI的整个电子传递链,降低了光合电子传递能力;缺钾叶片还通过增加热耗散以保护叶片在强光下免遭光氧化伤害。     

Optimization of DTPA and calcium chloride extractants for assessing extractable metal fraction in polluted soils

Abstract

Metal availability in soils is often assessed by means of extraction with chemical solutions, among others the chelating agent DTPA (diethylenetriaminepentaacetic acid) and the non‐buffered salt calcium chloride (CaCl₂). The same procedures are used for polluted soils that were originally created to assess the nutrient status of arable soils. We studied the influence of various parameters (type of shaker, shaking time, soil to solution ratio, and concentration of chemical extractant) and modify the DTPA and CaCl₂ extraction procedures to make them suitable for the study of polluted soils. The chosen extraction ratio and extractant concentration were the followings: 8 g/20 mL of 0.1 MCaCl₂ and 2 g/20 mL of 0.005 M DTPA. The optimized procedures were applied to nine soil samples affected by different sources of pollution (mine works, vehicle emissions, and various industries). Cadmium (Cd) showed the highest extractability with both extractants. Depending on the soil, copper (Cu) and zinc (Zn) (using DPTA) and Cu and manganese (Mn) (using CaCl₂) were the followings in the extractable amounts. Cadmium, Cu, and Zn were highly correlated in both extractions and with total contents.     

Genotypic Differences in Spectral and Photosynthetic Response of Peanut to Iron Deficiency

To assess the genetic variability of peanut (Arachis hypogaea L.) in tolerance to iron (Fe) deficiency, spectral and photosynthetic parameters of 12 peanut cultivars were determined. The results showed that peanut exhibit significant variations in spectral and photosynthetic parameters within cultivars in response to Fe deficiency. The 12 peanut cultivars were separated into three groups, which include (i) a Fe-deficient tolerant cultivar (‘Zhenghong 3’), (ii) a Fe-deficient sensitive cultivar (‘Huayu 22’), and (iii) ten intermediate cultivars. Iron deficiency caused an increase in root biomass, root/shoot ratio, structure independent pigment index and intercellular carbon dioxide (CO₂) concentration, but resulted in a decrease in net photosynthetic rate (Pn), quantum yield of PS II photochemistry (F_v/F_m), effective quantum yield of PS II (ΦPS II), photochemical reflectance index, red edge point, and chlorophyll normalized difference index. Iron deficiency-induced decline in net photosynthetic rate may be resulted from the reduction of photosynthetic pigment contents and inhibition of PSII photochemistry.     

Diagnosis of Sulfur Status of Winged Bean [Psophocarpus Tetragonolobus (L.) Dc] by Plant Tissue Analysis

Winged bean [Psophocarpus tetragonolobus (L.) DC] plants, line UPS31, were grown in pots of sulfur (S)-deficient soil in a glasshouse without added S or with five levels of added S. The seed was inoculated with rhizobia (Bradyrhizobia sp. strain CB756) and plants were later given additional mineral nitrogen (N). Harvests of shoots were made at 39 and 78 days after sowing (DAS). Shoot dry matter yield, total S (S_T), S reducible by hydriodic acid (S_HI) – a measure of sulfate – and N were determined. At 78 DAS, the critical concentration (at 90% maximum yield) of S_T in shoots was 0.9 mg S g^?1 dry matter and in young leaves was 1.4 mg S g^?1 dry matter. Plants with these concentrations or below would be considered S-deficient. The usefulness of critical concentrations of S_HI or ratios of S_HI/S_T, and N/S_T as indicators of S status is discussed.     

Growth and Nutritional Disorders of Eggplant Cultivated in Nutrients Solutions with Suppressed Macronutrients

The objective was to evaluate the effects of omitting macronutrients in the nutrients solution on growth characteristics and nutritional status of eggplants. The treatments were complete nutrients solution and solutions with nutrient omission: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). The experiment was carried out under greenhouse conditions with three replicates in a completely random design. Plant height, number of leaves per plant, leaf area, relative chlorophyll index, photosynthesis rate, stomatal conductance, dry matter, concentration levels of macronutrients in plant aerial part and root system, and nutritional disorders were evaluated. Omitting elements interfered in the concentration of elements in the various plant tissues and this had as consequences limited vegetative growth, reduced dry matter and led to the development of the typical deficiency symptoms of each element. Although potassium was the most demanded of all elements, nitrogen and calcium were the most growth limiting ones.     

Nodulation and nitrogen fixation of Lupinus species with Bradyrhizobium (lupin) strains in iron-deficient soil

 The effect of six Bradyrhizobium sp. (lupin) strains (WPBS 3201D, WPBS 3211D, USDA 3040, USDA 3041, USDA 3042 and CB 2272) and Fe supply on nodulation, N₂-fixation and growth of three lupin species (Lupinus termis, L. albus and L. triticale) grown under Fe deficiency in an alkaline soil, were examined in sterilized and non-sterilized pot experiments. When inoculated with USDA 3040, 3041, 3042 and CB2272 without Fe addition, the three lupin species had a very low nodule number and mass, low shoot and root dry matter accumulation and lower N yield. However, inoculation with WPBS 3201D and 3211D without Fe treatments increased all these parameters substantially. The ability of WPBS 3201D and 3211D to form nodules on the three lupin species under conditions of Fe stress could be attributed to their ability to scavenge Fe from Fe-deficient environments through their siderophore production. Addition of Fe to the other four strains significantly increased nodulation and N₂-fixation of the three lupin species, indicating that the poorer nodulation and N₂-fixation of these strains in the absence of Fe, resulted from a low ability to obtain Fe from alkaline soils. Bradyrhizobium strains WPBS 3201D and 3211D were superior to the other four strains in terms of promoting greater nodulation, N₂-fixation, plant growth and N accumulation of L. termis and L. albus. However, the other four strains were more efficient in symbiotic association with L. triticale. The greater variations in nodule efficiencies (specific nitrogenase activity) under different levels of Fe supply could be attributed to the quantities of bacteroid protein and leghaemoglobin in the nodules. The results suggested that Bradyrhizobium (lupin) strains differ greatly in their ability to obtain Fe from alkaline soils, and that the selection of bradyrhizobial strains which are tolerant of Fe deficient soils could complement plant breeding for the selection of legume crops for Fe-deficient soils. Received: 5 January 1998     

磷素对高硼土壤小麦生长的影响

为减轻高硼(B)对小麦的毒害作用,研究了不同土壤B浓度下磷(P)素对小麦生长的影响。结果表明,增施P素能减轻小麦B毒害症状,小麦平均黄叶率由9.95%降至7.60%;促进小麦生长,B浓度为50mg/kg时,小麦根系和地上部分生物量分别增加44.9%和11.72%,30cm以下土层根系平均增加2.1%,促进了小麦对深层养分和水分的利用。     

磷酸一钙施用模式对水稻有效性及土壤中有效磷分布的影响

利用温室盆栽试验研究了磷酸一钙不同施用模式对水稻的有效性及土壤中有效磷(P)分布的影响,并提出了水田中P肥的施用模式。结果表明:P肥撒施时,表层水中总P浓度最高,达4.8mg/L,而其他施肥模式下表层水中总P浓度可满足GB3838-2002Ⅲ类水水质要求;混施可为水稻提供立体的吸收空间,有效性高;沟施时,肥料P主要集中在施肥带上下约3cm的范围内;在水田中,施用P肥时应优先考虑混施,若土壤中P素有效性相对较高,应尽量在旱作时施用。