Phylogenetic and expression analysis of the magnesium transporter family in pear,and functional verification of PbrMGT7 in pear pollen

The magnesium ion (Mg²⁺) is the most abundant divalent cation in living cells, and it plays essential roles in various cellular functions. Mg²⁺ homeostasis in plant cells is crucial for plant growth. The MRS2/MGT family of proteins localise to various membranes, and they function during Mg²⁺ transport in plants, but their functions are largely unknown in fruit trees. In this study, we performed a genome-wide analysis to identify the MGT gene family members in the pear Pyrus bretschneideri. Sixteen MGT genes were identified. Analysis of the activity of pear pollen showed that a low-concentration magnesium ion treatment was beneficial for pollen germination and pollen tube growth. None of the 16 MGT genes were expressed in any unique tissue, including pollen, and their expression in magnesium-treated pollen varied greatly, where PbrMGT7 was the most sensitive and it was tested as a representative. PbrMGT7 could functionally complement a bacterial strain deficient in Mg²⁺, thereby indicating a role in magnesium transport. A co-localisation experiment confirmed that PbrMGT7 was localised in the mitochondria, which suggests that PbrMGT7 could mediate Mg-trafficking between the mitochondria and cytosol. Overall, these results suggest that PbrMGT7 is related to Mg²⁺ homeostasis during pear pollen tube growth.??     

山东省土壤交换性镁含量及分布

通过对全省不同土壤类型１１０５个耕层土壤样本的调查分析,明确了全省土壤交换性镁含量平均为０．４８ｇ／ｋｇ土,最低０．０２ｇ／ｋｇ土,最高２．４１ｇ／ｋｇ土,不同土类交换性镁含量高低依次为潮土＞盐土＞砂姜黑土＞褐土＞粗骨土＞棕壤。分析了不同地貌类型区土壤交换性镁含量及分布规律,为全省不同地区重视和合理应用镁肥提供了依据。     

一些牧草的耐酸性及磷,钾,镁肥对牧草的影响

试验研究了 ６ 种多年生牧草的耐酸性及酸性土壤磷、钾、镁肥对牧草的影响⒚结果显示：耐酸性为羊茅草、毛花雀稗＞ 白三叶草、多年生黑麦草＞ 草地羊茅、红三叶草⒚耐酸牧草在不同 ｐ Ｈ 条件下植株的含铝量、含磷量差异不大;耐酸性弱的牧草 在低 ｐ Ｈ 条件下,植株含铝 量显著较高⒚缺磷、缺 钾和缺镁处理的产量分别 为完全肥料处理 的 １１％ ～１７％ ,８７％ ～９３％ ,７７％ ～９０％ ,显 示这些土壤中缺 磷是限制牧草产量的主要营养元素⒚缺磷处理植株磷、钾含量显著较低,氮含量显著较高⒚     

Differences in Major Ions Composition of Artificial Seawater from Aquarium Tanks at the New Jersey State Aquarium

Concentrations of major seawater ions were monitored in six aquarium tanks at the New Jersey State Aquarium over a three-year period. The ratios of these ions to chlorinity were compared to those in freshly prepared artificial seawater. The largest aquarium tank (Ocean Tank) exhibits statistically significant (p<0.01) relative enrichment of potassium, calcium and strontium, and relative depletion of magnesium and sulphate. The likely source of excess potassium is from potassium iodide added to prevent goiter in sharks. Based on the excess potassium, a total amount of 650 μmol/kg iodide added over the years was calculated for the Ocean Tank. The excess calcium observed in several tanks correlates with the presence of concrete or arbonaceous shells in these tanks. In Ocean Tank, a calcium leaching rate of 6.7 kg/month was calculated. Continuous formation of white carbonaceous precipitates serves as a sink for magnesium in Ocean Tank, and a magnesium removal rate of 5.1 kg/month was calculated. These and other results show that concentrations of major ions in artificial seawater aquaria are affected by leaching, precipitation and addition of food supplements, and these factors should be taken into account when preparing artificial seawater for aquarium tanks with long water residence time. This revised version was published online in August 2006 with corrections to the Cover Date.     

氢氧化镁对水质、底质改良的研究与应用

近年,沿海各地区水产养殖业发展迅速。由于内湾海区海水循环交换能力较弱,黑臭底泥的长期堆积,导致养殖水体水质和底质进一步恶化,然而这种问题普遍存在于封闭式或半封闭式水域环境中。对此,氢氧化镁作为水质、底质改良剂被应用于水环境的治理。本文概述了氢氧化镁的作用机理,包括氢氧化镁与悬浮颗粒物的静电、对氮磷的降解及对硫化氢的降解等作用;同时介绍了氢氧化镁在海水养殖场、淡水湖泊和水库、水华防控、赤潮防控及废水处理中的研究与应用;展望了氢氧化镁和纳米级氢氧化镁在水体环境领域的应用前景。     

Delay of the egg activation process in the Black Tiger Shrimp Penaeus monodon by manipulation of magnesium levels in spawning water

The aim of this study was to determine whether magnesium (Mg²⁺) in seawater is required for egg activation of the black tiger shrimp Penaeus monodon and whether manipulation of Mg²⁺ levels can be used to delay the process and thereby synchronize egg activation. Female P. monodon broodstock were allowed to spawn in artificial seawater containing Mg²⁺ at varying levels with respect to the normal (100%) level: 100%, 50%, 20% and 0%. Egg activation occurred normally at 100% Mg²⁺, incompletely at 50% and 20% Mg²⁺ levels and did not occur at all with 0% Mg²⁺. The fertilization rate with 100% Mg²⁺ was observed to be 83%, but fertilization failed to take place in all the other groups. The fertilization rate was restored from 0% to 76% following the 20% Mg²⁺ level treatment when Mg²⁺ levels returned to normal (100%) as soon as spawning was completed. This study suggests that the level of Mg²⁺ in seawater plays a vital role in P. monodon egg activation, and that commencement of this process could be delayed by manipulation of the Mg²⁺ level during and immediately after spawning.     

Nitrogen,phosphorus, potassium and magnesium contents of field vegetables — Recent data for fertiliser recommendations and nutrient balances

When calculating fertiliser recommendations and nutrient balances, growers and advisers usually do not do site specific measurements but use data from look up tables. Data given by older literature sources, however, do not take into account today's cropping practices. Therefore a databank on nutrient contents of total yields, marketable yields and harvest residues of 22 field vegetable crops is presented. This databank was compiled using results from topical field experiments and from recent literature.     

添加氧化镁和铵明矾对菜田高磷土壤活性磷的影响

为研究不同种类钝化剂对土壤磷素的固定效果,通过室内培养试验,向土壤中添加氧化镁、铵明矾及二者不同比例的混合物,研究其对土壤0.01 mol·L~(-1)CaCl_2浸提磷、0.5 mol·L~(-1)NaHCO_3浸提磷含量及磷素组分的影响。结果表明:与未钝化的对照处理相比,向土壤分别添加0.5%和2.0%(m/m)的氧化镁、铵明矾或其混合物培养45 d后,均显著降低了土壤CaCl_2浸提磷含量。添加氧化镁或铵明矾分别降低了87.8%(0.5%)、98.0%(2.0%)和44.4%(0.5%)、88.8%(2.0%)的CaCl_2浸提磷含量,而二者混合物的钝化效果明显弱于氧化镁。添加2.0%的氧化镁、铵明矾或其混合物对土壤NaHCO_3浸提磷含量降低明显,但氧化镁和铵明矾的混合物降低土壤NaHCO_3浸提磷的效果弱于铵明矾。对培养45 d后的土壤进行Hedley分组测定磷素组分发现,添加氧化镁或铵明矾显著降低了土壤H_2O浸提总磷和NaHCO_3浸提总磷含量,添加铵明矾显著增加了土壤中Na OH浸提总磷的含量。氧化镁、铵明矾和土壤活性磷不同的作用机理是导致氧化镁固定CaCl_2-P效果显著而铵明矾固定Olsen-P效果显著的主要原因。     

镁素处理对艾纳香药材生物量和营养元素积累的影响

以一年生艾纳香种子苗为实验材料,用七水合硫酸镁提供镁素,测定生长期艾纳香生长指标和生物量,采用 凯氏定氮仪测定艾纳香药材氮含量,采用钼锑抗比色法测定磷含量,以及采用原子吸收光谱法测定艾纳香药材钾、钙、 镁、铁、锰、铜和锌含量,以研究镁素对艾纳香药材生物量和营养元素积累的影响。结果表明：镁素显著增加了艾纳 香叶长、叶宽、株高和地径等生长指标,显著增加了艾纳香药材叶片、茎和叶茎总生物量,对叶茎生物量比影响不显 著;镁素对艾纳香叶片中氮含量影响不显著,钙和铁含量显著降低,1.5 mg/mL 镁素处理组磷、钾和镁含量显著高于其 他处理组,15 mg/mL 镁素处理组锰、锌和铜含量最低,显著低于其他处理组。在艾纳香生长期施加镁素可以促进艾纳 香生长,提高药材生物量,显著促进磷、钾和镁积累,抑制钙和铁的吸收,对氮影响不显著,15 mg/mL 镁素处理组锰、 锌和铜含量最低。