Secretion of Phy tosiderophore and Its Effects on Soil Fe Availability

Large amounts of phytosiderophore are detected from both the solution and the rhizosphere soil when cereal crops are under Fe deficiency stress. The extension of phytosiderophore in the rhizosphere soil is found only within 1 mm apart from the root surface. The rate of phytosiderophore secretion is negatively related to chlorophyll content in young leaves and positively related to the Fe-solubilizing capacity. Results from in vitro experiments show 10 μmoles mugineic acid can dissolve 501 μg Fe from iron hydroxide and 146 ug from strengite. Thus, phytosiderophore can considerably enhance the soil iron availability by increasing the solubility of amorphous iron hydroxide and iron phosphate, and active Fe is consequently accumulated in the plant rhizosphere , 43% higher than in the bulk soils. There is evidence to support that mugineic acid chelates with Fe3+at a rate of 1:1 in the acid condition. In addition ,we observe mugineic acid has certain effects on mobilization of P as well as Fe by dissolving the insoluble iron phosphate. And phytosiderophore seems to be an effective remedy for the chlorosis of dicotyledonous plants.

Effects of temperature,algae biomass and ambient nutrient on the absorption of dissolved nitrogen and phosphate by Rhodophyte Gracilaria asiatica

Gracilaria asiatica, being highly efficient in nutrient absorption, is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate. It was cultured in a laboratory simulating field conditions, and its nutrient absorption was measured to evaluate effects of environmental conditions. Ammonia nitrogen （AN）, nitrate nitrogen （NN）, total inorganic nitrogen （TIN）, and soluble reactive phosphorus （SRP） uptake rate and removal efficiency were determined in a 4~2 factorial design experiment in water temperatures （T） at 15~C and 25~C, algae biomass （AB） at 0.5 g/L and 1.0 g/L, total inorganic nitrogen （TIN） at 30 ~tmol/L and 60 ~tmol/L, and soluble reactive phosphorus （SRP） at 3 and 6 ~tmol/L. AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN, NN, TIN, and SRP （P〈0.001）. G. asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L. Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations; nutrient removal efficiency decreased at higher environmental nutrient concentrations. The algae preferred to absorb AN to NN. Uptake rates of AN, NN, and SRP were significantly affected by temperature （P〈0.001）; uptake rate was higher for the 25~C group than for the 15~C group at the initial experiment stage. Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups （P〈0.01）. The four factors had significant interactive effects on absorption of N and P, implying that G. asiatica has great bioremedial potential in sea cucumber culture ponds.

Relationship between Ponkan Mandarin Fruit Quality and Nutrient Concentrations

Five age groups of trees were carried out in order to study relationships between the deterioration of Ponkan mandarin fruit quality and changes in tissues nutrient concentrations with tree age.Fruit quality and nutrient concentrations in fruits and leaves were measured.Comprehensive fruit quality decreased in the order:5-year-old > 13-year-old > 38-year-old > 8-year-old >18-year-old.In 18-year-old trees,calcium(Ca) concentrations of fruit and leaf were lower,while potassium(K) and boron(B) concentrations of fruit and magnesium(Mg) and manganese(Mn) concentrations of leaf were higher.Negative relationships were observed between fruit total soluble solids and leaf B,while positive relationships were observed between fruit total soluble solids and leaf and fruit Ca concentrations,and between titratable acidity and leaf Mn.Fruit quality decreasing with tree age most likely resulted from an imbalance of high K,Mg and B but lower Ca concentrations in leaves and fruits.

湖南城步县不同村组间虫茶若干品质特征的差异性分析

为了解决如何鉴别虫茶的优劣品质问题,通过收集不同村组和不同农户的虫茶,进行化学和物理性能的检测,并应用SPSS软件进行方差、回归、卡平方等统计方法,对湖南省城步县几个不同村组或不同农户生产的虫茶的某些品质特征(原料含水量、虫茶浸出液的可溶物浓度、浊度和pH值)进行了比较分析,结果表明,对于原料含水量,在不同村组或不同农户间存在显著差异;而对于虫茶浸出液的可溶物浓度、浊度和pH值,则不仅在不同生产者之间存在一定的差异,而且还会因虫茶原料含水量不同和泡茶时的用水量不同而不同。该结果可为虫茶品质优劣鉴定标准的制定提供参考依据。