外源硅添加对草地早熟禾硅素吸收及根系生长的影响

采用溶液培养法,以草地早熟禾(Poa pratensis L.)品种‘午夜'为试验材料,研究了不同硅素水平对草地早熟禾硅素吸收、叶片相对电导率、根冠比和根系生长发育的影响。结果表明:随着硅素浓度的增加,硅素吸收速率显著增加;低浓度硅素处理并未对根冠比产生显著影响,高浓度硅素处理显著增加了根冠比;叶片相对电导率随着硅素水平的增加而呈现先降低后增加的趋势。当硅素浓度达到0.5 mmol·L~(-1)时,叶片相对电导率最低;随着硅素浓度的增加,草地早熟禾根系总表面积和总长逐渐增加;根系直径随着硅素水平的增加而呈现先增加后降低的趋势,硅素浓度为0.5 mmol·L~(-1)时,根系直径最大,当硅素浓度达到1.0 mmol·L~(-1)时,根系直径显著降低;在低浓度硅素处理下,根条数变化不大,当硅素浓度达到0.5 mmol·L~(-1)时,根条数显著增加。可见,适宜浓度的硅素处理有利于草地早熟禾硅素的吸收和根系生长。     

低温对玉米苗期根系生长及磷养分吸收的影响

利用盆栽实验研究了低温对春玉米苗期根系生长、根际和非根际土壤磷的有效性及玉米磷吸收的影响。结果表明,低温抑制了玉米根系的生长,降低了玉米对磷的吸收。同时,低温胁迫下玉米苗期根际和非根际土壤有效磷均低于对照,且根际土壤磷素与非根际土壤磷素没有明显差异。     

Comparison of Arsenic and Phosphate Uptake and Distribution in Arsenic Hyperaccumulating and Nonhyperaccumulating Fern

Abstract

Uptake of arsenic (As) and its distribution in Chinese Brake fern (Pteris vittata L.), an As hyperaccumulator, and Boston fern (Nephrolepis exaltata L.), a nonhyperaccumulator, in the presence of phosphorus (P), were characterized by employing a hydroponic experiment with a complete three-factorial design. Two levels of As (100 and 1000 µM) and four levels of P (0, 100, 500, and 1000 µM) were used in this study. Arsenic uptake rates on the basis of root fresh weight for the two ferns were similar at low As concentration (100 µM). At high As concentration (1000 µM), however, As uptake rates (373–987 nmol g^?1 f wt h^?1) of P. vittata were significantly greater than those of N. exaltata (164–459 nmol g^?1 f wt h^?1). In both ferns, addition of P reduced their As uptake rate as well as accumulation. Pteris vittata had a greater As TF (Translocation factor = concentration ratio of fronds to roots) than N. exaltata. On the contrary, N. exaltata displayed a greater P TF than P. vittata. As a result, high P/As ratio was observed in the roots of P. vittata, whereas high P/As ratio was observed in the fronds of N. exaltata. The study illustrated that As hyperaccumulation by P. vittata may be facilitated by its high As influx rate and its high molar P/As ratio in the roots resulting from both high As TF and low P TF.     

主要环境因子对孔石莼净水作用的影响 (Ⅰ)对氨氮吸收的影响

研究了温度、光照和ｐＨ对孔石莼吸收氨氮的影响。孔石莼对氨氮吸收的最佳温度为２５℃，最适温度范围为２０～３０℃；光照对吸收速率的影响较小，当光强＞５０００ｌｘ时，吸收即达到饱和；养殖水体的ｐＨ（８．０～８．３）有利于孔石莼对氨氮的吸收。     

温室黄瓜磷素吸收与分配动态模拟

依据温室黄瓜磷素吸收、分配与温度、辐射的关系,构建了基于辐热积的温室黄瓜磷素吸收与分配模型,并利用与之相独立的试验资料对模型进行了检验。结果表明：模型对温室黄瓜磷素总吸收量的预测结果与1∶1直线之间的决定系数为0.91,均方根差为0.04g/株;根、茎、叶、果实磷素质量分数决定系数分别为0.74、0.65、0.72、0.65,均为根差分别为0.03%、0.04%、0.02%、0.06%。模型对不同季节温室黄瓜磷素吸收量与各器官磷素含量的预测值与实测值较为一致。     

The effect of high ortho-phosphate water levels on growth,feed intake,nutrient utilization and health status of juvenile turbot (Psetta maxima) reared in intensive recirculating aquaculture systems (RAS)

In intensive recirculating aquaculture systems (RAS) ortho-phosphate (ortho-P) is one of the main accumulating substances, but effects of chronically elevated concentrations on fish health and production performance are still unknown. Therefore 120 juvenile turbot (Psetta maxima) were exposed to ortho-P concentrations of 3 mg/L (control – C), 26 mg/L (low – LP), 52 mg/L (medium – MP) and 82 mg/L (high – HP) for 56 days and fed until satiation with a commercial diet. Health status and feed conversion ratio (FCR) were not significantly affected by treatment (p > 0.05). Specific growth rates (SGR) and daily feed intake (DFI) of C were not considered significantly different from LP, MP and HP treatments, however LP showed significant higher DFI and SGR than HP (p < 0.05). Using non-linear regression between SGR and ortho-P concentrations, 27 mg/L ortho-P was found as the optimum for turbot growth. Although not reflected in blood plasma P levels (p > 0.05) a potential aqueous P uptake might result in metabolic benefits leading to the observed growth enhancement in the LP treatment.In a second experiment 114 juvenile turbot were exposed to ortho-P concentrations of 2 mg/L (C2) and 25 mg/L (LP2) for 63 days and fed until satiation with a low P diet (4.6 g digestible-P/kg diet). Overall production performance was low due to low voluntary feed intake. Whereas the FCR was unaffected by treatment (p > 0.05), significantly higher feed intake and biomass gain were observed for LP2 compared to C2 (p < 0.05). LP2 treatment showed a trend for higher protein retention efficiency and lower whole body lipid content (p < 0.1). The dry matter, ash, Phosphorus, Calcium and protein content in whole body did not significantly vary between treatments (p > 0.05).In conclusion the accumulation of ortho-P in RAS does not negatively affect health of turbot. Elevated ortho-P seems to have slight positive effects on production performance of juvenile turbot. Further research to quantify dietary P requirements for turbot in general, as well as for turbot raised under elevated ortho-P conditions in RAS is strongly required.     

盐胁迫对燕麦幼苗Na+、K+吸收和离子积累的影响

为了解盐胁迫下燕麦幼苗Na~+、K~+吸收和离子积累规律,以燕麦品种中耐盐性较强的Vao-9和耐盐性较弱的白燕5号为试验材料,用离子流检测技术研究了70 mmol·L~(-1)盐(NaCl和Na_2SO_4摩尔比1∶1混合)胁迫0、24、48和72 h后,幼苗根系Na~+、K~+流速、流向,并测定根、茎、叶中Na~+、K~+、Ca~(2+)、Mg~(2+)积累量。结果表明,盐胁迫48 h后,根系Na~+外排速率显著增加(P0.05),且Vao-9的Na~+外排速率显著高于白燕5号;K~+外排速率随胁迫时间的延长呈增加趋势,Vao-9的K~+外排速率显著低于白燕5号;燕麦在盐胁迫下体内Na~+增加,K~+下降,Ca~(2+)、Mg~(2+)变化不明显,但各器官中4种离子分配有差别;盐胁迫72 h时,Vao-9叶中Na~+分配较白燕5号少5.2%,茎中多7.4%;Vao-9叶和茎中K~+分配较白燕5号分别多4.4%和2.5%,Ca~(2+)分配分别多3.5%和3.8%;叶片Ca~(2+)积累量增加且Vao-9始终大于白燕5号,两品种茎中Ca~(2+)、Mg~(2+)积累量在胁迫72 h时差异显著,Vao-9叶中Na~+/K~+、Na~+/Ca~(2+)、Na~+/Mg~(2+)值均较白燕5号低。这说明较强的Na~+外排能力和K~+保持能力以及离子在植株各器官的合理分配是耐盐品种适应盐胁迫的重要途径。     

Influence of oxygen on production and consumption of nitric oxide in soil

Summary NO and N₂O release rates were measured in an acidic forest soil (pH 4.0) and a slightly alkaline agricultural soil (pH 7.8), which were incubated at different O₂ concentrations (<0.01 – 20% O₂) and at different NO concentrations (40 – 1000 ppbv NO). The system allowed the determination of simultaneously operating NO production rates and NO uptake rate constants, and the calculation of a NO compensation concentration. Both NO production and NO consumption decreased with increasing O₂. NO consumption decreased to a smaller extent than NO production, so that the NO compensation concentrations also decreased. However, the NO compensation concentrations were not low enough for the soils to become a net sink for atmospheric NO. The release of N₂O increased relative to NO release when the gases were allowed to accumulate instead of being flushed out. The forest soil contained only denitrifying, but not nitrifying bacteria, whereas the agricultural soil contained both. Nevertheless, NO release rates were less sensitive to O₂ in the forest soil compared to the agricultural soil.     

石灰性土壤中几种蔬菜幼苗吸钾特点的研究

本文选用8种蔬菜作物在两种石灰性土壤上进行幼苗耗钾试验,以探讨不同蔬菜作物在苗期的吸钾特点。试验结果表明,各种蔬菜作物吸钾和耐钾饥饿的能力有明显的差异。在耗钾试验中,作物吸收的钾绝大部分来自土壤非交换性钾,其中 1M热HNO_3一次不能提取的非交换性钾部分最高可达55％,其数量随种植次数及作物吸钾总量的增长而提高。     

蛋鸡离休小肠细胞对类胡萝卜素吸收的研究

利用体外法研究了浓度、温度、吐温２０（Ｔｗｅｅｎ２０,下同）、根皮素对鸡离体小肠细胞对黄体素和一切萝卜素吸收的影响。结果表明：黄体素和胡萝卜素的吸收呈浓度依赖性,培养温度对两者吸收无影响（Ｐ＞０．０５）。蛋鸡离体小肠细胞对两者的吸收方式可能为被动扩散;Ｔｗｅｅｎ２０抑制了两种类胡萝卜素的吸收,其中对黄体素抑制作用较大;根皮素促进黄体素的吸收而抑制胡萝卜素的吸收。另外对蛋黄中色素分析发现其中主要沉积叶黄素。