一氧化氮（NO）在硝酸盐调节玉米根伸长中的作用

植物根系大小和形态是决定植物吸氮能力的重要因素，而植物根系生长发育与土壤中营养元素的分布及其有效性密切相关，尤其是硝酸盐。然而目前关于硝酸盐调节植物根系生长的生理机制仍不清楚。一氧化氮（NO）是一种重要的气体信号分子，参与植物体内多种生理生化过程，包括调节根的生长发育。本研究以玉米自交系478为材料，采用营养液培养法，探讨了NO在硝酸盐调节玉米根系生长中的作用。主要结果和结论如下： 玉米幼苗在不同硝酸盐水平下生长7天后，主根伸长随着硝酸盐浓度的升高而下降;与0.01 mM硝酸盐处理下的玉米主根伸长相比，0.1 mM和1 mM硝酸盐处理对玉米主根伸长分别抑制了30%和36%。随着硝酸盐浓度的增加，玉米主根根尖过氧化氢（H2O2）含量表现出降低的趋势，而抗氧化酶，如超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）的活性则表现出增加的趋势。外源供应过氧化氢对低浓度硝酸盐（0.01 mM）和高浓度硝酸盐（10 mM）处理下的玉米根伸长都没有影响，这表明了根尖过氧化氢含量的下降不是高浓度硝酸盐抑制玉米主根伸长的原因。 NO供体硝普钠（SNP）能够缓解高浓度硝酸盐对玉米主根伸长的抑制，而对低浓度硝酸盐处理下的主根伸长没有影响，而且NO清除剂亚甲基兰（MB）和NO合成酶抑制剂Nω-硝基-L-精氨酸（L-NNA）显著抑制了低浓度硝酸盐处理下的玉米主根伸长，而对高浓度硝酸盐处理下的玉米主根伸长没有影响。用NO特异性荧光染料4,5-二氨基乙酰乙酸荧光素(DAF-2DA)检测结果表明：高浓度硝酸盐显著降低玉米根尖NO含量。而玉米根中的硝酸还原酶活性随硝酸盐浓度的增加而增加。以上结果说明，高浓度硝酸盐抑制玉米主根伸长可能是与根尖NO合成酶的下调所导致的内源NO含量的降低有关。 另外，外源生长素（IAA）能缓解高浓度硝酸盐对玉米主根伸长的抑制，同时，也增加了高浓度硝酸盐处理下玉米根中内源NO含量，而对低浓度硝酸盐处理下的玉米根中内源NO没有影响。因此推测，根尖生长素的下降导致内源NO含量的降低可能是高浓度硝酸盐抑制玉米主根伸长的原因。

Physical variables, nutrient status and primary productivity of Kyoga Basin lakes of Lemwa, Omunuo, Gawa, Adois and Owapet

The review report on Kyoga basin lakes (NAFIRRI 2007) described Kyoga basin lakes as important natural resource for the communities within the basin and the surrounding areas. Fisheries of the basin provide a source of protein, income, and employment to generally poor communities in the area. The lakes also generate revenue to the local Governments within the catchment. This indicates that the fisheries of Kyoga basin lakes are a key instrument in poverty eradication and food security. The lakes also act as a source of water for domestic, agricultural and transport purposes. Some of the Kyoga small lakes harbour fish species, which have disappeared from the main lakes Victoria and Kyoga and are therefore important for biodiversity conservation

Seasonal fluctuation in primary production in relation to the physicochemical parameters of two weed-infested ponds of Kalyani, West Bengal

Kalyani lake (P sub(1)), a weed infested recreational water body and a weed chocked derelict water body (P sub(2)) in the heart of Kalyani city of West Bengal were studied for a period of one year for their primary productivity and other physicochemical parameters. Very low primary productivity (GPP=360-1237mg C m super(-2) d super(-1); NPP=157-787 mg C m super(-2) d super(-1)) was recorded in P sub(2) in spite of having a high concentration of nutrients (PO sub(4)–P=0.052-0.260mg l super(- 1); NO sub(3)-N=0.110-0.412mg l super(-1)). On the other hand, moderate primary productivity (GPP=1687-3195mg C m super(-2) d super(-1); NPP=900-2700mg C m super(-2) d super(-1)) was found in P sub(1) with comparatively low range of nutrients (P0 sub(4)-P =0.010-0.058mg l super(-1); NO sub(3)-N=0.032-0.118mg l super(-1)). After studying the other physicochemical parameters (temperature, transparency, dissolved oxygen, free carbon dioxide, pH, alkalinity and macrophytic biomass), it was found that the overall hydro-biological conditions of the weed-chocked derelict water body (P sub(2)) is not congenial for biological production as compared to Kalyani Lake (P sub(1)). Kalyani Lake may be used for fish culture with proper management practices.

Growth performance and nutrient utilization of catfish Clarias gariepinus fed varying inclusion level of fermented unsieved yellow maize

This study was conducted using 150 fish of Clarias gariepinus to investigate the growth performance and nutrient utilization of Clarias gariepinus fed five treatment diets containing varying inclusion level of fermented unsieved maize. The diets were grouped into CT, T1, T2, T3, and T4 with inclusion levels of 25%, 50%, 75%, and 100% of fermented unsieved maize respectively. Highest weight gain was recorded in T4 with value of 10.24 and lowest weight was recorded in CT with 9.17. High FCR were observed in T2 with value of 0.70 and lower value was observed in T4 with value of 0.62. While, T2, T3, and T4 have highest survival rates with values of 90% in each treatment CT and T1 recorded 80% and 70% respectively. There was a significant (p< 0.05) difference between the food conversion ratios treatment T4 with the best value and other treatments. There was a significant (p< 0.05) difference between the levels of fermented unsieved maize inclusion and the specific growth rate of the experimental fish. The highest value of protein level and feed efficiency were observed in T4 at significant difference level (p< 0.05) than other treatments. It was concluded that fermentation of maize in fish feed has positive effects on the nutritional value of the feed. It is recommend that fermented maize can replace raw maize in fish feed diet for growth performance. KEYWORDS: Fermentation, yellow maize, Clarias gariepinus, Fish, Feed.