Partitioning of Carbohydrates in Annual and Perennial Cotton (Gossypium hirsutum L.)

An analysis of the partitioning of carbohydrates in annual andperennial cotton was made to ascertain the distribution of assimilatesand constitution of reserves. Root/shoot dry matter ratio ishigh in perennial cotton and this plant shows a preferentialaccumulation of dry matter in roots corresponding to its adaptationto drought. Starch content is also higher in perennial cottonroots than in annual. It can be said that the earlier maturingthe cultivar, the lower the root/shoot ratio and the lower thestarch content. Nevertheless, at the whole plant level in annualcotton the starch content is highest in leaves where it is accumulatedbefore migration, and stem wood, and lowest in root and bark.While starch content in roots of annuals declines after 3 months,it is still increasing in perennials. Accumulation of carbohydratesas reserve material can be modified by selection and such selectionis accompanied by an increase in the activities of ß-amylasein exporting organs: leaves, woody tissue of the stem, and barkbut not in roots. Invertase activities were highest in leavesbut did not respond to selection. Non-irrigated cotton had ahigher activity of ß-amylase in leaves and stem woodcorresponding to the mobilization of reserve assimilates. Smallerincreases were observed in the activity of invertase. High yieldingannual cottons show a higher activity of ß-amylaseand invertase in leaves corresponding to a higher capacity ofassimilate transfer. Also a comparison was made from emergenceto 4 months of the partitioning of carbohydrates between leaf,stem and roots in annual and perennial cotton. In conclusionperennial cotton apparently owes its drought resistance to apartitioning of assimilates that favours the growth of the rootsystem and the accumulation of starch reserves in roots. Key words: Gossypium hirsutum L, carbohydrates, partitioning     

Cyanide-resistant Respiration and Cold Resistance in Seedlings of Maize (Zea mays L.

Respiratory activity of mitochondria isolated from seedlingsof two cold-resistant and two cold-susceptible maize cultivarswas examined. The greater potential for cyanide-resistant respirationfound in the cold-resistant seedlings raises the possibilityof a role for the alternative respiratory pathway in cold-resistance. alternative respiration, cold-resistance, cyanide-resistant respiration, maize, mitochondria, Zea mays     

华北落叶松夜间树干液流特征及生长季补水格局

在宁夏六盘山北侧半干旱区的叠叠沟小流域,采用热扩散探针法在2011年生长季监测了华北落叶松(Larix principisrupprechtii)人工林的树干液流速率,分析了夜间树干液流和补水量的变化特征及与气象、土壤水分等环境因子的关系.结果表明:树干液流速率日变化表现为典型的单峰宽峰曲线,且整个生长季均存在微弱的夜间液流,一般表现为逐渐减小,特别是在晴天,且晴天的变幅显著大于雨天.除生长季中期雨天夜间液流平均速率显著高于晴天,生长季初期及末期雨天与晴天的差异并不显著.生长季内,夜间树干补水总量为11.03 mm,占总蒸腾量的7.22％;5月份的树干补水量最大(4.19mm),其他月份的树干补水量明显减小,在0.9-1.7mm的范围波动.但不同月份间的补水贡献率存在明显差异,表现为生长季末期(9、10月)＞初期(5月)＞中期(6-8月).相关分析表明,日补水量与各气象因子关系不大,仅与降水量显著正相关(P＜0.05),与土壤含水率、日间蒸腾量、日蒸腾总量极显著正相关(P＜0.01).夜间补水的月蒸腾贡献率与月均土壤含水率、月均气温、月均日间蒸腾量、月总蒸腾量等显著相关(P＜0.05);而夜间补水的日蒸腾贡献率与日最高气温、日均气温、日间蒸腾量、日均饱和水汽压差、日总蒸腾量、日均太阳辐射强度、日最低气温、日均空气相对湿度、日降水量、土壤含水率等极显著相关(P＜0.01),经逐步回归分析建立了日补水量蒸腾贡献率与环境因子的多元线性模型.     

Homalodontus nom. nov., a replacement name for Wapitiodus Mutter,de Blanger and Neuman, 2007 (Homalodontidae nom. nov., ?Hybodontoidea), preoccupied by Wapitiodus Orchard, 2005

The replacement names Homalodontus nom. nov. ( Homalodontidae nom. nov. ) are proposed for the Early Triassic shark Wapitiodus Mutter et al., 2007 (Wapitiodidae Mutter et al., 2007), preoccupied by the Triassic conodont Wapitiodus Orchard, 2005 (Gondolellidea Lindström, 1970 ). © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 419–420.