Oxygen isotope ratios of plant available phosphate in lowland tropical forest soils

Phosphorus (P) cycles rapidly in lowland tropical forest soils, but the process have been proven difficult to quantify. Recently it was demonstrated that valuable data on soil P transformations can be derived from the natural abundance of stable oxygen isotopes in phosphate (δ¹⁸O_P). Here, we measured the δ¹⁸O_P of soils that had received long-term nutrient additions (P, nitrogen, and potassium) or litter manipulations in lowland tropical forest in Panama and performed controlled incubations of fresh soils amended with a single pulse of P. To detect whether δ¹⁸O_P values measured in the incubations apply also for soils in the field, we examined the δ¹⁸O_P values after rewetting dry soils. In the incubations, resin-P δ¹⁸O_P values converged to ∼3.5‰ above the expected isotopic equilibrium with soil water. This contrasts with extra-tropical soils in which the δ¹⁸O_P of resin-P matches the expected equilibrium with soil water. Identical above-equilibrium resin-P δ¹⁸O_P values were also found in field soils that did not receive P additions or extra litter. We suggest that the 3.5‰ above-equilibrium δ¹⁸O_P values reflect a steady state between microbial uptake of phosphate (which enriches the remaining phosphate with the heavier isotopologues) and the release of isotopically equilibrated cell internal phosphate back to the soil. We also found that soil nutrient status affected the microbial turnover rate because in soils that had received chronic P addition, the original δ¹⁸O_P signature of the fertilizer was preserved for at least eight weeks, indicating that the off-equilibrium δ¹⁸O_P values produced during microbial phosphate turnover was not imprinted in these soils. Overall, our results demonstrate that ongoing microbial turnover of phosphate mediates its biological availability in lowland tropical soils.     

不同施磷方式对海岛棉农艺性状及产量的影响

在新疆生态条件下,采用海岛棉新海35号研究同等用量3种施磷方式(犁地前全部撒施、犁地前撒施50%与作种肥施50%和全部作种肥施)对棉花农艺性状及产量的影响。结果表明:施磷方式对棉花生育进程的影响较小,各处理对新海35号棉花的农艺性状没有显著性的影响,P1处理可略为提高棉花花铃期叶面积指数,其中P1处理会略提高棉花后期的干物质积累量,以P1、P2处理的方式施磷肥,棉花的单株结铃数可提高4%~7%皮棉产量可提高12%~14.8%。     

磷肥对甘肃临夏地区燕麦干草及种子生产的影响

为确定甘肃高寒雨养区燕麦(Avena sativa)种子生产中磷肥最佳用量,提高肥料利用效率,试验在氮肥(尿素)用量75 kg·hm^-2的固定水平下,设计4个磷肥(P₂O₅)水平(0(CK),65(C₁),100(C₂),135(C₃)kg·hm^-2),对各磷肥水平下干草产量、种子产量和相关性状的变化进行了研究。结果表明：施用磷肥使燕麦的株高、茎粗、分蘖和干草产量均有提高,灌浆期C₁,C₂,C₃干草产量较CK依次提高13.85%,25.96%,22.65%,干草产量与磷肥水平显著正相关(相关系数0.91);施用磷肥提高了燕麦的有效分蘖数、主穗长,显著提高主穗粒数、穗粒重、千粒重、种子产量和秸秆产量,C₁,C₂,C₃种子产量较CK依次提高12.37%,16.72%,14.38%,种子产量与磷肥水平显著正相关...     

利用32P示踪研究马铃薯(合作-88)对磷素营养的吸收及分布规律

应用3 2 P研究“合作 88”马铃薯对磷素营养的吸收和分布规律 ,结果显示 :马铃薯对磷素营养的吸收率随植株的生长而增加。吸收率与栽培生长时间呈显著正相关。磷素主要分布为茎 >根 >叶 ,随生育期茎中含量相对增加 ,而叶中含量相对减少 ,根的不变。     

植物Pht1家族磷转运子的分子生物学研究进展

植物磷转运子是植物磷营养中的重要蛋白之一。对植物磷转运子蛋白的拓扑结构、功能及其基因的调控和表达位点的研究,揭示了植物磷转运子各家族中各成员在磷代谢中的角色。植物磷转运子中Pht1家族是一类H2PO4-/H 共转运子,该家族主要成员在植物根系中负责磷的吸收、转运,其表达受磷调控,因此是研究得最为深入的植物磷转运子家族。本文总结了植物Pht1家族磷转运子的最新研究进展,讨论了植物磷转运、分配的分子机理,并指出今后研究的主要方向,为开拓改良植物磷效率的新思路提供依据。     

植物对磷饥饿的反应研究进展

磷是构成生命的重要元素之一,也是土壤中有效性最低的一种营养元素。我国是世界上最大的小麦生产国。但是我国耕地中有59%的土壤缺磷。农作物的产量常受到缺磷的影响而受损。土壤缺磷并不是土壤中总磷量低,而是土壤中可供植物直接吸收利用的有效态磷含量低。植物在磷饥饿时会发生各种各样的变化,以尽最大可能满足自身对磷的需求。植物对缺磷的反应是一个复杂的网络过程。大约有100多个基因参与了植物对缺磷的反应。其中主要的有磷转运蛋白基因、核糖核酸酶基因、磷酸酶基因等。植物在吸收外界的磷的过程中磷转运蛋白发挥了重要作用。植物磷转运蛋白基因按照序列相似性可以划分为H+/Pi共转运家族(Pht1家族)和Na+/Pi共转运家族(Pht2家族)。按照吸收动力学的标准可以分为高亲和力磷转运蛋白和低亲和力磷转运蛋白两种。磷饥饿时植物对磷吸收能力的增强的原因之一是增加了磷转运蛋白分子的合成数目。目前尽管人们对植物吸收磷的理解已经有了长足的进步,但是在植物对磷的具体调控机制、磷的跨液泡膜运输等重要方面仍然没有明确的结果。     

棉花不同品种叶片和纤维中蔗糖磷酸合成酶活性变化 及其与糖含量的关系

利用山农棕02、丰抗6号、中棉45 3个品种在大田栽培的条件下，研究了叶片和纤维中蔗糖磷酸合成酶活性的变化及与糖含量的关系。结果表明，在3个品种的叶片和纤维中，蔗糖磷酸合成酶活性均出现双峰，在开花当天最高，花后18d次之，整体呈下降趋势；与此同时可溶性总糖和蔗糖的含量变化以及光合速率的变化也成相似的变化。3个品种中，丰抗6号蔗糖磷酸合成酶活性和含糖量最高，中棉45次之，山农棕02最低。3个品种的相应观测指标之间均呈极显著差异。     

氮磷钾施肥比例对枣幼树生长、结果和果实品质的影响

 以‘大瓜枣’为试材，用盆栽试验研究了氮磷钾施肥比例对枣幼树生长、结果和品质的影响，结果表明，氮磷钾比例为2∶1∶2时，生长中庸，树形结构合理，可显著提高坐果和产量。氮磷钾比例为2∶1.5∶3时，可显著促进生长，较丰产，可溶性固形物含量高,两种比例均可作为施肥参考。施用有机肥可增进品质。     

三种鲟鱼血清及组织中磷酸酶和补体活性的比较

对施氏鲟、小体鲟和西伯利亚鲟的血清、肝脏、鳃及肠中碱性磷酸酶(AKP)、酸性磷酸酶(ACP)、补体C3及补体C4活性进行了测定和比较.AKP活性在小体鲟鳃和肠中显著高于施氏鲟和西比伯利亚鲟(P＜0.05),而其在三种鲟鱼的肝脏和血清中差异不显著(P＞0.05);ACP活性在小体鲟肠中显著高于施氏鲟和西比伯利亚鲟(P＜0.05),而其在三种鲟鱼的肝脏、鳃和血清中差异不显著(P＞0.05);补体C3活性在小体鲟肝脏和肠中显著高于施氏鲟和西比伯利亚鲟(P＜0.05),而其在三种鲟鱼的鳃和血清中差异不显著(P＞0.05);小体鲟血清中补体C4活性显著高于施氏鲟和西伯利亚鲟(P＜0.05),而补体C4活性在三种鲟鱼的肝脏、鳃及肠中差异不显著(P＞0.05).由此可见,虽然三种同为鲟科鲟属鱼类,但它们之间的AKP、ACP、补体C3及补体C4活性存在着种间差异.     

Dual and Triple Intercropping: Potential Benefits for Annual Green Manure Production

Abstract

Greater species diversity in natural ecosystems increases plant biomass production and stability. Intercropping is an agricultural practice that aims to accrue the benefits of species diversity by growing two or more species simultaneously in the same space. Functional group diversity is considered important for enhancing the beneficial effects of species diversity, but most previous intercropping studies used combinations of only two functional groups. Thus, we used three green manure species from different functional groups: sorghum (Sorghum bicolor (L.) Moench.), a C4 grass; crotalaria (Crotalaria juncea L.), a legume; and sunflower (Helianthus annuus L.), a forb. We examined the effects of intercropping on biomass, nutrient uptake, and their stability using a proportional replacement series in a field experiment for three years with four trials. The aboveground biomass was higher with dual and triple-component intercrops compared with sole crops; however, there were no superior effects of triple-component intercropping over dual-component intercropping. There were also no clear advantages of intercropping in terms of the nutrient uptake amount and stability.