Coarse bed material patch evolution in low-order,ephemeral channels

In river channel beds composed of a wide range of grain sizes, the bed material is often arranged in discrete patches discernable by relative texture. These bed material patches are the primary source of entrainable coarse sediment within the channel system and their composition and size have been found to influence the composition and rate of sediment transport. Twelve coarse (gravel–cobble) sediment patches distributed throughout the channel network within a 4.53 ha watershed in southeastern Arizona were monitored for 2 years. Changes in patch area and grain size were measured and painted patch grains were monitored to confirm that patch grains were mobilized during flow. Individual coarse bed material patches exhibited variable persistence during flows with return frequencies ranging from approximately 1 year to 4.6 years. While no patch fully dispersed during the study period, two new patches formed. Most coarse patches remained relatively stable in area and grain-size distribution despite the entrainment of patch grains as lost grains were sufficiently replaced with sediment from upstream. Because of the grain replacement process and the effect of other sediment supply dynamics, the changes in patch area and grain-size distribution display a complex relationship with the magnitude of predicted grain mobilization within each patch. Results indicate that relative stability varies from patch to patch, influenced by the balance of patch grains transported out of the patch and the deposition of new grains into the patch. Predictive models of coarse sediment transport and yield that assume the channel bed is a fixed source of sediment supply may not adequately capture the sediment dynamics within patchy channel beds and should be used with caution when applied to these environments due to the possibility of patch instability as documented in this study.     

高等植物对钠离子的吸收、运输和累积

综述了植物对钠离子吸收、运输和累积等方面的最新研究进展。植物根系吸收钠离子的途径可能有三条,包括2条跨膜途径(钙敏感和非钙敏感两部分)和支流途径等。根系对钠离子的吸收可能是被动的,但排泄是主动的。木质部的装载可能是主动的,也可能是被动的。木质部的卸载过程还不清楚,可能是通过非选择性阳离子通道,或K /Na ,Na /H 反向运输体完成。Na 在植物体内运输需要特殊部位特殊细胞类型以协同方式运作。为了减少Na 通过木质部的质外体部分向地上部输送,根系靠外的部分细胞要减少流入,而内层细胞应该加大流入。我们需要了解更多的特殊细胞运输过程,和特殊细胞的载体及信号操作过程的知识。     

运输应激对AA肉鸡组织结构的影响

集约化养殖的畜禽进出养殖场和屠宰前都必须经过运输,运输过程中由于捕捉、挤压、断水、断食、噪音及过度疲劳等原因所造成的运输应激会导致动物的生理、心理状态和代谢过程发生相应地变化,严重时甚至会死亡,给畜牧业生产带来巨大损失。本试验利用组织学及病理学方法研究了不同的运输时间对AA肉鸡不同组织造成的影响。选取生长状况相似健康的7周龄AA肉鸡40只,随机分成4组,每组10只,分别运输2h、3h、4h和5h,结束后立即剖杀,取心、肝、脾、肺、肾、胸腺等不同组织置于10%甲醛中,H-E染色光学显微镜下观察并拍照。结果表明:运输应激初期(2h)多数组织出现毛细血管扩张充血、细胞肿胀等急性病理性变化。运输3h到4h各组织的病理改变与初期相似但有所加重,运输5h心脏出现了心肌纤维的断裂,胸腺、脾、肾出现了功能衰竭等现象。由此可见,运输应激可导致组织细胞应激性损伤,并且组织损伤的程度随着运输时间的延长而有所波动。     

水稻植株状况对甲烷传输速率的影响及其品种间差异

以不同水稻品种为材料,通过实验室手段测定各品种水培稻株甲烷传输速率,研究水稻品种间甲烷传输能力的差异及原因;通过控制甲烷排放路径,研究水稻植株状况对甲烷传输的影响。结果表明i在品种演进过程中,稻株甲烷传输速率逐渐增大(南京1号偏小除外),根氧化力与甲烷传输速率趋势一致。苗期甲烷有50％是经叶片传输的;剪根后甲烷传输速率随之改变,留根条效、根重与甲烷传输速率的变化均呈明显的线性正相关。植株茎蘖效对甲烷传输有影响,在一定的范围内,植株茎蘖越多,甲烷传输速率越大。这说明根氧化力是造成品种间甲烷传输速率不同的主要原因。植株生长健壮,叶片多,根系发达,茎蘖多,植株甲烷传输速率大。     

冻融作用对土壤胶体及胶体结合态铅迁移的影响

以东北地区棕壤为研究对象,通过人工控温和土柱淋洗试验,研究了不同冻融处理下铅污染土柱中土壤胶体和胶体结合态铅的迁移特征。结果表明:土壤高含水量(田间持水量100%)条件下冻融作用促进土壤胶体的迁移;土壤低含水量(田间持水量10%)条件下冻融作用对土壤胶体的影响减弱。淋洗试验中,土壤胶体在前20 min内大量淋失出土体,随后淋失量急剧减少;且前20 min内的土壤胶体淋失量随着冻融次数的增加先增加后减少。污染土柱中铅主要以胶体结合态的形式迁移,其迁移特征和受冻融作用影响的趋势与土壤胶体类似。冻融处理后滞留在土柱深层的铅含量较高,表明冻融作用能够促进铅向深层土壤迁移。     

钼提高植物抗逆性研究进展

钼（Mo）作为植物必需的微量元素,在促进植物生长发育和增强植物抗逆性方面发挥着关键作用。植物对钼的吸收转运主要受到钼酸盐转运蛋白基因MOT1和MOT2调控,钼进入植物体内以含钼酶形式参与植物生长代谢,其中对植物抗逆性方面的调控主要表现为：钼通过含钼酶硝酸还原酶、醛氧化酶、黄嘌呤脱氢酶影响植物体内的光合碳氮代谢、激素合成和活性氧代谢进而调控植物抗寒性;钼通过硝酸还原酶和醛氧化酶介导的信号转导过程调控根系发育、养分水分利用及抗旱基因表达,进一步影响脂质合成与代谢调控植物抗旱性;最新研究还发现钼在植物适应盐胁迫、缓解重金属胁迫方面也具有重要作用。这些研究结果为通过钼营养调控提升植物的抗逆性提供了新思路。     

Impacts of Municipal Wastewater on The Transport Characteristics of Reactive Solutes Through Agricultural Soils

Reliable transport parameters of agrochemicals and soluble pollutants are crucial for modeling and management of soil and groundwater quality. This study investigated impacts of municipal wastewater on the transport parameters of five heavy metal/metalloid compounds (NaAsO₂, Cd(NO₃)₂, Pb(NO₃)₂, Ni(NO₃)₂ & ZnCl₂), two pesticides (cartap & carbendazim) and an inert salt (CaCl₂) in four agricultural soils of Bangladesh. Solute-breakthrough concentrations were measured in repacked soil columns with time-domain reflectometry (TDR) both before and after wastewater treatment. Transport velocity (V), dispersion coefficient (D), dispersivity (λ) and retardation factor (R) of the solutes, and pertinent soil properties were determined. Wastewater reduced bulk density (γ) of the soils (from 1.32–1.37 g/cm³ to 1.26–1.35 g/cm³) by increasing organic carbon (OC) (from 0.37%–0.84% to 0.40–0.93%), increased pore-size distribution index (n) (by 0.02 unit) and reduced soil pH (from 6.32–7.45 to 5.92–6.46). D and λ decreased while V and R increased after wastewater treatment; D decreased and R increased linearly with decreasing bulk density. The correlations of V, D, and R with n improved significantly (p < 0.05) after wastewater treatment. The correlation between λ and OC improved markedly for Ca, Pb, Ni, and cartap. The observed indicative results have practical implications in developing pedo-transfer functions for solute-transport parameters using basic soil properties, which are subject to progressive modification due to agrochemicals application and wastewater irrigation.     

涌泉根灌湿润体水氮运移特性试验研究

在陕北米脂山地微灌枣树示范基地原状土上进行了涌泉根灌肥液入渗试验,研究了湿润体特征值的变化规律及水氮运移特性.〖JP+1〗结果表明：涌泉根灌入渗能力随肥液质量浓度增大而增大,累积入渗量与入渗时间的关系符合Kostiakov模型;竖直剖面的水平和垂直方向上的湿润锋运移速度均随肥液质量浓度增大而增大,并与时间均呈良好的幂函数关系.肥液质量浓度越大,涌泉根灌相同时间内湿润体的湿润深度越深,相同位置处的土壤质量含水率越大.清水与不同肥液质量浓度的涌泉根灌土壤平均质量含水率分布规律类似,肥液质量浓度越大,相同土层深度的质量含水率越大.在一定施肥条件下,涌泉根灌肥液入渗相同深度处NO-3-N与NH+4-N质量比均随肥液质量浓度增大而增大,经过水分再分布,均于土层深度70 cm处接近本底值.     

蚯蚓粪对土壤团聚体组成和入渗过程水分运移的影响

通过室内土壤团聚体组成分析试验和土柱一维垂直入渗试验,探究蚯蚓粪对土壤团聚体组成、抗水蚀稳定性以及入渗过程中水分运移特性的影响。结果表明:(1)蚯蚓粪可以有效降低土壤容重,增加0.25~2 mm粒级大团聚体的数量,分形维数D从2.84减小至2.65,减小了6.69%,显著提高了土壤团聚体抗水蚀稳定性;(2)施加比例为1/20时,可以显著增加湿润锋的运移距离,而后随着施加比例的增大,湿润锋距离有不同程度的减小,但均大于未施加蚯蚓粪的处理,且各处理下的湿润锋运移距离与入渗时间的关系均可用幂函数描述;(3)蚯蚓粪比例的增大可以显著提高累积入渗量和稳定阶段的入渗速率,当施加比例为1/3时,累积入渗量较对照组增大48.74%;其中Kostiakov-Lewis模型对入渗过程的模拟准确度最高,也更接近实测值。     

马尾松幼苗光合产物的运输与分配特征

【目的】解析光合产物在马尾松幼苗植株中的运输和分配规律,揭示马尾松生产力形成过程,为探讨不同环境干扰下马尾松光合产物分配过程的变化提供参考依据。【方法】采用 13 C同位素脉冲标记法,对1.5年生马尾松幼苗进行标记,标记结束后第0、2、5、17、24、72、120、168、216和 360 h ,按不同部位对马尾松幼苗进行全收获取样,测定 13 C含量,以监测近期合成的光合产物在马尾松幼苗中的运输和分配规律,同时测定光合产物全碳、非结构性碳水化合物(NSC)在各个器官的积累量。【结果】1)标记的光合产物在针叶中合成后,向各库器官的运输量随着时间延长由多逐渐减少,具体表现为标记结束后0~24 h内最多,24~216 h逐渐减少,216 h之后运输完成,且59%以上标记的光合产物在0~24 h内运输到各库器官。2)光合产物运输趋于稳定后,在各器官的分配大小依次为1年生叶>当年生叶>根>茎干>1年生枝>当年生枝,与生物量的分配大小一致,但与库活力大小不同,其库活力依次为当年生叶>当年生枝>1年生叶>根>1年生枝>茎干。3)各器官全碳和NSC积累量的分配与近期合成光合产物的分配大小一致,依次为1年生叶>当年生叶>根>茎干>1年生枝>当年生枝。【结论】马尾松幼苗光合产物运输速率大于0.1 m ·h -1 ,59%以上标记的光合产物在合成后的0~ 24 h 内完成向各个库器官输出。新合成的光合产物在各器官中的积累量表现为功能器官(叶和根)居多,这一分配规律有利于马尾松幼苗阶段的生长。