基于微根管技术的玉米根系生长监测

为了研究玉米根系生长规律,该文利用固城农业气象试验站内设置的大型根剖面系统,采用微根管观测法,对试验地上玉米主要生育期的根系生长动态进行定期直接跟踪监测,并以方形整段标本法作为参照标准,对试验数据采用MATLAB软件辅助图像处理和现代统计方法进行分析。结果表明：微根管法与方形整段标本法对得出的根长密度随深度增加呈递减型有较好的一致性,两者相关系数达到0.83以上,通过0.05的显著性检验;由观测数据建立的回归方程能较好地反映土壤中玉米根系生长规律,进一步表明微根管法是一种破坏性较小、可准确定位跟踪植物根系在土壤中生长动态变化的先进技术,对植物根系生长研究有较好的推广应用价值。     

Evaluating grassed waterway efficiency in southeastern Iowa using WEPP

Properly calibrated, single storm event, model simulations can be valuable quantitative tools for evaluating the effectiveness of grassed waterways (GWWs) and identifying a threshold length for an effective GWW. Current specifications for GWW lengths in Iowa are lacking. The key objective of this study is to employ the well-established Water Erosion Prediction Project model (WEPP) for determining an effective (or threshold) GWW length for reducing runoff and sediment yields under a wide range of hydrologic and management conditions in an agricultural Iowa watershed, namely Clear Creek, IA. The advantage of this physically based, distributed-parameter model is its ability to replicate processes at the hillslope scale where GWW performance is mostly evaluated. Overall, 84 WEPP runs were performed for assessing (i) the effect that GWW length has on reducing runoff and sediment yields within a representative test hillslope, and (ii) the effect of the gradient of the drainage area on GWW efficiency. Results show that the GWW efficiency for all GWW lengths is governed by hydrology, expressed as Q_peak. The results suggest that the threshold length for an effective GWW is 500 m for the hydrologic conditions in this study and for a representative drainage area of approximately 27 ha. For all storm events, a threshold drainage area gradient of approximately 3% was found above which the GWW efficiency was independent of topographic steepness. The results demonstrate similar trends to other studies although the relative increases in reduction in runoff and sediment delivery differ between sites and are very much dictated by Q_peak and hydrologic soil group. The effectiveness of models to evaluate GWW efficiency for nearly saturated conditions and shallow flows is discussed.     

Responses of Root Growth to Moderate Soil Water Deficit in Wheat Seedlings

Abstract

In the field, plants show better root growth in drying soil than in wet soil. However, the root growth enhancement has not been demonstrated clearly in the laboratory. In this study, the root growth response of wheat seedlings to moderate soil water deficits was characterized quantitatively in an environment-controlled chamber. Germinated seeds of wheat were grown for 15 days in the soil with a water potential ranging from field capacity (FC) to approximately –0.08 MPa. Theleaf area decreased with reduction in soil water potential. By contrast, the root surface area increased upon reduction ofthe soil water potential to –0.04 MPa while it decreased significantly in soil with a water potential of –0.08 MPa. The increase in surface area was obvious in the roots with a diameter of 0.2 to 0.4 mm and larger than 0.7 mm. Root weight increased with the reduction of soil water potential to –0.04 MPa. While specific root length decreased significantly with the reduction of water potential to –0.06 MPa, the specific root surface area did not. Assimilatestransported from shoot might be used in roots to increae the surface area mainly by increasing the diameter rather than the length in response to a moderate soil water deficit in wheat seedlings. This might result from the drought tolerance mechanism of osmotic adjustment in roots.     

Effects of Day Length and Air Temperature on Stem Growth and Flowering in Sesame

Abstract

The effects of day length and air temperature on the growth and flowering of sesame (Sesamum indicum L.) were examined to analyze the effect of seeding date on the seed yield. Short day (10-h light/14-h darkness) treatment decreased the final stem-length relative to natural day length (14.1～13.4-h), although it hardly affected the length of the stem-elongation period. The short-day treatment shortened the duration to the first flower and lowered the first flowering-node. It prolonged the flowering period, but decreased the flowering-node number on the main stem resulting from the slower rate of increase in nodes with flowers. Under a low day/night temperature condition (23/18ºC), the stem growth was very slow and flowering did not occur. As compared with a high temperature (30/23ºC), a low temperature (22/15ºC) during 15 days after emergence suppressed the seedling growth temporarily, but the seedlings resumed growth after the temperature treatment. The growth and flowering behavior after the treatment were unaffected by a low temperature during the seedling stage. On the other hand, a low temperature during the flowering period decreased the flowering-node number resulting from the slower rate of increase in nodes with flowers, although it prolonged the flowering period. In this study, the decrease in the flowering-node number by short days and low temperature was smaller than that by delay of seeding date as observed in our previous study. Thus, the effects of day length and air temperature were not the sole factors responsible for the effect of seeding date on the flowering-node number.     

Repeated annual drought has minor long‐term influence on δ13C and alkane composition of plant and soil in model grassland and heathland ecosystems

As a result of global climate change the incidence of drought conditions in Europe is predicted to increase in the future, which also influences plant resistance. Lipids are important plant constituents that protect plants against drought stress and contribute to the intermediate stable carbon (C) pool in soil. However, the extent to which drought influences lipid cycling in the plant–soil system is unknown and, therefore, it remains questionable how the ecosystem recovers after drought. We focused on plant and soil samples from two different plant communities (temperate grassland and heathland) that had been exposed to 5 years of 4.5–6.0 weeks repeated annual drought. They were sampled one year after the last drought to check the recovery of the plant–soil system. Samples were analyzed for their bulk C, stable C and nitrogen (N) isotope (δ¹³C, δ¹⁵N) and lipid composition. Contrary to our expectation, no strong influence of five years of repeated annual drought was observed for above‐ground biomass, roots and soils in the model ecosystems with respect to elemental (C and N concentrations, C : N ratio) bulk isotope (δ¹³C, δ¹⁵N) composition and the total extractable lipid concentration. Thus, plants did not sustain a significant change in their C and lipid concentration as well as their composition after five years of repeated annual drought. This might be related to the comparatively short drought period related to the overall growth season and provides evidence for recovery of the C and lipid dynamics in temperate grassland and heathland model ecosystems exposed to annual drought.     

关于非线性方程组求解技术

提出了新的非线性方程解法。在进行结构非线性平衡路径的全过程分析时，在仔细研究了由Ｃｒｉｓｆｉｅｌｄ和Ｒａｍｍ提出，并被广泛用于非线性方程求解的著名的弧长增量法的基础上，提出了一种基于牛顿－拉菲逊法的十分有效的投影增量法，该法克服了弧长增量法的一个重点缺点，即必须根据结构特性来判定如何选取关于广义荷载参数λ＾ｉ＋１的一元二次方程中的二个根中的一个，而且其收敛速度要稍快，计算量也略小。并通过引进广义时     

Influence of Day Length on Stem Growth,Flowering, Morphology of Flower Clusters,and Seed-Set in Buckwheat (Fagopyrum esculentum Moench)

Abstract

The effects of day length on main stem growth, flowering, morphology of flower clusters and seed-set were examined in three buckwheat cultivars Shinanonatsusoba (summer eco-type), Miyazakizairai (autumn eco-type) and BLO 1999 (a long cluster line which usually develops DM clusters at Kade Research Ltd., Canada). Long-day treatment prolonged the stem elongation period, elevated the first flowering node, delayed the first flowering day, increased the numbers of nodes, flower clusters and flowers on the main stem, and decreased the increase rate of flowering-cluster number, the number of seeds and the seed-set ratio on the main stem. It also increased the frequency of DM clusters, the length of the flower clusters and the number of sub-flower-clusters per cluster in Shinanonatsusoba and Miyazakizairai as well as in BLO 1999. The effects of day length varied among the growth parameters and there were three types of responses to day length. The difference between the summer and autumn eco-type cultivars in the responses to day length was elucidated in four groups of parameters; (1) main stem elongation; (2) first flowering node and first flowering day; (3) increase rate of flowering-cluster number on the main stem; and (4) the number of seeds and seed-set ratio.     

Interaction Between Plant Roots and Soil Water Flow in Response to Preferential Flow Paths in Northern China

Preferential flow is expected to provide preferential channels for plant root growth and variations in soil water flow, but few studies were conducted to imply the impacts of these changes, particularly for preferential flow in stony soils. This study aimed to characterize soil water flow and plant root distribution in response to preferential flow paths and quantitatively describe the relation between plant root distribution and soil water flow. Field dye‐tracing experiments centered on experimental plants were conducted to determine the root length density and soil water flow process. Laboratory analyses were performed to characterize changes in the relative concentration of the accumulated effluent and the degree of interaction between plant roots and soil water flow. The amount of fine plant roots with preferential flow paths decreased with increasing soil depth for all experimental plots. The largest plant roots were recorded in the upper soil layers to a depth of 20 cm. The relative concentration of the accumulated effluent increased with time and decreased with soil depth under saturated soil conditions, whereas a distinct early turning point for the relative concentration of the accumulated effluent was observed in the 0–20‐cm soil columns, and the relative concentration of the accumulated effluent initially decreased and then increased with time under unsaturated soil conditions. This study provides quantitative information with which to characterize the interaction between plant roots and soil water flow in response to preferential flow paths in soil–plant–water systems. Copyright © 2016 John Wiley & Sons, Ltd.     

蓝桉、直干桉子测林木材纤维长度的变异

在桉树种子园的后代测定林内，从蓝桉和直干桉中各抽3个家系，分别在立地条件不同的区组中按径阶等距抽样，每家系32株。经分析发现，纤维长度的变异为样品内>家系内>家系间。蓝桉纤维长度差异在径级和家系间均达到0．05水平，直干桉则不显著。区组间，两个树种的纤维长度差异都不显著。在立地条件好的区组中纤维长度与生长性状显著相关，立地条件差的区组却不密切。但以全部样本按树种分析，纤维长度与树高、胸径等生长性状都呈显著的正相关。     

盐度对蒙古裸腹(Moina mongolica Daday)耗氧率的影响

分别测定了５‰、１０‰、２０‰、３０‰、４０‰盐度下不同体长的蒙古裸腹氵蚤的耗氧率。结果发现：在５‰～４０‰范围内，该氵蚤个体耗氧率受盐度的影响不显著，但表现出在１０‰时略高，５‰时较低，２０‰～４０‰内相近的特点；各盐度下随体长增加，氵蚤耗氧率明显升高，两者间呈显著正相关；在试验盐度内，幼氵蚤的个体耗氧率和比耗氧率分别为４．２～７．１μｇ／（个·ｄ）和４０．８～８１．４μｇ／（ｍｇ·ｄ）；成氵蚤分别为５．９～１４．０μｇ／（个·ｄ）和４０．４～８０．６μｇ／（ｍｇ·ｄ）。根据试验结果并结合以往工作，认为１０‰是蒙古裸腹氵蚤代谢最旺盛的盐度。