基于LST_LAI特征空间的农田干旱监测研究

农田干旱具有范围广且对农业生产影响巨大的特点,对农田干旱的遥感实时动态监测是目前公认的难题。利用MODIS的地表温度(LST)产品和叶面积指数(LAI)产品,构建LST-LAI光谱特征空间,提出温度—叶面积干旱指数(temperature LAI drought index,TLDI)监测农田水分含量,并利用宁夏实测的0～10 cm平均土壤含水量验证该指数的精度,结果表明：它们之间具有良好的相关性,R2的变化范围为0.43～0.86。与TVDI相比,TLDI弥补了作物封垄后TVDI因归一化植被指数(NDVI)饱和对农田水分监测精度降低的缺陷。此外,利用MODIS数据产品LST和LAI进行农田干旱监测,避免了使用MODIS原始数据的繁杂处理过程,初步为MODIS数据产品在农田干旱监测业务化运行探索出一条技术流程。     

洪涝胁迫的水稻叶面积指数变化及其光谱响应研究

通过水稻淹水实验模拟洪涝胁迫状态,分析不同生育期、不同洪涝胁迫强度下的水稻叶面积指数变化及其冠层高光谱响应规律,建立洪涝胁迫下水稻叶面积指数(LAI)的估测模型。结果表明,分蘖期、拔节期、抽穗期水稻LAI均随淹水深度的增加而降低;水稻冠层680~760 nm光谱的一阶微分具有“双峰”现象,主峰位于724~737 nm,701和718 nm有次峰出现,并随淹水深度的增加出现“三峰”;冠层红边位置在各个生育期出现“蓝移”,红边幅值、红边面积在分蘖期、拔节期、灌浆期均呈现“蓝移”,在抽穗期出现“红移”;生育前期水稻LAI与光谱特征参量存在显著相关,生育后期相关性不显著;最后以D_λ737/D_λ718光谱参量建立了水稻生育前期的LAI估测模型。表明在洪涝胁迫下,水稻LAI的变化幅度直接反映胁迫强度的大小,估测模型LAI=3.138(D_λ737/D_λ718)-0.806可用于估测洪涝胁迫不同强度下的水稻叶面积指数。     

近红外光谱法测定苜蓿中的叶含量

叶含量是一项对苜蓿的营养价值和家畜采食量、消化率都很重要的指标,目前常用的手工茎叶分离后测定叶含量的方法非常费时费力。利用近红外光谱分析技术(NIRS)对人工配制叶含量为15%～55%的41个苜蓿样品, 建立了苜蓿中叶含量的预测模型。用15,25, 35个定标样品分别建立的3个模型的RMSEP分别为1.02, 1.97, 0.51,RPD依次为5.50,2.85,25.93,外部验证的决定系数r2为0.978 9,0.984 4,0.998 9。结果表明,15个定标样品已经能够建立准确测定苜蓿叶含量的近红外预测模型,且模型的准确性随着数量增加而升高。     

Hereditary tree growth and Lévy forests

We introduce the notion of a hereditary property for rooted real trees and we also consider reduction of trees by a given hereditary property. Leaf-length erasure, also called trimming, is included as a special case of hereditary reduction. We only consider the metric structure of trees, and our framework is the space $\mathbb{T}$ of pointed isometry classes of locally compact rooted real trees equipped with the Gromov–Hausdorff distance. We discuss general tightness criteria in $\mathbb{T}$ and limit theorems for growing families of trees. We apply these results to Galton–Watson trees with exponentially distributed edge lengths. This class is preserved by hereditary reduction. Then we consider families of such Galton–Watson trees that are consistent under hereditary reduction and that we call growth processes. We prove that the associated families of offspring distributions are completely characterised by the branching mechanism of a continuous-state branching process. We also prove that such growth processes converge to Lévy forests. As a by-product of this convergence, we obtain a characterisation of the laws of Lévy forests in terms of leaf-length erasure and we obtain invariance principles for discrete Galton–Watson trees, including the super-critical cases.     

胶束增敏分光光度法测定大豆根茎叶中的镧

首次了二溴基偶氮比例中表面活性剂曲通Ｘ－１００和β环糊精存在下与Ｌａ（Ⅲ）的显色反应。在强酸介质中与Ｌａ（Ⅲ）形成稳定的配合物,最大吸收波长在６３８ｎｍ处,配合物的表观魔鬼洋吸光系数为１．５０×１０＾５Ｌ·ｍｏｌ＾－１·ｃｍ＾－１,比献「１」中的灵敏度高２７％。该法已用于大 奶、茎、叶中镧的测定。     

近红外光谱技术在天然草地植被管理中的应用

植被是监测草地健康和生产力的主要依据,其变化是草地生态系统退化和恢复状况的最直接体现。及时掌握草地植被的变化信息是防止草地退化、实现草地生态系统可持续发展的首要条件。近红外光谱技术以其简便、快捷等优越性广泛应用于不同领域,在草地资源管理中有巨大的应用潜力和前景。文章介绍了近红外光谱技术的原理、特点及其在草地植被物种组成、草地植物茎叶比、凋落物及牧草品质测定等方面的应用特点,综合阐述了近红外光谱技术在草地植被管理中的应用现状,并对其应用前景进行了展望。     

Ultramicroscopy reveals that senescence induces in-situ and vacuolar degradation of plastoglobules in aging watermelon leaves

The dynamics of plastoglobules in chloroplasts in aging watermelon leaves were examined by means of transmission electron microscopy, with the aim to understand the intracellular sites for the degradation of plastoglobules in response to leaf senescence. Plastoglobules in chloroplasts in aging leaves with 40% loss of chlorophyll increased drastically in number and size in comparison with young and mature leaves. As senescence advanced, plastoglobules underwent degradation within chloroplasts, or were secreted outside chloroplasts. There were two distinct types of secretion. One type was that chloroplasts protruded to form plastoglobule-containing vesicles and, as the vesicles were detached from chloroplasts, plastoglobules were carried outside chloroplasts. The other type was that plastoglobules squeezed out through the chloroplast envelope into cytoplasm. Lipid droplets were present in the vacuole and underwent degradation therein. Lipid droplets in the vacuole shared similar ultramicroscopic appearance with plastoglobules in chloroplasts, indicating that plastoglobules were engulfed and degraded by the vacuole after they were secreted outside chloroplasts. These results suggested that senescence induces both in-situ and vacuolar degradation of plastoglobules in aging watermelon leaves.     

Anticomplement and antitussive activities of major compound extracted from Chimonanthus nitens Oliv. leaf

Chimonanthus nitens Oliv. leaf (CNOL), as a traditional Chinese medicine, has been widely used for the treatment of influenza and colds over a long history. However, the mechanism of colds related to the effects of CNOL have been little studied. In this study, the anticomplement and antitussive activities of different polarity extracts of CNOL were evaluated. Ethyl acetate extract (EAE) among different extracts not only significantly decreased cough times by 21–58% (P < 0.01), but also had anticomplement effects demonstrated by the CH₅₀ values of 0.100 mg/ml. A total of 28 constituents (10 coumarins, 13 flavonoids and five phenolics) were identified in EAE based on the ultra-high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry technique. Eight compounds in EAE were evaluated by an ammonia-induced cough model to reveal the antitussive mechanisms and classical anticomplement pathway. The results indicated that the antitussive effects of scopoletin, kaempferol-3-O-rutinoside and kaempferol may depend on central mechanisms and that flavonoids such as compounds of kaempferol-3-O-rutinoside and kaempferol have better anticomplementary activity than coumarins like compounds of scopolin, scopoletin and isofraxidin. Taken together, kaempferol-3-O-rutinoside and kaempferol could be important chemical markers in the present study that might be used to evaluate the quality and biological activity of CNOL.     

Strictly chordal graphs are leaf powers

A fundamental problem in computational biology is the phylogeny reconstruction for a set of specific organisms. One of the graph theoretical approaches is to construct a similarity graph on the set of organisms where adjacency indicates evolutionary closeness, and then to reconstruct a phylogeny by computing a tree interconnecting the organisms such that leaves in the tree are labeled by the organisms and every organism appears as a leaf in the tree. The similarity graph is simple and undirected. For any pair of adjacent organisms in the similarity graph, their distance in the output tree, which is measured by the number of edges on the path connecting them, must be less than some pre-specified bound. This is known as the problem of recognizing leaf powers and computing leaf roots. Graphs that are leaf powers are known to be chordal. It is shown in this paper that all strictly chordal graphs are leaf powers and a linear time algorithm is presented to compute a leaf root for any given strictly chordal graph. An intermediate root-and-power problem, the Steiner root problem, is also examined.