石榴树吸水根根系空间分布特征

笔者对太行山低山丘陵区石榴树吸水根根系空间分布特征进行研究 ,结果表明 :在垂直方向上 ,石榴吸水根根量主要集中于 0～ 80cm土层内 ,约占总量 91.32 % ,80cm土层以下仅约为总量的 8.6 8%左右 ,根长密度随土层深度的变化 ,呈负指数函数分布 ;在水平方向上 ,主要分布为距果树行带 0～ 10 0cm范围内 ,石榴吸水根根量约占总量的 76 .0 7% ,而距果树行带 10 0～ 2 5 0cm时其只占总量的 2 3.93%。

果农复合系统中果树根系空间分布特征

本文对太行山低山丘陵区苹果 小麦复合系统果树吸水根根系空间分布特征进行研究 ,以期为苹麦复合系统苹果根系吸水运移模型的建立及水分生态特征的分析提供基础资料。结果表明 :垂直方向上 ,苹果吸水根根量主要集中 0～ 80cm土层内 ,约占总量 94 33% ,且 0～ 4 0cm所占比例较大 ,达 6 3 76 % ,80cm土层以下仅约为总量的 5 6 7%左右 ;在水平方向上 ,分布在林带区和作物区内各占 39 71%和 6 0 2 9% ,其中作物区内的根量主要集中在 4 0～ 12 0cm带距范围内 ,约占作物区内的 74 7% ;吸水根根长密度 (RD :cm·cm- 3)与距果树带距离 (X :cm)、土壤深度 (Z :cm)的关系方程式可表达为 :RD =- 6 6 17× 10 - 9Z4 +1 814 9× 10 - 6 Z3-1 75 2 6× 10 - 4Z2 +4 94 18× 10 - 3Z - 5 83× 10 - 7X2 +- 2 16× 10 - 5X +1 12 99ZX +0 0 6 35 9,复相关系数r =0 86 4 7。

畦灌条件下樱桃树根系的空间分布特征

在对北京市永乐店农业节水灌溉试验站内的樱桃树根系进行详细调查的基础上,该文对樱桃树根系在根区范围内的空间分布特征进行了分析。结果表明,定植12a樱桃树的根系分布在以树干为中心250cm半径范围内,最大垂直深度为100cm。根系干质量、体积、表面积及根长各主要参数的总体分布是从表层开始随着土层深度的增加逐渐减少,从树干开始沿半径方向随着离树干距离的增加逐渐减少。根系各主要参数在各土层深度的分布百分比与其相应的土层深度均存在良好的指数相关关系。按照相关系数进行评价,相关程度按表面积(R2=0.9342)、根长(R2=0.9261)、体积(R2=0.9136)及干质量(R2=0.9050)的顺序逐渐减小。各采样单元内直径小于2mm的吸水根比例在35%～100%(平均68%)范围内分布。吸水根主要分布在以树干为中心200cm半径范围内,垂直方向从树干下方的60cm开始,逐渐减少到距树干水平200cm处的20cm左右,在树干周围半径为50cm和80～160cm范围是两个分布密集区。

滴灌湿润比对成龄库尔勒香梨树根系分布的影响

在充分灌溉条件下采用3种滴灌湿润比（20%、40%、60%）,以漫灌为对照,研究库尔勒成龄香梨吸水根（根直径≤1 mm）在0－70 cm土层内分布的变化,探讨滴灌湿润比对根系分布的影响。结果表明,漫灌成龄库尔勒香梨树吸水根水平方向上在距树体1－2 m内从树行由内向外呈递增趋势;垂直方向上根系随深度呈递增趋势。滴灌对成龄库尔勒香梨树根系分布具有显著的影响：水平方向上吸水根有向滴灌湿润区集中的趋势,并且湿润体内的根系密度随滴灌湿润比增大而递增;非湿润体内,吸水根系数量减少,根系密度随滴灌湿润比增大呈递减趋势。垂直方向,滴灌湿润区吸水根有向20－40 cm土层集中的趋势,其中湿润比20%趋势最明显,湿润比60%次之,湿润比40%影响最小。成龄库尔勒香梨在由漫灌改为地表滴灌初期,滴灌湿润比采用40%较合适。研究结果对库尔勒成龄香梨滴灌系统的设计和管理具有一定的指导意义。

我国中亚热带人工林水热通量对干旱差异响应的模拟研究

季节性干旱现象在我国中亚热带地区时有发生,为了研究该区域大气-生态系统之间的相互作用关系及其碳水收支状况,2002年起在江西省千烟洲(26.7°N,115.1°E)人工林生态系统建立了通量观测塔。2003年7月该人工林生态系统遭遇了历史上少有的高温少雨天气,本研究应用基于生理生态学过程的EALCO(Ecological Assimilation of Land and Climate Observation)模型及2003和2004年通量观测数据对该生态系统的水热通量进行了模拟,同时分析了干旱胁迫对它们产生的影响。结果显示,模型能够很好的模拟该生态系统的能量通量的日变化,净辐射、显热和潜热通量模拟值与实测值相关系数的平方(R2)及标准差分别为0.99和8.05 W.m-2;0.81和41.02 W.m-2;0.90和31.49 W.m-2,模型可以解释87%的日蒸散量的变化。从模拟结果看,2003年7月下旬(发生较严重干旱胁迫)较2004年同期(干旱程度轻)相比,冠层及土壤水势下降约2倍,植物蒸腾的日变化形式改变,根系吸水滞后冠层蒸腾的时间缩短约半小时,冠层导度下降40%～60%。模拟与观测结果均表明,2003年7月下旬每天正午的波文比大都介于1～2.2,而2004年同期正午的波文比则介于0.2～0.6。EALCO模型通过Ball模型将植物碳水过程耦合在一起,从而可以很好的模拟植物的气孔行为,进而准确的模拟植物水热过程对干旱的响应。土壤水分匮乏对冠层导度的限制是2003年干旱期间冠层潜热通量模拟值下降的根本原因。

花椒杂草系统地下生物量的空间分配格局

农林复合系统中，地下生物量的分配格局是目的物种和间作作物竞争的结果，因而可以看作是模式物种选择及系统设计的依据。在花椒杂草系统模式更新改造中，为了达到间作作物选择和行间配置的合理性，采用壕沟法研究了系统地下生物量的空间分配现状。结果表明：（1）花椒杂草系统地下生物量总量248．57g·m^-2，杂草生物量占82％，花椒仅占18％；（2）该系统地下生物量总量和杂草生物量在水平空间上呈均匀分配，而在垂直空间上随土层加深呈负指数分配，其表达式分别是Y=1024．6exp^-0.5254x（R^2=0．9688，x为土层深度，cm）和Y=1187．2exp^-0.6889（R^2=0．9989，x为土层深度，cm）；花椒根量均匀分配于垂直空间，而在水平空间上呈负指数式分配，其表达式为Y=118．3exp^-0.3817x（R^2=0．8215，x为距树干距离）；（3）花椒吸水根生物量均匀分配于地下空间，杂草吸水根生物量的分配呈现出明显的分层现象，其吸水根总量的81．11％分配于0～15cm土层，而15cm以下土层仅占18．89％；（4）所研究的256个500cm^3的取样单元中，花椒和杂草吸水根的重合率50．4％，非重合率49．6％；然而在127个吸水根非重合单元中，花椒吸水根仅占29．1％，杂草吸水根却占了70．9％。文中根据花椒和杂草地下空间生物量的分配现状，讨论了四川盆地丘陵区退耕还林地花椒模式更新中间作物选择、行间配置和水肥管理应注意的问题．

Effects of Nitrate on the Growth of Lateral Root and Nitrogen Absorption in Rice

Lateral root is primary organ for plant to explore and utilize soil nutrient efficiently. The development of lateral roots (LR) is controlled by both genetic factors and nutrient status in environment. To investigate the effects of nitrate (NO3-) on rice lateral root growth and nitrogen (N) uptake efficiency under upland condition, three treatments, including root-split culture and whole plant culture in N sufficient and deficient conditions, were used in a vermiculite culture experiment. Root-split treatment showed that the growth of lateral roots was stimulated by localized nitrate supply. However, in whole plant culture, elongation of lateral roots was induced by NO3- deficiency. The effects of NO3- on rice lateral root growth were genotype-dependent. Similar N concentration, soluble sugar concentration and N content in shoot were observed in both root-split treatment and whole plant culture under NO3- sufficient condition, suggesting that the nitrogen requirement for rice normal growth could be satisfied with only half of roots supplied with NO3-. In the root-split treatment, N uptake was positively correlated with the average of lateral root length (ALRL) in NO3--supplied side, suggesting that the ALRL is important for rice root N uptake in the environment where the nitrogen nutrient is limiting factor. No significant correlation was observed between N uptake and ALRL in whole plant culture under N sufficient condition, which implies that the length of lateral roots may not be the main factor to determine tire rice root N uptake in nutrient-rich zone. Morphological and metabolic evidence in this study provided some prospects for genetic improvement of root system characters to improve the efficiency of nutrient absorption in rice.

A Preliminary Study on Models of Root Water Uptake Based on Root Weight

Water uptake by crop roots is influenced by many factors. In this study, on the basis of previous studies, root water uptake models were established with the root weight as a dependent variable from the perspective of root biomass changes according to the theory of soil water dynamics. The established models were verified and evaluated using two indicators： root-mean-square error （RMSE） and mean absolute percentage error （MAPE）. The results indicated that the annual variation range of root-mean-square error （RMSE） was 0.477-1.231, with an aver- age of 0.810; the annual variation range of mean absolute percentage error （MAPE） was 1.082%-4.052%, with an average of 2.520%, suggesting that the simulation accuracy basically met the requirements. The established numerical models of root water uptake and the compiled program exhibit high simulation accuracy, which can perfectly simulate soil water dynamics during the growth period of crops under nat- ural conditions.

Study on the Activity of Herbal Extract to Kill Root-knot Nematode of Cucumber Seedlings Stage

Present mature plants hydroponic technology was used,combined with some excellent characteristics,such as growth conditions was easy to control and process of root growth was easy to continuously observe,the nematicidal activity of 5 kinds of Chinese herbs extracts and the compound solution of Avermectin,with strong contact toxicity effect indoor,was systematically studied and investigated the affection on the root-knot nematode parasitized on the cucumber seeding stage. It is found that under the premise of no influence on root growth of cucumber,extracts from Picrorhiza scrophulariiflora and Punica granatum showed strong prevention and nematicidal activity,and had the similar efficacy of Avermectin; while the extracts from Cibotium barometz,Aucklandia lappa Decne and Fructus cnidii showed low nematicidal activity and various degrees inhibition effect on plant growth.

Growth and Phosphorus Uptake of Oat (Avena nuda L.) as Affected by Mineral Nitrogen Forms Supplied in Hydroponics and Soil Culture

Plants show different growth responses to N sources supplied with either NH4^＋ or NO3^-. The uptake of different N sources also affects the rhizosphere pH and therefore the bioavallability of soil phosphorus, particularly in alkaline soils. The plant growth, P uptake, and P availability in the rhizosphere of oat （Arena nuda L.） grown in hydroponics and in soil culture were investigated under supply with sole NH4^＋-N, sole NO3-N, or a combination. Sole NO^- -fed oat plants accumulated more biomass than sole NH4^＋ -fed ones. The highest biomass accumulation was observed when N was supplied with both NH^＋ -N and NO3^- -N. Growth of the plant root increased with the proportion of NO3^- in the cultural medium. Better root growth and higher root/shoot ratio were consistently observed in NO3^- fed plants. However, root vigor was the highest when N was supplied with NO3^- ＋NH4^＋. NH4^＋ supply reduced the rhizosphere pH but did not affect P uptake by plants grown in soils with CaHPO4 added as P source. No P deficiency was observed, and plant P concentrations were generally above 2 g kg^-1. P uptake was increased when N was supplied partly or solely as NO3^--N, similarly as biomass accumulation. The results suggested that oat was an NO3-preferring plant, and NO3^- -N was essential for plant growth and the maintenance of root absorption capacity. N supply with NH4^＋ -N did not improve P nutrition, which was most likely due to the absence of P deficiency.

植物水分生理中几个争议性问题的理论分析

本文对涉及王小菁教授主编的《植物生理学》(第8版)和慕课网关于植物水分生理的一些反馈意见进行了分析讨论。主要包括细胞衬质势的特性,衬质势被体相水溶液屏蔽,体相水含量低的细胞代谢不活跃的原因,无液泡细胞水势不应包含衬质势的原因,以及重力势造成的树冠细胞水势高反而缺水的问题并尝试提出了解释。同时也分析了"根压是根系的吸水动力"和根系"主动吸水"说法的误导性以及质外体途径在根部水分径向运输中比例很小的依据。