硅对铬胁迫下小白菜生理指标的影响

通过土培试验,研究了施硅对铬胁迫下小白菜(Brassica parichinensis)产量、叶绿素含量以及过氧化氢酶(CAT)和过氧化物酶(POD)的影响.结果表明:当土壤中未加铬(cr6 )时,随着硅浓度的增加,小白菜产量逐渐增加,叶绿素含量减少;在不同铬(Cr6 )处理的土壤中,施加0.5 g·kg-1 Na2SiO3可显著增加小白菜产量(P＜0.05);1.0 g·kg-1的硅可显著降低铬对小白菜叶片CAT和POD的活性,抑制铬对小白菜的毒害作用;硅浓度继续增加,其抑制效果开始降低.     

盐胁迫下构树幼苗各器官中K+ 、Ca2+ 、Na+ 和Cl-含量分布及吸收特征

将当年生构树幼苗置于含有不同浓度(0.4、1、2、3、4 g·kg-1)NaCl的土壤中,研究其生物量积累、叶片细胞质膜透性和K+、Ca2+、Na+、Cl-等离子的吸收、分布及运输,并观察盐害症状.结果表明:构树幼苗的叶片质膜透性随着NaCl浓度的增加和胁迫时间的延长而升高,根冠比随NaCl浓度的升高而增加,大于3 g·kg-1的土壤盐胁迫对构树叶片的质膜透性及植株的生物量积累影响显著.构树幼苗各器官中Na+和Cl-含量随土壤NaCl浓度升高而显著增加,K+和Ca2+则随之降低,叶片各离子含量均明显高于根和茎.说明盐胁迫影响根系对K+和Ca2+的吸收,并抑制了它们向地上部分的选择性运输,使叶和茎的K+和Ca2+含量下降.构树通过吸收积累Na+和Cl-抵御土壤盐分带来的渗透胁迫,但过量的Na+和Cl-积累会造成单盐毒害.作为抗盐性较高的非盐生植物,构树地上部分的拒盐作用不显著.     

生物炭调控盐胁迫下水稻幼苗耐盐性能

土壤盐渍化降低土壤生产力。探索生物炭对盐胁迫下水稻幼苗耐盐性能的影响,对调控盐渍区水稻生产潜力具有重要意义。本研究通过生物炭介入盐胁迫稻田土壤的盆栽试验,调查了生物炭对盐胁迫下土壤环境和水稻幼苗耐盐性能的影响。盐胁迫设置4个水平,分别为0 g NaCl·kg^-1土(S0),1 g NaCl·kg^-1土(S1),2 g NaCl·kg^-1土(S2),3 g NaCl·kg^-1土(S3)。生物炭设置2个水平,分别为0 g生物炭·kg^-1土(C0),3 g生物炭·kg^-1土(C1)。结果表明:生物炭介入盐胁迫土壤,显著提高了水稻幼苗地上部干物重,有效改善了水稻幼苗农艺性状,显著提高了水稻幼苗茎秆中全钾含量,显著提高水稻幼苗钾钠比79.61%,提高了水稻幼苗耐盐性。生物炭介入也对水稻幼苗抗氧化性能有改善作用,显著降低了水稻幼苗中丙二醛含量,平均显著降低14.25%,抑制膜脂过氧化作用,提高抗氧化能力,减轻盐胁迫对水稻幼苗的伤害。水稻幼苗收获后土壤中水溶性氯离子和水溶性钠离子含量在生物炭介入条件下分别显著降低9.13%、17.77%。因此,添加适量生物炭能有效降低土壤水溶性盐含量,改善土壤盐胁迫环境,提升水稻对盐渍土壤的适应能力。     

山东寿光不同利用方式下农田土壤有机质和氮磷钾状况及其变化

通过对山东省寿光市不同利用方式下土壤相关性质的比较,探讨了农田土壤有机质和氮磷钾含量状况,并分析了设施菜地种植年限与有机质、全量氮磷含量的相互关系.研究结果表明:山东寿光农田土壤有机质和全量氮磷含量与第二次土壤普查时比较均有较大幅度增加,其中以设施菜地增加幅度最大,分别达120%、160%和364%,但全钾含量的增加幅度很小、仅为17.5%;不同利用方式比较,设施菜地土壤有机质、全氮、全磷含量均明显高于露天菜地、小麦/玉米地及棉花地,而全钾含量则低于小麦/玉米地和棉花地;从养分含量的分级结果看,设施菜地有机质、全量氮磷钾含量主要分布于>20g · kg-1、>1.2g · kg-1、>1.0 g · kg-1、20～25g · kg-1的级别中;设施菜地种植年限与土壤有机质、全量氮磷含量变化间有显著相关性,且均可用Y=a+bX+cX2的形式来表示,即随种植年限增加,有机质与氮磷含量首先呈逐步增加的趋势,并分别在第9.6年、8.9年和11.4年时达到最高值,之后则有随种植年限延长而下降的趋势.     

在蚯蚓影响下土壤Pb、Cd有效态的变化及小白菜对Pb、Cd的富集转移作用

研究了在蚯蚓影响下Pb、Cd添加量不同(Pb:500～1 700 μg·g-1;Cd:1～30 μg·g-1)的土壤中Pb和Cd有效态及其含量的变化以及小白菜(Brassica chinensis L. )对土壤中Pb和Cd的富集和转移作用.结果显示,在蚯蚓的影响下,Pb添加量为500～1 400 μg·g-1的土壤中酸提取态和可还原态Pb含量显著提高,有效态Pb总含量也随土壤中Pb添加量的提高逐渐增加;Cd添加量为5～20 μg·g-1的土壤中酸提取态Cd含量显著提高,有效态Cd总含量也随土壤中Cd添加量的提高而逐渐增加;当土壤中Pb和Cd添加量分别达到1 700和30 μg·g-1时,蚯蚓对Pb和Cd基本无活化作用.在蚯蚓的影响下,小白菜地上部分Pb含量显著提高,对Pb的转移系数也均高于各自的对照,地上部分和地下部分对Pb的富集系数分别为0.037～0.061和0.401～0.628.在蚯蚓影响下,在Cd添加量较低(1～5 μg·g-1)的土壤中小白菜地上部分和地下部分的Cd含量以及对Cd的富集系数均高于各自的对照;而在Cd添加量较高(10～30 μg·g-1)的土壤中小白菜地上部分和地下部分的Cd含量以及对Cd的富集系数均低于各自的对照,并随土壤中Cd添加量的提高逐渐降低;小白菜地上部分和地下部分对Cd的富集系数分别为1.196～11.516和1.744～20.425;各处理组小白菜对Cd的转移系数与各自的对照差异不显著.研究结果显示,蚯蚓主要对土壤中酸提取态和可还原态Pb以及酸提取态Cd有活化作用,并且可促进Pb由小白菜地下部分向地上部分的转移,但对Cd的转移无明显促进作用;此外,小白菜对Pb的富集作用不明显,但对Cd有一定的富集能力,这种能力的大小与土壤Cd含量有关.     

盐胁迫对Bt棉棉蕾杀虫蛋白表达的影响

为探讨土壤盐分对转Bt基因抗虫棉棉蕾抗虫性的影响程度,采用盆栽试验,以2个Bt棉品种‘新棉33B’(盐敏感)和‘中07’(耐盐)为试验材料,设置5个土壤盐分水平(0、0.15%、0.30%、0.45%和0.60%), 研究盐分对蕾期Bt棉棉蕾中杀虫蛋白含量、Bt基因相对表达量及氮代谢相关酶和物质代谢的影响.结果表明: 棉蕾中Bt杀虫蛋白含量随土壤盐分的升高而降低,与对照相比(0%),2个不同类型棉花品种在土壤盐分0.30%及以上时,棉蕾中杀虫蛋白含量显著下降,且随土壤盐分水平的升高,Bt 杀虫蛋白含量下降幅度增大.土壤盐分胁迫提高了棉蕾中Bt基因的相对表达量.在相同土壤盐分水平下,盐敏感品种棉蕾中Bt杀虫蛋白含量受土壤盐分影响较大.杀虫蛋白表达量下降幅度大的品种,其可溶性蛋白含量、谷氨酸丙酮酸转氨酶(GPT)和谷氨酸草酰乙酸转氨酶(GOT)活性下降幅度较大,游离氨基酸含量、蛋白酶和肽酶活性上升幅度也较高.说明土壤盐分胁迫下,Bt棉棉蕾蛋白质合成能力下降,分解能力增强,可能是导致杀虫蛋白表达量下降的主要原因.     

山东寿光不同种植年限设施土壤的酸化与盐渍化

以山东寿光不同种植年限设施菜地为对象,研究并分析了土壤的酸化与盐渍化状况,结果表明:设施菜地土壤pH值平均为6.86,全盐含量为2.47g.kg-1,与露天菜地、自然土相比有较明显的酸化与盐渍化现象;设施菜地在连续种植0-12.7a间,土壤pH值随种植年限增加而降低,12.7a后则出现随种植年限增加而升高的现象,土壤全盐含量则表现出与pH值相反的变化趋势,其发生变化的转折年限约为8.4a;设施土壤中的Na+,Mg2+,Cl-,SO24-含量随种植年限的变化均表现出与土壤全盐量相同的趋势,且与种植年限的相关性均达到显著水平,这4种离子含量的变化可能是导致土壤全盐量随种植年限变化的重要原因;从土壤盐分离子组成来看,设施菜地土壤主要以SO42-、Cl-、Ca2+为主,分别占全盐量的62.4%、10.6%、9.3%,设施菜地中SO24-、Cl-、Mg2+、Na+含量与全盐量均呈极显著相关,其中相关性程度最大的为SO24-(r=0.9291)和Mg2+(r=0.7224)。设施菜地中SO24-含量与pH值变化存在极显著相关(r=-0.5508),其大量累积可能是造成调查区域设施土壤酸化的重要原因。     

四季竹耐盐能力的季节性差异

以四季竹2 a生竹苗为材料,通过盆栽试验设置土壤不同NaCl含量模拟盐胁迫环境,研究其在非生理活跃期的冬季(11-12月份)和生理活跃期的夏季(5-6月份)盐胁迫下的生理响应和叶片脱落情况,以了解四季竹耐盐能力的季节性差异。结果表明,在低土壤NaCl盐分(1‰-2‰)条件下,相同浓度处理45 d的竹苗叶片脱落率和各项生理指标较对照变化在冬季和夏季间差异不大,说明在低盐分条件下四季竹耐盐能力季节性差异不明显。在高土壤NaCl盐分(3‰-5‰)条件下,相同浓度处理45 d的叶片中除可溶性蛋白含量较对照升降幅度冬夏两季基本一致外,叶片脱落率、离子渗漏率、SOD活性、POD活性、脯氨酸含量和叶绿素含量分别较对照增加或降低的幅度冬季均显著小于夏季,并且随土壤NaCl浓度的提高冬夏两季的差异逐渐加大,而丙二醛含量和叶绿素a／叶绿素 b变化规律在夏冬两季间完全相反,说明在高土壤盐分(3‰-5‰)条件下相同浓度、相同时间处理的四季竹在夏季的受伤害程度显著大于冬季,即高盐条件下四季竹在生理活跃期的夏季的耐盐能力较非生理活跃期的冬季弱。土壤盐分和环境温度对四季竹生长具有较强的交互作用。     

北京松山自然保护区不同母质油松林土壤氮、磷、钾含量垂直分布

以北京市松山自然保护区同海拔油松林下两种母质(花岗岩和石灰岩)上发育的土壤为对象,研究了土壤的全氮、有效磷、速效钾含量在剖面的垂直变化.结果表明:花岗岩母质发育的土壤0～20cm土层的全氮、有效磷和速效钾含量分别为1.61～2.35g·kg-1、5.84～10.74mg·kg-1和39.33～93.66mg·kg-1,石灰岩母质发育的土壤分别为1.69～2.36g·kg-1、4.45～8.57mg·kg-1和60.66～124.00mg·kg-1.两种母质发育的土壤0～10cm土层的全氮、有效磷和速效钾含量均最大,且与各土层之间差异均极显著,并随土层深度的增加而下降,说明土壤全氮、有效磷和速效钾含量的分布有很强的表聚性,而且石灰岩母质发育的土壤的表聚性更强.对同土层土壤进行配对t检验,全氮含量在各土层之间无显著性差异,有效磷含量在0～10cm土层差异极显著,速效钾含量在10～20cm土层之间差异显著.     

NaCl胁迫下苯丙烯酸在黄瓜幼苗-土壤系统内的积累

采用盆栽试验,以耐盐黄瓜品种‘津绿5号’和盐敏感品种‘津优1号’为试材,研究了NaCl(585mg·kg-1土)胁迫下不同浓度苯丙烯酸对黄瓜幼苗-土壤系统内苯丙烯酸积累的影响.结果表明:苯丙烯酸施用浓度是影响土壤和黄瓜植株中苯丙烯酸含量的主要因子;除最高浓度(200 mg·kg-1土)外,其他处理的黄瓜植株苯丙烯酸含量均随处理浓度的增加而增加.盐分胁迫使苯丙烯酸的毒性作用增强,在中低浓度处理下,黄瓜植株中苯丙烯酸含量升高;在高浓度处理下,黄瓜幼苗生长量下降并导致植株中苯丙烯酸含量降低;‘津绿5号’在最高浓度(200 mg·kg-1土)处理时苯丙烯酸含量下降,而‘津优1号’从100 mg·kg-1土浓度就开始下降,反映出两个黄瓜品种的耐盐性差异.在黄瓜植株各部位中,苯丙烯酸主要在叶片中积累;而在黄瓜植株-土壤系统内,苯丙烯酸主要在土壤中积累.     

施加改良剂对重度盐碱地土壤盐碱动态及草本植物生长的影响

为了探索内陆重度盐碱地的改良新方法,实验通过聚合有机酸(聚马来酸酐和聚丙烯酸)作为降盐碱剂,采用阻盐碱层、表土成膜剂以及土壤孔隙改善剂相结合的方法,对大庆市典型内陆盐碱土进行了改良实验,并在改良后的土壤及对照样地上种植不同植物--白菜、萝卜、菠菜、豚草和长春花,评价改良效果.结果发现:(1)通过施加降盐碱剂、阻盐碱剂及土壤孔隙剂,土壤的pH值和含盐量均有明显降低,下降幅度分别为pH:0.8～1.2、含盐量:0.2%～0.5%,而且表层改良效果优于深层;(2)在上述改良基础上施用表土成膜剂,使得土壤深层与表层盐碱运动减慢,即表层盐碱更低而深层更高,有利于保持表层适宜作物生长的条件;(3)2种聚合有机物比较来看,聚马来酸酐的改良效果好于聚丙烯酸;(4)从5种植物的生长状况来看,施用上述改良剂后较对照能够明显提高作物成活以及生长,特别是改良早期5种植物均呈现明显的生长趋势,而在后期存在生长力下降的趋势,因此,在大面积改良过程中需要考虑连续多次施加降盐碱剂以增强效果.     

Increasing the okra salt threshold value with biochar amendments

Soil salinity is a severe worldwide environmental problem that adversely affects soil properties and the crop growth such as okra. We hypothesized that biochar soil amendments could increase the okra salt threshold, alleviate salt stress and improve soil productivity. In this study, a pot experiment was conducted to investigate whether biochar could ameliorate the effects of salinity on okra plants. Three biochar amendment (BA) soil applications (0%, 5% and 10% by mass of soil) were considered for seven irrigation water salinity levels (0.75, 1.0, 2.0, 4.0, 5.0, 6.0 and 7.0?dS?m^?1) in a randomized block design with three replications. The Maas and Hoffman salt tolerance model was used to evaluate the effects of BA on okra plant growth parameters (e.g. yield, biomass) and water use efficiency for each salinity treatment. The results showed that increasing the soil salinity levels caused significant decreases in plant yields and yield components. However, biochar application rates of 5% and 10% increased the okra threshold by 19.7% and 81.2%, respectively, compared to the control (0%). The 10% biochar application rate also resulted in the greatest okra plant growth and increased yield, indicating that the effects of salt stress were ameliorated; moreover, the soil bulk density was decreased, and the water content was increased. Hence, biochar soil amendments could be considered as an important agronomic practice that could potentially overcome the adverse effects of salt stress.     

The potential of soil amendment with insect exuviae and frass to control the cabbage root fly

Reliable options to control the cabbage root fly, Delia radicum L., are lacking in many countries as restrictions on insecticide use have tightened due to environmental concerns. Although microbial control agents are often considered as a sustainable alternative, their application in agriculture is constrained by inconsistent efficacy owing to low field persistence. To stimulate naturally occurring beneficial microbes, soil amendment with the residual streams of insect production has been suggested as an alternative to synthetic fertilization and a new approach to microbial crop protection. In a set of greenhouse experiments, exuviae and frass of black soldier fly larvae, Hermetia illucens L., house crickets, Acheta domesticus L. and exuviae of mealworms, Tenebrio molitor L., were added to soil from an organically managed field. Exuviae and frass treatments were compared to treatments with synthetic fertilizer. Brussels sprouts, Brassica oleracea L., plants were grown in amended soil for 5 weeks before being infested with cabbage root fly larvae. Insect and plant performance were assessed by recording cabbage root fly survival, biomass and eclosion time and seed germination and plant biomass, respectively. Whereas soil amendment with black soldier fly frass or exuviae reduced cabbage root fly survival and biomass, respectively, amendment with house cricket or mealworm residual streams did not negatively affect root fly performance. Furthermore, seed germination was reduced in soil amended with house cricket exuviae, while amendment with either residual stream derived from black soldier fly larvae or house crickets resulted in lower plant shoot biomass compared with the synthetic fertilizer treatment. Amending soil with black soldier fly residual streams could become a novel and low-cost tool to be integrated in cabbage root fly management programmes, especially where methods currently available are insufficient. Therefore, the mechanisms underlying the effects of insect-derived soil amendments described here should be the focus of future research.     

添加玉米和水稻秸秆对淹水土壤pH、二氧化碳及交换态铵的影响

通过温室土壤培养试验，研究了不同添加量玉米和水稻秸秆对淹水土壤pH、CO₂及交换态铵的影响.结果表明：在接近中性的土壤中加入秸秆可使土壤pH值降低，4 g·kg^-1玉米和水稻秸秆处理的土壤pH值均与对照差异显著（P＜0.05），而1 g·kg^-1玉米和水稻秸秆处理与对照差异不显著（P＞0.05）.土壤溶液中的CO₂含量随秸秆添加量的增加而增大，1 g·kg^-1玉米和水稻秸秆处理的土壤溶液CO₂含量最大值分别为35.9％和31.9％（v/v），与对照（25.8％）差异达显著水平（P＜0.05），但两者间差异不显著（P＞0.05）；4 g·kg^-1玉米和水稻秸秆处理的土壤溶液CO₂含量最大值分别为54.2％和41.8％（v/v），与对照差异极显著（P＜0.01），两者间差异也达显著水平（P＜0.05）.在不施氮肥的情况下，添加秸秆可降低土壤铵态氮浓度，且铵态氮浓度随秸秆添加量的增加而降低，不同添加量处理间差异显著（P＜0.05）；在施入氮肥的情况下，1 g·kg^-1玉米和水稻秸秆处理提高了土壤铵态氮浓度，而4 g·kg^-1玉米和水稻秸秆处理降低了土壤铵态氮浓度.无论是否施入氮肥，玉米和水稻秸秆处理的土壤铵态氮浓度差异不显著（P＞0.05）.     

Effect of a rock dust amendment on disease severity of tomato bacterial wilt

Nutrients are important for growth and development of plants and microbes, and they are also important factors in plant disease control. The objective of this study was to evaluate the effect of a rock dust used as a fertilizer in maintaining health of soil and tomato plants under greenhouse conditions. Four treatments—including M (commercial organic fertilizer), A (rock dust soil amendment), M + A (commercial organic fertilizer + rock dust soil amendment) and CK (blank control)—were examined for their effect on soil properties, soil enzymatic activity, plant growth and control efficacy against tomato bacterial wilt. Treatments A and M + A were significantly better than other treatments in changing soil pH, increasing it from acidic (pH 5.13) to nearly neutral (pH 6.81 and 6.70, respectively). Enzymatic activities in soil were notably influenced by the different treatments—particularly treatment M + A, which increased the activities of alkaline phosphatase, urease, catalase and sucrase to a greater extent in soil. There was no significant difference (P < 0.05) in the effects of treatments A and M + A on tomato plant height, stem diameter and biomass. The effect of the four treatments on the chlorophyll content and photosynthetic rate (in decreasing order) were M + A, A, M and CK. The replicate greenhouse experiments showed that the control efficacies of treatments M + A, A, and M against bacterial wilt were respectively 89.99, 81.11 and 8.89 % in first experiment and with the efficacies of 84.55, 74.36, and 13.49 % in the replicate; indicating that rock dust played a key role in the plant–soil interaction. The raised soil pH and Ca content were the key factors for the rock dust amendment controlling bacterial wilt under greenhouse conditions.     

施用泥炭对风沙土改良及蔬菜生长的影响

通过盆栽试验比较了施用不同剂量的泥炭(0％、2％、5％、8％及10％)对风沙土改良的效果和对白菜生长及产量的影响。结果表明,泥炭能增强风沙土的持水能力,降低土壤的pH值,增加土壤中有机质、全氮、速效氮和速效磷等的含量;白菜根系长度、生物量、高生长和地上部分的生物量均有增加,其中8％泥炭处理为最佳,其根系长度、根鲜重、干重、高生长、地上部分鲜重、干重依次比对照增加71％、402％、464％、107％、847％和1001％;同时施用泥炭还有利于提高白菜干物质的积累及其品质。     

土壤盐度对加拿利海枣幼苗生长与生理指标的影响

将加拿利海枣(Phoenix canariensis Hort. ex Chab.)幼苗培养在不同盐度(1.2~14.5)的土壤中,探讨土壤含盐量对其生长及生理指标的影响。结果表明:随基质盐度的提高,幼苗新生叶片数降低且叶片死亡数增加。随基质盐度的提高,叶绿素含量增加,叶绿素a/b在低盐度时增加而当盐度超过5.1时下降。土壤盐度在1.2~5.1时,MDA含量约为4.30 μmol g^-1,以后随土壤盐度的升高而升高。SOD活性在低盐时升高,土壤盐度超过10.8时,SOD活性迅速下降。盐胁迫下叶片Na⁺和Cl^-含量升高,K⁺、Ca²⁺、Mg²⁺含量及K⁺/Na⁺下降。盐胁迫导致加拿利海枣生长下降的主要原因是叶片有效光合面积减少,离子平衡破坏。这些表明加拿利海枣具有很高的耐盐能力,其幼苗在土壤盐度5.1时生长正常,当土壤盐度为10.8时才开始出现受害症状,适宜在滨海地区推广应用。     

Effects of Sewage Sludge on the Growth of Potted Salt Marsh Plants Exposed to Natural Tidal Inundation

Abstract A growth experiment with native plants in pots exposed to natural environmental conditions evaluates the use of sewage sludge as a soil amendment in restoration of a southern California salt marsh. Sludge containing desirable organic matter but also undesirable heavy metal contaminants was mixed with a readily available matrix soil to reduce metal concentrations to levels below legal limits for land applications of sludge. Soil nutrient analysis revealed expected increases in total nitrogen and total phosphorus content with increasing sludge concentration. Soil metals analysis, however, revealed decreases in metal content with increased sludge concentration, a trend evidently caused by higher than expected metal content in the matrix soil. Five artificial soil mixtures ranging from 0 to 70% sludge were accompanied by natural wetland soil controls. Pots containing these soils were placed into a natural salt marsh. The pots were then planted with two native salt marsh plant species, Salicornia virginica and Frankenia grandifolia. Aboveground biomass was harvested after 12 months. Plant growth displayed no obvious change with increasing sludge concentration. Over the concentration ranges used, increased nutrient content did not stimulate plant growth and increased metal content did not inhibit plant growth. Plants grew better in natural wetland soil than in artificial soil mixtures, a trend probably caused by the substantially finer texture and higher organic content of natural soil. All sludge treatments differed more from the natural soil than from each other, implying that within the ranges examined, soil texture and organic content exerted more influence on plant growth than did metal or nutrient concentration. These results suggest that incorporating this sewage sludge in the soil of the restored salt marsh will neither benefit nor harm the plants that will live there and that greatest plant growth will be achieved by mixing the sludge with a fine‐grained matrix soil.     

杨柴对高CO2浓度和土壤干旱胁迫的响应

毛乌素优势植物杨柴 (HedysarummongolicumTurcz.)对高CO2 浓度和土壤干旱胁迫响应的研究结果表明 :干旱胁迫可使杨柴根系伸长 ,根生物量、地径、主茎高和茎生物量下降 ;高CO2 浓度使杨柴根和茎生物量明显增加 ,CO2 的“施肥效应”显著 ,干旱使CO2 的“施肥效应”减弱。同时 ,土壤干旱胁迫使杨柴的根 /冠比增加 ,说明在土壤干旱胁迫情况下根的生长比地上部分 (茎 )的生长更活跃 ,有利于提高杨柴在干旱沙漠地区的固沙作用 ;CO2 浓度升高和土壤干旱胁迫均使杨柴叶片的水势下降 ,叶片水势的下降使叶片细胞对水分的束缚力增强 ,从而减少植物蒸腾耗水 ,有利于提高水资源的利用效率