干旱胁迫下Si对甘蔗叶片相对水含量和抗氧化物酶活性的影响

【目的】研究干旱胁迫下不同Si（硅）水平对不同耐旱性甘蔗品种的抗氧化物酶活性的影响,为探索Si提高甘蔗抗旱性的生理基础提供依据。【方法】采用水培法,设置3个施Si浓度（0、0.2、1.7 mmol/L）,经不同PEG-6000胁迫时间（0、18、26、30、40 h）后,测定两个耐旱性甘蔗品种（ROC16和ROC22）甘蔗叶片的相对水含量（RWC）及超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）等保护酶活性。【结果】与对照处理（Si浓度0 mmol/L,PEC-6000胁迫时间0 h）相比,随着胁迫时间的延长不同浓度Si处理的叶片RWC持续下降,POD活性先降后升,CAT活性先升后降,SOD活性则表现为先降后升再降的抛物线式变化趋势。ROC22的抗氧化物酶活性均高于ROC16。【结论】施Si能提高甘蔗叶片RWC及SOD、POD和CAT的活性,且高Si浓度（1.7 mmol/L）比低Si浓度（0.2 mmol/L）效果好。     

水分胁迫对几种球根花卉生理指标的影响

通过PEG-6000根际模拟土壤水分胁迫的方法,对郁金香、风信子和欧洲水仙3种球根花卉的幼苗进行了胁迫处理,测定了其叶片相对含水量(RWC)、丙二醛(MDA)含量、叶片细胞膜相对透性及超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)3种保护酶活性的变化。结果表明,随着水分胁迫强度的增加,3种球根花卉各生理指标均有不同程度的变化,其中欧洲水仙叶片相对含水量的变化幅度小,MDA含量及细胞膜相对透性较低且变化幅度较小,3种酶的活性在水分胁迫结束时均高于处理前;郁金香和风信子叶片相对含水量的变化幅度较大,MDA含量及细胞膜相对透性较高且变化幅度较大,3种酶的活性在水分胁迫结束时均低于处理前。综合分析后得出,3种球根花卉中以欧洲水仙对干旱的适应力最强,初步认为其可作为干旱地区的庭院美化植物。     

干旱胁迫对毛白杨幼苗的生理影响

以毛白杨为试验材料,研究模拟干旱胁迫对其叶片相对含水量(RWC)、POD活性、脯氨酸含量的影响。结果表明:在模拟干旱胁迫条件下,叶片相对含水量较对照组均出现了不同程度的下降,其中模拟干旱胁迫最严重的试验组(PEG-6000浓度为30%)叶片相对含水量下降最为明显;叶片POD的活性较对照组均出现了上升,其中中度干旱胁迫(PEG-6000浓度为20%)的POD活性上升最为显著;脯氨酸的含量较对照组出现了不同程度的上升,并且模拟干旱胁迫越严重,脯氨酸含量上升的越显著。     

4种薰衣草属植物抗旱性综合评价

采用负水头供水控水装置控制盆土体积含水量,对轻度、中度和重度干旱胁迫0、10、20、30 d和40 d后4种薰衣草属植物叶片相对含水量(RWC)、丙二醛(MDA)、可溶性糖(SSC)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT) 5个抗旱生理指标的变化规律开展研究,旨在对其抗旱性进行综合评价。结果表明：随干旱胁迫强度和时间的增加,4种薰衣草的RWC均呈下降趋势,且轻度干旱胁迫的RWC显著高于中度和重度干旱胁迫（P＜0.05）,其中,干旱发生至重度胁迫时,普罗旺斯薰衣草的RWC最高,为56.56%,孟士德薰衣草仅为39.02%;而MDA和SSC则呈上升趋势,且随胁迫程度的增强而增加,其中,胁迫至40 d时,普罗旺斯薰衣草的MDA较0 d（CK）各处理水平增加幅度达118.67%, 而其SSC含量显著高于其它3种薰衣草。4种薰衣草的SOD和CAT活性呈先升后降的变化趋势,均于胁迫至20 d时达到最高值,且轻度干旱胁迫下的SOD和CAT活性高于中度和重度胁迫,其中,孟士德薰衣草的SOD和CAT活性最低。根据模糊数学隶属函数法综合评价分析得出,4种薰衣草抗旱性强弱依次为：狭叶薰衣草＞普罗旺斯薰衣草＞蝴蝶薰衣草＞孟士德薰衣草。     

Microwave l-band (1730 MHz) accurately estimates the relative water content in poplar leaves. A comparison with a near infrared water index (R1300/R1450)

In this study the estimation of reflectivity at 1730 MHz (l-band), measured with a microwave digital cordless telephony (DCT) patch antenna, is presented as an easy-to-handle and non-destructive new method to assess the relative water content (RWC) of poplar leaves and filter discs at different levels of dehydration. The accuracy of this new method has been contrasted with the R₁₃₀₀/R₁₄₅₀ index, determined by a portable near infrared (NIR) spectrometer. The close correlations found between RWC and the reflectivity at a frequency of 1730 MHz, both for filters and leaves, indicate that microwave determinations are rather independent of the physical properties of the material analysed. On the contrary, the differences found between poplar leaves and leaf filters in the relationships established between RWC and the R₁₃₀₀/R₁₄₅₀ index demonstrate a strong influence of the properties of the material in NIR reflectance measurements, specifically as they relate to changes in leaf thickness during dehydration. It should be noted that the amount of energy received by the leaf for the microwave technique (0.1 mW) was much lower than that received for the measuring of the R₁₃₀₀/R₁₄₅₀ index (2.5 W). Moreover, R-square coefficients were higher for microwaves than for the R₁₃₀₀/R₁₄₅₀ index. The use of a technologically simple, low cost and portable device, based on a microwave DCT patch antenna, could yield a solid support for the development of a commercial apparatus enabling the determination of plant water status under field conditions.     

Recommended prebioom copper spray has no beneficial effect on ‘delicious’ apple tree copper status or fruit typiness

Three field experiments were conducted to evaluate a new commercial recommendation to add small amounts of a Cu(OH)₂‐based fungicide, Kocide 101, to prebioom zinc (Zn) nutrient sprays in order to enhance ‘Delicious’ apple tree copper (Cu) status and improve fruit typiness. Treatments were (1) single prebioom spray of basic Zn sulfate in combination with varying rates of added Cu as Kocide; (2) single spray of Kocide alone at pink timing; and (3) single silver‐tip spray of Zn sulfate in combination with varying rates of Kocide or a more soluble Cu sulfate‐based product. The Cu sprays applied at silver‐tip had little or no effect on flower cluster Cu concentration at full bloom. Kocide applied at green‐tip and later increased flower cluster Cu. None of the Cu sprays influenced midsummer leaf Cu concentration. The Cu sprays had no beneficial effect on fruit mass or on any of five fruit typiness indices. The experimental results indicate that there are no detectable nutritional or fruit typiness benefits resulting from adding Kocide to Zn sprays at any prebioom timing, or from adding Cu sulfate to Zn sprays applied at silver‐tip bud stage.     

Influence of potassium humate on biochemical and agronomic attributes of bean plants grown on saline soil

To study the effect of soil application of potassium humate (KH) (0, 70 and 140 Kg ha^?1) on agronomic, biochemical attributes, and yield and its components on bean (Phaseolus vulgaris L.) cultivars ‘Bronco’ grown under two sites having different level of salinity (EC = 3.00 or 5.00 ± 0.20 dS m^?1). Two field trials were conducted at the Agriculture Test Station, Faculty of Agriculture, Fayoum University, in 2014 and 2015. The obtained results indicated that addition of KH increased all of the studied growth parameters, i.e. plant height, number of leaves, leaf area, stem diameter and canopy dry weight. Moreover addition of KH significantly increased membrane permeability measurements. KH significantly increased chemical composition related to salt tolerant either inorganic e.g. N, P, K, and decreased Na and Cl contents of leaves or organic components e.g. chlorophyll a + b, carotenoids, anthocyanin total phenolics, total flavonoids and proline. DPPH radical-scavenging activity and yield and its components were increased. The soil application of KH was found to be highly effective at improving the growth and yield of bean plants by alleviating the inhibitory effects of soil salinity stress.     

Response to drought and salt stress of lemon ‘Fino 49’ under field conditions: Water relations,osmotic adjustment and gas exchange

Drought and salinity are two of the most important factors limiting the lemon yield in south-eastern Spain. The effects of drought and salt stress, applied independently, on water relations, osmotic adjustment and gas exchange in the highest evapotranspiration period were studied to compare the tolerance and adaptive mechanisms of 13-year-old ‘Fino 49’ lemon trees, in immature and mature leaves. The study was carried out in an experimental orchard located in Torre Pacheco (Murcia). Three treatments were applied: Control, well-irrigated; drought-stress (DS), non-irrigated from 15th May to 7th July and salinity, irrigated with 30 mM NaCl from 1st March to 7th July. At the end of the experiment, only DS trees showed a decreased leaf stem water potential (Ψ_md). Under DS conditions, both types of leaf lost turgor and did not show any osmotic or elastic mechanism to maintain leaf turgor. Osmotic adjustment was the main tolerance mechanism for maintenance of turgor under salt stress, and was achieved by the uptake of Cl⁻ ions. Gas-exchange parameters were reduced by DS but not by salinity, stomatal closure being the main adaptive mechanism for avoidance of water loss and maintenance of leaf turgor. Salinity gave rise to greater Cl⁻ accumulation in mature than in immature leaves. The increase of proline in immature leaves due to DS indicates greater damage than in mature leaves.     

水分胁迫对长柄扁桃叶片含水量及保护酶活性的影响

利用PEG-6000根际模拟土壤水分胁迫的方法,对长柄扁桃(Amygdalus pedunculata)幼苗进行了不同程度的水分胁迫处理,研究在不同水分胁迫下长柄扁桃叶片相对含水量及膜脂过氧化作用的变化。结果表明,随着胁迫时间的延长和胁迫强度的加大,叶片相对含水量持续下降,MDA和质膜透性逐渐增大,但在胁迫的前期,下降和上升幅度相对较小。POD活性在不同程度水分胁迫下表现出先降后升的趋势,CAT活性表现出先升后降的趋势,在轻、中度胁迫下SOD活性先升而后降低,在重度胁迫下呈现出降、升、降的变化。三种酶活性在胁迫结束时除重度胁迫处理略低于对照外,其余各处理均高于对照,表明长柄扁桃对干旱有较强的适应能力。