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941.
内蒙高腐殖酸地下水中碘的分布特征与IDD病的关系 总被引:3,自引:1,他引:2
为探讨碘在高腐植酸地下水中的分布特征 ,研究内蒙古河套平原地区 51份水样 .分析结果显示 ,水质偏碱 (平均值 pH=7.91 ) ,水中腐植酸和 COD含量均高 ,地下水类型属于 HCO3-Na和 HCO3-Cl- Na型 .在这种高还原型盐水环境中水碘平均浓度达到 430 μg/L,超过了水碘安全浓度范围的上限 ( 5~ 200μg/L) .相关分析结果显示 ,水碘浓度与其它因素的相关顺序是 :COD>荧光强度 >电导率 >HCO-3>Cl->Na+>pH>As>井深 .当地地下水中碘的分布呈现出碘浓度随腐植酸含量和盐渍化程度增加而增加的趋势 .由于这些因素的综合作用 ,当地没有发生高碘型碘缺乏病 ( IDD)的大面积流行 . 相似文献
942.
研究了不同条件下胡敏酸在土壤中的迁移过程.结果表明,其迁移过程表现出较大的差异,在溶液pH值、胡敏酸浓度和溶液流速均较高时,胡敏酸迁移的阻滞因子和在土壤中的吸附系数均较低,有利于胡敏酸在土壤中的迁移;在溶液pH值、胡敏酸浓度和溶液流速均较低时,土壤对胡敏酸迁移的阻滞作用较大.胡敏酸的迁移还与土壤性质有关,土壤黏粒含量和阳离子交换量越高,胡敏酸在土壤中吸附的越多,越不利于迁移.在土壤中的吸附是胡敏酸迁移的主要控制因素,在预测胡敏酸在水土环境中迁移时,应该充分考虑不同条件下胡敏酸在不同性质土壤中的吸附. 相似文献
943.
944.
945.
Summary. Tannins are plant defense compounds that exhibit antibiotic (e.g. toxic) and antixenotic (e.g. repellent) effects against
an array of plant pests. They are broadly divided into two major groups, hydrolysable tannins (gallotannins and ellagitannins)
and proanthocyanidins, each with an undetermined number of compounds. We investigated constitutive levels of hydrolysable
tannins and proanthocyanidins in the leaves and stems of American (Castanea dentata Marshall) (Fagales: Fagaceae) and Chinese (C. mollissima Blume) chestnut. American chestnut contained more proanthocyanidins in leaves and stems than Chinese chestnut, but Chinese
chestnut contained more foliar hydrolysable tannins. Regardless of these differences, gypsy moth (Lymantria dispar L, Lepidoptera: Lymantriidae) performance did not differ when fed American and Chinese chestnuts. We also investigated the
effects of jasmonic acid (JA) treatment on differential tannin induction in American and Chinese chestnut leaves and stems.
JA treatment increased proanthocyanidins in American chestnut stems and hydrolysable tannins in both tissue types of American
chestnut, but did not influence tannin concentrations in Chinese chestnut leaves or stems. HPLC-ESI-MS analysis of pooled
samples suggested that hydrolysable tannins in each tissue were qualitatively comprised primarily of ellagitannins, and JA
generally increased the number of hydrolysable tannins that could be detected by ESI-MS. Third, we investigated the performance
of gypsy moths on JA treated and untreated American and Chinese chestnut. Caterpillar relative growth was not influenced by
JA treatment on Chinese chestnut, but decreased in response to JA application on American chestnut. Our results indicate that
JA-dependent defenses differ between these chestnut species. This study improves our understanding of ecologically important
differences in tannin induction and herbivore susceptibility in Castanea, and has important implications in efforts for American chestnut restoration and commercial chestnut production. 相似文献
946.
水杨酸对梨叶感染轮纹菌后脂肪酸、叶绿素荧光参数和叶绿体超微结构的影响 总被引:1,自引:0,他引:1
用0.3 mmol L-1水杨酸预先处理梨叶片,3 d后接种轮纹病菌(Physalospora Piricola Nose),接种3 d后开始测定各种指标,随后每隔3 d测定1次,共5次.结果表明,经SA处理的梨叶片,感染轮纹病菌后不饱和脂肪酸含量(UFA)、不饱和脂肪酸指数(IUFA)、叶绿素含量、原初光能转换效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、光合电子传递量子效率(ΦPSⅡ)和光化学猝灭系数(qP)比未经SA处理的相应提高;非光化学猝灭系数(qN)比未经SA处理的相应下降.电镜观察表明,部分叶绿体膨大,变形;基粒片层弯曲、散开;淀粉粒数量减少;经SA处理后,症状减轻.图3表1参20 相似文献
947.
Variations between rice cultivars in root secretion of organic acids and the relationship with plant cadmium uptake 总被引:13,自引:0,他引:13
To attempt to understand certain mechanisms causing the variations between rice cultivars with regard to Cd uptake and accumulation,
pot soil experiments were conducted with two rice cultivars at different levels of Cd, i.e., 0 (the control), 10, 50 mg Cd
kg−1 soil. The two rice cultivars differ significantly with regard to Cd uptake and accumulation. Root secretions of low-molecular-weight
organic acids (LMWOA) for each treatment were measured with ion chromatography. The results showed that LMWOA concentrations
in the soil planted with Shan you 63 (a high soil Cd accumulator) were all higher than those in the soil planted with Wu yun jing 7 (low soil Cd accumulator) at different soil Cd levels, although the magnitudes of the differences varied for individual LMWOA
and depend on soil Cd concentrations. For all six LMWOA, there were significant differences at P < 0.05 or < 0.01 levels for soils treated with 10 and 50 mg kg−1 Cd. The magnitude of the differences was greater under soil Cd treatments, especially at relatively low levels (for example,
10 mg Cd kg−1 soil), than in the control. Acetic acid and formic acid constituted more than 96% of the total concentration of the six LMWOA,
while citric acid constituted only about 0.1%. The rice cultivar with higher concentrations of LMWOA in soil accumulated more
Cd in the plants. The results indicate that LMWOA secretion by rice root, especially in Cd-contaminated soils, is likely to
be one of the mechanisms determining the plant Cd uptake properties of rice cultivars. 相似文献
948.
研究了不同浓度的柠檬酸、草酸、苹果酸对蛇纹岩发育土壤镍(Ni)、钴(Co)的活化效果.结果表明,在较低浓度(<10mmol/L)时,3种有机酸对土壤中的Ni、Co活化效果均较差.柠檬酸对元江、墨江土壤Ni的最大活化比例分别为9.1%、12.9%,远大于其他2种有机酸(P<0.05).各有机酸活化能力的大小为柠檬酸>草酸>苹果酸,同时Ni、Co活化量之间存在一定的相关性.基于结合率与Ni、Co活化量的考虑,在蛇纹岩发育土壤的化学修复或螯合诱导植物修复中,10~30mmol/L的有机酸是较为适合的浓度.草酸在50mmol/L时,对Ni、Co的活化效果有所降低. 相似文献
949.
Introduction Photosyntheticphotonfluxdensity(PPFD)withinforestcanopiesisintrinsicallyheterogeneousinspaceandtime.Becausesomespeciesaregenotypicallysuitedforspecificlightregimes,understandingtheheterogeneityofthelightregimewithinaforestcanopyisimportantfor… 相似文献
950.
Effects of simulated acid rain on fertility of litchi 总被引:1,自引:0,他引:1
The regulatory role of calcium in fertility of pollen and pistil under simulated acid rain was investigated. The germination percentage of pollen treated with acid rain of pH 4.5 was 9.42% lower than that of control, and that of pH 3.5, pH 2.5 and pH 1.5 were 22.47%, 45.49% and 71.62%, respectively. Simultaneously, the injury character of pollen was obviously observed when flowers were treated with acid rain of pH 3.5. The difference in fruit setting rate between the female flower treated with acid rain of pH 4.0 and the control was significant at p 〈 0.05. Ca(NO3 )5 of 0.2-0.4 mmol/L could promote pollen germination under the stress of acid rain. The beneficial function was reduced when calcium concentration surpassed 0.8 mmol/L. Spraying 2 mmol/L Ca(NO3 )5 reduced the injury of acid rain to pistil and increased fruit-setting rate significantly. The physiological importance of calcium during pollen germination and pistil development was also discussed. 相似文献