排序方式： 共有6条查询结果，搜索用时 15 毫秒
1
1.
用焦锑酸钙沉淀的电镜细胞化学方法，研究了白骨壤叶片衰老过程中叶肉细胞Ca^2 水平的变化．结果表明，在白骨壤幼叶和成熟叶叶肉细胞中，焦锑酸钙沉淀颗粒大量出现在液池和细胞间隙中，细胞壁中也可见少量沉淀，而细胞基质中则看不到焦锑酸钙沉淀．在衰老叶中，细胞基质和细胞膜上焦锑酸钙沉淀增加，而液泡和细胞间隙中的锑酸钙沉淀则显著减少，并且叶绿体外膜部分破损，结构破坏，核膜与液泡膜内部结构模糊，叶绿素含量、净光合速率、气扎手率和蒸腾速率显著下降．Ca^2 的区域性分布的变化与植物叶片衰老密切相关。 相似文献
2.
红树叶片衰老过程中活性氧和保护酶活性的变化 总被引：2，自引：0，他引：2
测定了红树植物木榄(Bruguiera gymnorrhiza)和秋茄(Kandelia candel)幼叶、成熟叶和老叶间活性氧和三种细胞保护酶活性的变化。结果表明,在叶片衰老过程中,丙二醛和H2O2含量显著提高,超氧化物自由基产生速率加快,表明红树叶片衰老中膜脂过氧化作用增强,并且与H2O2和超氧化物自由基含量的上升相关。在3种细胞保护酶中,超氧化物歧化酶(SOD)活性逐渐降低,过氧化物酶(POD)活性显著提高,过氧化氢酶(CAT)活性在叶片成熟过程中增高,随着衰老而急剧降低,细胞保护酶酶活的变化直接影响了叶片衰老过程中活性氧代谢的平衡。 相似文献
3.
本研究分析了九龙江口红树植物秋茄(Kandelia obovata)和桐花树(Aegiceras corniculatum),以及盐沼植物互花米草(Spartina alterniflora)和短叶茳芏(Cyperus malaccensis)不同状态(成熟、衰老和腐烂)叶片中脂肪酸组成及相对含量。结果共检测出20种脂肪酸,其中9种存在于所有样品中。样品中含量最高的饱和脂肪酸均为棕榈酸C16:0 (21.76%～39.55%),其次是硬脂酸C18:0 (4.98%～29.88%);不饱和脂肪酸主要有油酸C18:1n9 (2.04%～12.90%)、亚油酸C18:2n6 (8.25%～24.69%)和C20:1n9 (1.64%～40.45%)。红树植物和盐沼样品中的脂肪酸组成存在差异,C30:0为红树植物的特征脂肪酸。在植物衰老和腐烂的样品中的脂肪酸组成与新鲜成熟样品存在差异,C20:1n9在衰老的样品中出现明显的下降,而相比红树植物两种盐沼植物的C20:1n9含量则下降更快。研究结果表明,总体上湿地植物在衰老和腐烂后不饱和脂肪酸占脂肪酸的比例明显下降,而必需脂肪酸C18:2n6的水平则未出现升高。 相似文献
4.
5.
Unmanned Aerial Vehicles(UAVs) have become popular and their use in agriculture monitoring is attracting more and more attention. There has emerged another class of agricultural UAVs whose normal consumer grade Red/Green/Blue(RBG) bands cameras have been modified to include the Near-Infrared(NIR) band by replacing one of the visible channel bands. This reduces the cost for agricultural UAVs. However, few researches have assessed the suitability of these modified UAV cameras in agricultural remote sensing. This study employed a modified UAV consumer grade camera with Blue/Green/Near Infra-red(BGNIR) bands to assess its applicability in crop remote sensing monitoring. Two experimental fields in Eastern Zimbabwe were used to assess the applicability of the modified BGNIR UAV camera in potato stress detection, maize senescence monitoring and chlorophyll concentration variations in bananas. Processed Green Normalized Vegetation Index(GNDVI) maps from the UAV imagery were compared with actual ground data of geo-tagged images taken during the UAV flights. Visual comparison between the ground and UAV imagery showed positive correlation. Highly stressed potato plants had lower GNDVI values than the healthier looking plants. Matured maize canopies also had lower GNDVI values than the late mature plants whose leaves were still green. GNDVI values in bananas from the first flight ranged from 0.094 91 to 0.334 74 and after the application of Nitrogen/Phosphorous/Potassium(NPK) fertilizer the GNDVI values ranged from 0.124 61 to 0.555 64. Increase in nitrogen also increases chlorophyll concentration in plant leaves hence the values of GNDVI increase after fertilization. We conclude that consumer grade modified UAV cameras are suitable in remote sensing of agricultural crops. Their adoption and utilization reduce the cost burden on farmers in developing countries especially in Africa, and help them to monitor their crops more efficiently. 相似文献
6.
LICHENOMETRIC DATING (LICHENOMETRY) AND THE BIOLOGY OF THE LICHEN GENUS RHIZOCARPON: CHALLENGES AND FUTURE DIRECTIONS 
下载免费PDF全文
下载免费PDF全文 RICHARD A. ARMSTRONG 《Geografiska Annaler: Series A, Physical Geography》2016,98(3):183-206
Lichenometric dating (lichenometry) involves the use of lichen measurements to estimate the age of exposure of various substrata. Because of low radial growth rates and considerable longevity, species of the crustose lichen genus Rhizocarpon have been the most useful in lichenometry. The primary assumption of lichenometry is that colonization, growth and mortality of Rhizocarpon are similar on surfaces of known and unknown age so that the largest thalli present on the respective faces are of comparable age. This review describes the current state of knowledge regarding the biology of Rhizocarpon and considers two main questions: (1) to what extent does existing knowledge support this assumption; and (2) what further biological observations would be useful both to test its validity and to improve the accuracy of lichenometric dates? A review of the Rhizocarpon literature identified gaps in knowledge regarding early development, the growth rate/size curve, mortality, regeneration, competitive effects, colonization, and succession on rock surfaces. The data suggest that these processes may not be comparable on different rock surfaces, especially in regions where growth rates and thallus turnover are high. In addition, several variables could differ between rock surfaces and influence maximum thallus size, including rate and timing of colonization, radial growth rates, environmental differences, thallus fusion, allelopathy, thallus mortality, colonization and competition. Comparative measurements of these variables on surfaces of known and unknown age may help to determine whether the basic assumptions of lichenometry are valid. Ultimately, it may be possible to take these differences into account when interpreting estimated dates. 相似文献
1