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21.
Elena Valkama Minna Kivimenp Helin Hartikainen Anu Wulff 《Agricultural and Forest Meteorology》2003,120(1-4):267
The possible ameliorative effects of selenium (Se) addition to soil on the detrimental effects of enhanced UV-B radiation were tested on strawberry and barley during 4 months of field experiment in Kuopio, Central Finland. Control plants were exposed to ambient levels of UV radiation, using arrays of unenergized lamps. A control for UV-A radiation was also included in the experiment. Added Se, applied as H2SeO4, at the level of 0.1 mg kg−1 soil (low dosage) and 1 mg kg−1 soil (high dosage) increased Se concentrations in plants more than 10 and 100 times, respectively. After 4 months of exposure, strawberry and barley plants were harvested for biomass analysis. Chlorophyll fluorescence was measured using the Hansatech FMS2 fluorescence monitoring system. Leaf anatomy and ultrastructure were observed by light and transmission electron microscope. Several effects of UV and Se as well as their interaction were found, mostly for strawberry, but not for barley, indicating species-specific responses. Our results provided evidence that the high Se concentration in soil had no ameliorative effect but increased the sensitivity of strawberry to enhanced UV-B radiation in the field. Under ambient radiation, Se did not alter leaf growth of strawberry, whereas under UV-B radiation, the high Se addition significantly decreased leaf growth. Strawberry runner biomass was affected by the interaction of Se and UV. Under ambient radiation Se did not change dry weight of runners, but in combination with UV-A or UV-B radiation the high Se dosage decreased dry weight of runners by about 30%. Although the high Se concentration positively influenced on quantum efficiency of photosystem II (PSII) in strawberry leaves, it reduced runner biomass, leaf number and ratio of starch to chloroplast area. This suggests that the harmful effects of the high Se dosage on photosynthetic processes occurred as a result of changes in activity or/and biosynthesis of enzymes, rather than alteration of PSII. At the low concentration, Se effects were slight and variable.Although barley leaves accumulated higher Se concentrations than strawberry, there were no apparent changes in their growth, biomass or chlorophyll fluorescence due to Se effect either alone or in combination with UV-B. However, at the ultrastructural level, an enlargement in the peroxisome area was found due to combination of UV radiation with Se, suggesting the activation of antioxidative enzymes, possibly catalase. Decrease in mitochondrial density in barley cells in response to Se might be attributed to alteration of mitochondrial division. Increase in the proportion of cells with cytoplasmic lipid bodies due to combined effect of UV-B and Se indicated the alteration of lipid metabolism and the acceleration of cell senescence in barley. Main UV-B effects were found, mostly at the tissue and ultrastructural level in strawberry, but not in barley, indicating species-specific susceptibility to enhanced UV-B radiation. UV-B-treated strawberry plants developed marginally thinner leaves with reduced ratio of starch to chloroplast area in their cells, suggesting negative influence of UV-B on photosynthetic processes. 相似文献
22.
Air sacs are considered to be one of the controlling factors of bird behaviour and habits in addition to their roles in ventilation, regulating body temperature, swimming and flight. As a scavenger and an omnivorous flight bird, air sacs of the hooded crow were the focus of this study. Eight healthy, adult hooded crows were used to examine the morphological characteristics of the air sacs, which were examined grossly and with latex and cast preparations. In general, the morphological overview of the hooded crow air sacs is similar to other avian species. We observed nine air sacs; four paired sacs (cervical, cranial thoracic, caudal thoracic and abdominal air sacs) and one unpaired sac; the clavicular air sac. The cervical air sac communicated to the lung through the medioventral bronchus and had three diverticula; intermuscular, subscapular and subcutaneous. The clavicular air sac communicated with lung through the medioventral bronchus and had subscapular, axillary, humeral, subpectoral and sternal diverticula. The cranial and caudal thoracic air sacs were communicated with lung through the lateroventral bronchi and the both sacs did not have any diverticula. The abdominal air sacs were posterior to the caudal thoracic air sacs. The left abdominal sac was the largest air sac. The right and left abdominal sacs gave off branches to diverticula that pneumatized synsacrum. The abdominal air sacs gave off femoral diverticula behind the hip joint as well as perirenal diverticula. 相似文献
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Bonnie J. Smith DVM PhD Stephen A. Smith DVM PhD 《Veterinary radiology & ultrasound》1991,32(2):87-95
The purpose of this study was to provide a reference for xeroradiographic and conventional radiographic anatomy of the mallard duck ( Anas platyrhynchos ) as a representative of the avian Order Anseriformes. The head, body, wing, and pelvic limb of three adult birds were radiographed using xeroradiographic and conventional radiographic techniques. Nine xeroradiographs and their corresponding conventional radiographs were selected, and the xeroradiographs labeled to illustrate normal anatomy. Selected views of other anseriform species were included to illustrate certain anatomical features unique to those species. 相似文献
25.
行动导向教学法是一种以培养学生的关键能力和职业行为能力为目标的新的教学方法,在宠物解剖学中运用行动导向教学法可以达到事半功倍的教学效果。 相似文献
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郁金香花芽分化的解剖学研究 总被引:3,自引:0,他引:3
利用石蜡切片法研究了郁金香花芽分化的进程及温度变化对花芽分化的影响。结果表明:郁金香鳞茎内顶端生长点的分化过程可以分为营养生长期,生殖茎端形成期,花器官分化期,花器官伸长期4个时期花芽分化从7月上旬开始,8肿旬结束。在贮藏期间,郁金香鳞茎内顶端生长点前期发育速度较慢,后期发育速度较快,并按由外向内的顺序进行。 相似文献
28.
【目的】基于定量解剖方法探究桃花心木属3种树种木材的构造特征,揭示其不同构造特征的种间和种内变异规律,为木材“种”水平的准确识别提供科学依据。【方法】针对大叶桃花心木、桃花心木和矮叶桃花心木木材标本显微切片,通过光学显微镜采集其横、径、弦三切面微观构造图像,利用图像分析软件分别测量导管分子长度、管孔弦向直径、管孔频率、木纤维长度、木射线宽度、木射线高度和木射线频率7个定量解剖特征,分析其不同构造特征的种间和种内变异规律;采用随机森林算法对木材树种进行识别,比较木材不同定量解剖特征对识别准确率的贡献度。【结果】3种桃花心木木材显微切片图像中管孔、轴向薄壁组织和木射线等构造特征相似,通过人工方式难以区分;除木射线宽度外,其他6组定量解剖特征在种间均存在显著差异;随机森林算法对桃花心木的识别准确率达86.67%,7个定量解剖特征对木材识别结果的贡献度存在差异,其中导管分子长度的平均准确率降低度值(3.956)和平均基尼指数降低度值(6.311)最大,管孔弦向直径次之,木射线宽度的平均准确率降低度值(0.797)和平均基尼指数降低度值(2.175)最小,表明导管分子长度的贡献度最大,木射线宽度的贡献度最小。【结论】采用木材定量解剖方法,揭示3种桃花心木构造特征的种间和种内变异规律以及在木材识别中起关键作用的定量解剖特征,可为实现木材“种”水平的准确识别提供科学依据。 相似文献
29.
为摸清我国橡胶树(Hevea brasiliensis)品系间的叶片形态结构差异,为高光效品种选育及适应性评价等提供依据,以‘热研73397’、‘热研917’等21份我国橡胶树主要栽培品系为实验材料,采用石蜡切片技术和指甲油印迹法,观测了不同品系橡胶树叶片栅栏组织、海绵组织厚度等叶片结构特征。结果表明:‘南华1’、‘红星1’以及‘热研917’品系的栅栏组织结构厚度、叶片厚度,栅栏组织与海绵组织的比值等较高;‘热垦628’、‘热研106’与‘热研917’的气孔长度,气孔宽度和气孔密度相对较小,推测具有较强的光合能力和一定的抗旱能力。采用系统聚类将上述品种进行分成2类,其中,‘南华1’,‘红星1’,‘海垦1’,‘热研917’品系的叶片厚度,栅栏组织,组织结构致密度相对较高。综上,‘南华1’,‘红星1’,‘热研917’品系叶片厚度,栅栏组织,组织结构致密度较高,气孔小而密,推测其有更好的光合性能。 相似文献
30.
核桃生理落果的解剖学观察 总被引:1,自引:0,他引:1
核桃生理落果(包括落花)只有1次高峰,高峰期出现在盘花后2周,落果的离层形成部位有2个:一是在结果枝和结果母枝连接处,一是在果实基部。对果实进行解剖研究表明,一部分落果的子房内壁细胞解体、珠被和隔膜组织发育不良,另一部分的解剖结构与正常果无差异。根据离层形成部位和果实败育程度将核桃的生理落果分为前期落果、中期落果和后期落果,初步分析造成前两期落果的主要原因是由于春季雌花分化不完全,从而导致雌花和幼果的败育。 相似文献