Flavonoid diversity and geographic endemism in Parthenium

The distribution of 34 flavonoids detected in the North American species of Parthenium indicates that flavonoid diversity and structural types are correlated with biological aspects of different species types. Widespread species occurring in a variety of habitat types are characterized by greater numbers of flavonoids, primarily as the result of flavonoid glycoside diversity; while species which are geographically isolated in limestone or gypsum habitats are characterized by a tendency to depauperate flavonoid patterns with major methylated aglycone components. The possibility that glycosylation is related to self-detoxification and preservation of toxic phenolic potential is discussed. It is shown that parallel chemical adaptations, similar to the well-known parallel morphological adaptations of unrelated species which coexist in certain habitats, may occur     

喜钙和嫌钙植物对外源Ca2+的生长生理响应

以喜钙植物伞花木和嫌钙植物大白杜鹃为实验材料,以Hoagland营养液并设置其Ca2+浓度分别为0、5、10、25、50mmol/L培养试验,比较不同浓度外源Ca2+对其生长、叶绿素含量、渗透调节和矿质元素积累的影响,探索喜钙植物生长的适应特征,为喀斯特地区喜钙植物嗜钙机制研究提供基础资料。结果显示:(1)随着外源Ca2+浓度的增加,伞花木植株高度、茎粗以及叶干重、叶长、叶宽和叶形指数均得到不同程度提高,叶绿素和可溶性蛋白质含量增加,脯氨酸和可溶性糖含量无显著变化;而嫌钙植物大白杜鹃的生长却受到抑制,叶绿素和蛋白质含量降低,脯氨酸和可溶性糖含量增加;当Ca2+浓度为50mmol/L时,伞花木叶绿素和蛋白质含量分别为2.99mg/g和17.10mg/g,大白杜鹃叶绿素和蛋白质含量分别为1.39mg/g和14.30mg/g。(2)在实验设置的钙范围内,Ca2+可促进伞花木对P、N吸收并稳定体内Ca、K动态;而低浓度的Ca2+(<10mmol/L)促进大白杜鹃对Ca累积,抑制N、P吸收。     

Where does all the calcium go? Evidence of an important regulatory role for trichomes in two calcicoles

In previous studies of the calcicoles Centaurea scabiosa and Leontodon hispidus, the stomata on isolated epidermis closed partially when the concentration of calcium in the medium was above 1 mol m^?3. This is a much smaller concentration than that believed to be delivered into the leaves in xylem sap when the plants are growing in a calcium-rich medium, and hence the mechanism for ‘protecting’ stomata from excessive exposure to free calcium is thought to be of great physiological significance. It is shown here that, in the leaves of both species, a substantial amount of the calcium they contain is located within meso-phyll cells, and virtually all of that which does enter the epidermis is contained within trichomes, probably as calcium oxalate. The amounts of calcium in the vicinity of the stomata thus remain small despite high concentrations elsewhere, ensuring that the essential role of Ca²⁺ in intra-cellular signalling in guard cells can continue to be performed without disturbance.