Berenbaum M R
Section of Ecology and Systematics, 135 Insectary, Cornell University, 14853, Ithaca, NY, USA.
Oecologia. 1981 May;49(2):236-244. doi: 10.1007/BF00349195.
Seasonal changes in the distribution and abundance of furanocoumarins in wild parsnip, Pastinaca sativa (Umbelliferae), were examined in a population of plants in Tompkins County, New York. Xanthotoxin, imperatorin and bergapten (linear furanocoumarins) occur in all above-ground parts of the plant; in addition, angelicin and sphondin (angular furanocoumarins) occur in umbels of some individuals. Total furanocoumarin content, as measured by percent dry weight, is greatest in reproductive parts, particularly buds and seeds; variation in concentrations between plants is greatest in vegetative structures (e.g., leaves).Within the plant, the distribution of furanocoumarins is significantly correlated with nitrogen, as opposed to biomass, allocation. In that nitrogen is often a factor limiting the plant growth, furanocoumarins appear to be allocated in proportion to plant tissue value; reproductive structures, obvious contributors to plant fitness, contain over ten times the amount of nitrogen and furanocoumarin contained in vegetative structures such as senescent leaves.Stepwise multiple regression analysis revealed that generalized insect herbivores tend to feed on plants or plant parts low in furanocoumarin content and, correspondingly, low in nitrogen content. Parsnip specialists, notably Depressaria pastinacella (Lepidoptera: Oecophoridae), feed exclusively on umbels, plant parts rich in nitrogen and furanocoumarins; furanocoumarin number and content in fact account for over 60% of the variance in number of umbel feeders. These patterns conform with previous determinations of the toxicological properties of furanocoumarins. Nitrogen is known to affect growth rate, fecundity, longevity and survivorship of insect herbivores; by tolerating or detoxifying furanocoumarins, D. pastinacella can consume plant tissues containing significantly greater amounts of nitrogen than tissues consumed by generalist feeders. That the presence of D. pastinacella on individual plants is correlated with the number of furanocoumarins present is consistent with the hypothesis that parsnip specialists use angular furanocoumarins as host recognition cues.
在纽约汤普金斯县的一个野生欧洲防风草（Pastinaca sativa，伞形科）种群中，研究了呋喃香豆素在其体内分布和含量的季节性变化。黄原毒素、欧前胡素和佛手柑内酯（线性呋喃香豆素）存在于植株的所有地上部分；此外，当归素和sphondin（角型呋喃香豆素）存在于部分植株的伞形花序中。以干重百分比衡量，呋喃香豆素的总含量在生殖部位最高，尤其是芽和种子；植株间浓度的变化在营养结构（如叶子）中最大。在植株内部，呋喃香豆素的分布与氮的分配显著相关，而非与生物量分配相关。鉴于氮常常是限制植物生长的一个因素，呋喃香豆素似乎是按照植物组织价值的比例进行分配的；生殖结构对植物适合度有明显贡献，其含有的氮和呋喃香豆素的量是诸如衰老叶片等营养结构的十倍以上。逐步多元回归分析表明，一般的食草昆虫倾向于取食呋喃香豆素含量低且相应地氮含量也低的植物或植物部分。欧洲防风草专食性昆虫，尤其是欧洲防风草巢蛾（Depressaria pastinacella，鳞翅目：巢蛾科），只取食伞形花序，即富含氮和呋喃香豆素的植物部分；实际上，呋喃香豆素的数量和含量占伞形花序取食者数量变异的60%以上。这些模式与先前对呋喃香豆素毒理学特性的测定结果相符。已知氮会影响食草昆虫的生长速率、繁殖力、寿命和存活率；通过耐受或解毒呋喃香豆素，欧洲防风草巢蛾能够取食含氮量比一般取食者所取食组织显著更高的植物组织。欧洲防风草巢蛾在单株植物上的出现与呋喃香豆素的数量相关，这与欧洲防风草专食性昆虫利用角型呋喃香豆素作为寄主识别线索的假设一致。
