Ballhorn Daniel J, Lieberei Reinhard, Ganzhorn Jörg U
Biocenter Klein Flottbek and Botanical Garden, University of Hamburg, Germany.
J Chem Ecol. 2005 Jul;31(7):1445-73. doi: 10.1007/s10886-005-5791-2.
Quantitative experimental results on the antiherbivorous effect of cyanogenesis are rare. In our analyses, we distinguished between the total amount of cyanide-containing compounds stored in a given tissue [cyanogenic potential (HCNp)] and the capacity for release of HCN per unit time (HCNc) from these cyanogenic precursors as a reaction to herbivory. We analyzed the impact of these cyanogenic features on herbivorous insects using different accessions of lima beans (Phaseolus lunatus L.) with different cyanogenic characteristics in their leaves and fourth instars of the generalist herbivore Schistocerca gregaria Forskål (Orthoptera, Acrididae). Young leaves exhibit a higher HCNp and HCNc than mature leaves. This ontogenetic variability of cyanogenesis was valid for all accessions studied. In no-choice bioassays, feeding of S. gregaria was reduced on high cyanogenic lima beans compared with low cyanogenic beans. A HCNp of about 15 micromol cyanide/g leaf (fresh weight) with a corresponding HCNc of about 1 micromol HCN released from leaf material within the first 10 min after complete tissue disintegration appears to be a threshold at which the first repellent effects on S. gregaria were observed. The repellent effect of cyanogenesis increased above these thresholds of HCNp and HCNc. No repellent action of cyanogenesis was observed on plants with lower HCNp and HCNc. These low cyanogenic accessions of P. lunatus were consumed extensively--with dramatic consequences for the herbivore. After consumption, locusts showed severe symptoms of intoxication. Choice assays confirmed the feeding preference of locusts for low over high cyanogenic leaf material of P. lunatus. The bioassays revealed total losses of HCN between 90 and 99% related to the estimated amount of ingested cyanide-containing compounds by the locusts. This general finding was independent of the cyanogenic status (high or low) of the leaf material.
关于氰化物生成的抗食草动物作用的定量实验结果很少。在我们的分析中，我们区分了储存在给定组织中的含氰化合物总量[氰化潜力（HCNp）]以及这些氰化前体在遭受食草动物侵害时每单位时间释放HCN的能力（HCNc）。我们使用叶片具有不同氰化特征的不同菜豆品种（菜豆）以及多食性食草动物沙漠飞蝗（直翅目，蝗科）的四龄幼虫，分析了这些氰化特征对食草昆虫的影响。幼叶比成熟叶表现出更高的HCNp和HCNc。氰化物生成的这种个体发育变异性对所有研究的品种都有效。在无选择生物测定中，与低氰化菜豆相比，沙漠飞蝗在高氰化菜豆上的取食减少。在完全组织解体后的前10分钟内，叶片材料中释放出约15微摩尔氰化物/克叶（鲜重）的HCNp以及相应约1微摩尔HCN的HCNc似乎是观察到对沙漠飞蝗产生首次驱避作用的阈值。氰化物生成的驱避作用在这些HCNp和HCNc阈值之上增强。在HCNp和HCNc较低的植物上未观察到氰化物生成的驱避作用。这些低氰化的菜豆品种被大量食用——对食草动物产生了严重后果。食用后，蝗虫表现出严重的中毒症状。选择测定证实了蝗虫对菜豆低氰化叶片材料的取食偏好高于高氰化叶片材料。生物测定显示，与蝗虫摄入的含氰化合物估计量相比，HCN的总损失在90%至99%之间。这一普遍发现与叶片材料的氰化状态（高或低）无关。
