Chemical and physical defense of weed seeds in relation to soil seedbank persistence
Chemical and physical defense of weed seeds in relation to soil seedbank persistence
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DOI：
10.1614/ws-07-196.1
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发表时间：
2008-09-01
期刊：
影响因子：
2.5
通讯作者：
Renner, Karen A.
中科院分区：
文献类型：
--
作者：
Davis, Adam S.;Schutte, Brian J.;Renner, Karen A.
有效的杂草种子库管理需要对土壤种子库中种子持久性的生态决定因素进行机械理解。定量分析了普通羊蹄草种子、野pennyweed种子、巨尾草种子、地瓜种子、绒叶种子和黄尾草种子的化学防御和物理防御与种子库短期和长期持久性的关系。邻二羟基酚（o-DHP）是一类被认为具有种子防御作用的化合物，其种子含量在保护程度最低的物种（普通羊蹄草，9.2 μ g种子（-1））和保护程度最高的物种（野脚草，34.1 μ g种子（-1））之间差异超过三倍。种子o-DHP与种子在土壤中的半衰期呈负相关（r = -0.77, P < 0.001），与埋藏试验中种子的短期持久性呈负相关（r = -0.82, P < 0.05）。与物理种子保护相比，化学种子保护的相对重要性（以种子o-DHP浓度与种皮厚度之比表示）随着种子短期持久性的增加呈线性降低（r = -0.96, P < 0.01），随着土壤种子库中种子长期持久性的增加呈非线性降低（y = 0.16 + 0.21/(0.0432 + x), r -2 = 0.99, P < 0.001）。通过刺穿、切片或研磨处理对种皮造成的机械损伤，增加了所有六种在掩埋期间的短期死亡率。穿孔种子死亡率与种子酚浓度呈负相关（r = -0.35, P < 0.05），与种子半衰期（r = 0.42, P < 0.01）和种皮厚度呈正相关（r = 0.36, P < 0.05）。种子酚类物质支持了o-DHPs的结果。总的来说，这些发现表明，在种子库管理方面，杂草种子防御的构建方式存在潜在的弱点。具有瞬时种子库的杂草似乎比具有高度持久种子库的杂草在化学防御方面投入更多。因此，后一类种子相对更依赖于种子的物理保护以在土壤种子库中持续存在，并且更容易受到降低杂草种皮物理完整性的管理策略的影响。
Effective weed seedbank management requires mechanistic understanding of ecological determinants of seed persistence in the soil seedbank. Chemical and physical defense of common lambsquarters, field pennycress, giant foxtail, kochia, velvetleaf, and yellow foxtail seeds were quantified in relation to short- and long-term seedbank persistence. Seed content of ortho-dihydroxyphenois (o-DHP), a class of putative seed defense compounds, varied more than threefold between the least protected species (common lambsquarters, 9.2 mu g g seed(-1)) and the most protected species (kochia, 34.1 mu g g seed(-1)). Seed o-DHP was inversely related (r = -0.77, P < 0.001) to seed half-life in the soil and to short-term seed persistence in burial assays (r = -0.82, P < 0.05). The relative importance of chemical seed protection in comparison to physical seed protection, as represented by the ratio of seed o-DHP concentration to seed coat thickness, decreased linearly with increasing short-term seed persistence (r = -0.96, P < 0.01) and nonlinearly with increasing long-term seed persistence in the soil seedbank (y = 0.16 + 0.21/(0.0432 + x), R-2 = 0.99, P < 0.001). Mechanical damage to the seed coat, via piercing, slicing, or grinding treatments, increased short-term mortality during burial for all six species. Mortality of pierced seeds was negatively associated (r = -0.35, P < 0.05) with seed phenol concentration and positively associated with seed half-life (r = 0.42, P < 0.01) and seed coat thickness (r = 0.36, P < 0.05). Seed phenolics, as a class, supported the results for o-DHPs. Overall, these findings suggest a potential weakness, with respect to seedbank management, in the way weed seed defenses are constructed. Weed species with transient seedbanks appear to invest more in chemical defense than those species with highly persistent seedbanks. As a result, seeds in the latter category are relatively more dependent upon physical seed protection for persistence in the soil seedbank, and more vulnerable to management tactics that reduce the physical integrity of the weed seed coat.