SWORDS INTO PLOWSHARES - NICOTIANA-SYLVESTRIS DOES NOT USE NICOTINE AS A NITROGEN-SOURCE UNDER NITROGEN-LIMITED GROWTH
SWORDS INTO PLOWSHARES - NICOTIANA-SYLVESTRIS DOES NOT USE NICOTINE AS A NITROGEN-SOURCE UNDER NITROGEN-LIMITED GROWTH
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DOI：
10.1007/bf00324228
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发表时间：
1994-08-01
期刊：
影响因子：
2.7
通讯作者：
OHNMEISS, TE
中科院分区：
文献类型：
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作者：
BALDWIN, IT;OHNMEISS, TE
植物是否能够回收其在化学防御中的资源投资，是资源可用性理论中“移动-固定”代谢物二分法的核心。代谢物周转的生化措施已被用来估计这一特点，但他们没有解决资源回收的生态问题。许多研究发现，许多烟草属物种，通常产生氮密集型防御代谢产物尼古丁，可以快速吸收和代谢外源施用的尼古丁从水培溶液。然而，Baldwin等人（1994）在脉冲追踪实验中使用（NO3）-N-15作为N. splvestris。考虑到代谢尼古丁的能力的存在，我们问（1）是否N。在氮限制条件下，樟子松能代谢外源供给的烟碱并维持生长;（2）叶片损伤是否改变植物利用烟碱作为氮源的能力。我们在水培中给植物喂入足够的尼古丁，使它们的氮库在喂入尼古丁时增加70%;在28-35天的6-10次连续收获中，我们测量了根、叶和茎的生物量，以及这些植物部分的总氮库以及尼古丁库，在未受损的尼古丁饲喂植物和对照植物中，以及最后在单独的实验中，在尼古丁饲喂的受损和未受损植物中，对这些植物部分的去甲尼古丁和麦斯明进行了测定。尼古丁喂养增加了1.2倍的尼古丁库，这是不足以显着增加总氮库在实验结束。在实验期间，给予尼古丁的植物将其获得的尼古丁库快速脱甲基化为去甲尼古丁，但对生物碱库的处理并不超过麦斯明。叶片损伤显着增加了尼古丁库，但没有显着改变外源获得的尼古丁的处理。我们的结论是N.因此，即使在氮限制生长下，樟子松也不能回收投入尼古丁的氮，外源引入的尼古丁的快速代谢可能是解毒途径，并且这些植物就其尼古丁库而言是稳态的。
Whether or not a plant can recover its investment of resources in a chemical defense is central to the ''mobile-immobile'' metabolite dichotomy of the resource availability theory. Biochemical measures of metabolite turnover have been used to estimate this trait, but they do not address the ecological question of resource recovery. Numerous studies have found that many Nicotiana species, which normally produce the nitrogen-intensive defense metabolite, nicotine, can rapidly take up and metabolize exogenously administered nicotine from hydroponic solutions. However, Baldwin et al. (1994) found no evidence for turnover of endogenously produced nicotine in pulse-chase experiments using (NO3)-N-15 as the biosynthetic precursor in N. splvestris. Given that the capacity to metabolize nicotine exists, we asked (1) whether N. sylvestris could metabolize exogenously fed nicotine and sustain growth under nitrogen-limited conditions and (2) whether leaf damage alters the plants' ability to use nicotine as a nitrogen source. We fed plants with sufficient nicotine in hydroponic culture to increase their nitrogen pools by 70% at the time of nicotine feeding; in 6-10 consecutive harvests over 28-35 days, we measured the biomass of roots, leaves and stems, and the total nitrogen pools of these plant parts as well as the pools of nicotine, nornicotine and myosmine of these plant parts in undamaged nicotine-fed and control plants and finally, in a separate experiment, in nicotine-fed damaged and undamaged plants. Nicotine feeding increased nicotine pools by 1.2 times, which was not sufficient to significantly increase total nitrogen pools at the end of the experiment. Nicotine-fed plants rapidly demethylated their acquired nicotine pools to nornicotine, but did not process the alkaloid pool further than myosmine over the duration of the experiment. Leaf damage significantly increased the nicotine pool, but did not significantly alter the processing of the exogenously acquired nicotine. We conclude that N. sylvestris is does not recover the nitrogen invested in nicotine even under nitrogen-limited growth, that the rapid metabolism of exogenously introduced nicotine likely a detoxification pathway, and that these plants are homeostatic with regard to their nicotine pools.