Thorn Alexandra M, Orians Colin M
Department of Biology, Tufts University, 163 Packard Avenue, Medford, MA 02155, USA.
Funct Plant Biol. 2011 Nov;38(11):879-887. doi: 10.1071/FP11141.
Root conductance increases under high nitrate conditions. This plasticity might increase water and nutrient transport between parallel xylem pathways, but restrictions to lateral flow - called sectoriality - are expected to limit this crossover. We simulated the effects of a high nitrate patch on root conductance, water uptake and inter-sector water transport, then empirically tested whether a high nitrate patch affects water uptake and nitrogen distribution (applied 15N as 14NH415NO3 to half the root system) within the crowns of split-root hydroponic basil (Ocimum basilicum L.). Simulations showed that at low sectoriality, the proportion of water taken up in a patch scales with the relative change in root resistance and that this fraction decreases with increasing tangential resistance. The effect of sectoriality decreased when a higher background root resistance was assumed. Empirically, water flow through excised basil roots was 1.4 times higher in the high nitrate than the no nitrate solution. In split-root basil, a nitrate patch resulted in a marginally significant increase in the proportion of water taken up from the patch and water uptake patterns significantly predicted the distribution of 15N. Our results suggest that root conductance can mediate nitrogen allocation between sectors, a previously unexplored benefit.
在高硝酸盐条件下，根导度会增加。这种可塑性可能会增加平行木质部途径之间的水分和养分运输，但横向流动的限制——即所谓的扇形性——预计会限制这种交叉。我们模拟了高硝酸盐斑块对根导度、水分吸收和扇形间水分运输的影响，然后通过实验测试了高硝酸盐斑块是否会影响分根水培罗勒（Ocimum basilicum L.）冠层内的水分吸收和氮分布（将15N以14NH415NO3的形式施用于一半根系）。模拟结果表明，在低扇形性情况下，斑块中吸收的水分比例与根阻力的相对变化成比例，并且随着切向阻力的增加，这一比例会降低。当假设背景根阻力较高时，扇形性的影响会减弱。通过实验发现，在高硝酸盐溶液中，切下的罗勒根的水流比在无硝酸盐溶液中高1.4倍。在分根罗勒中，硝酸盐斑块导致从斑块中吸收的水分比例略有显著增加，并且水分吸收模式显著预测了15N的分布。我们的结果表明，根导度可以介导扇形间的氮分配，这是一个以前未被探索的益处。
