氮磷供给对两种马先蒿根系形态建成的影响

Effects of Nitrogen and Phosphorus Supply on Root Morphology of Two Pedicularis Species

采用溶液培养法在无寄主伴生的条件下对三色马先蒿(Pedicularis tricolor)和大王马先蒿(P.rex)进行培养,分别分析了不同氮磷供给水平(标准Long Ashton营养液、缺氮、缺磷、2倍氮、2倍磷)及不同氮素形态(硝态氮和铵态氮)对两种马先蒿根系形态建成的影响。结果表明:1)氮磷供给水平对两种马先蒿的主根长、侧根长、侧根数量以及吸器发生的影响存在种间差异,缺氮和缺磷均能促进三色马先蒿主根和侧根的伸长生长及吸器的产生,而相同条件下大王马先蒿根系生长受到抑制,且没有吸器产生;2)氮素形态对两种马先蒿根系形态建成及生长发育存在影响:1倍硝态氮的处理中,三色马先蒿的根系生长最好,生物量积累最多,相同条件下大王马先蒿根系生长和生物量积累与标准营养液处理无差异,而仅供应铵态氮对二者的生长不利。此外,发现三色马先蒿的吸器产生不需要机械刺激。初步推测,两种马先蒿的吸器产生机制或进程存在差异,氮和磷可能参与了吸器发生过程的调控。

In this study, we used hydroponics to cultivate the root hemiparasites, Pedicularis tricolor and P. rex, in the absence of their host plants. The direct effects of nitrogen （N） and phosphorus （P） levels and different nitrogen forms on root architecture of the two species were tested in two experiments using nutrient solutions modified from the standard Long Ashton formula. In Experiment 1, solutions were used which either lacked N or P, or contained doub le the standard concentrations of N or P. In Experiment 2, different forms of N （NO3--N and NH4^＋-N） were sup plied. Obvious changes were observed in root morphology of both Pedicularis species in response to different levels of N and P supplied. However, the two Pedicularis species showed different responses to N and P deficiency. In P. tri color, both N and P deficiency promoted elongation of the main and lateral roots, as well as the formation of hausto ria. In contrast, root development in P. rex was significantly inhibited by a lack of either N or P. No haustoria were observed in roots of P. rex in any of these treatments. Varying the nitrogen source had a strong effect on root morphol ogy and growth of both Pedicularis species, with NO3-N promoting better root development and biomass accumulation, relative to NH4 ^＋-N. In addition, we observed that P. tricolor produced many haustoria without the need of me chanical stimulus. In light of these findings, we propose that mechanisms of haustorium formation may be significant ly different between these two species, and that N and P may be involved in the regulation of haustorium formation in both species.