Shane Michael W, McCully Margaret E, Lambers Hans
School of Plant Biology, Faculty of Natural and Agricultural Sciences, University of Western Australia, Crawley, WA 6009, Australia.
J Exp Bot. 2004 May;55(399):1033-44. doi: 10.1093/jxb/erh111. Epub 2004 Mar 26.
Storage of phosphorus (P) in stem tissue is important in Mediterranean Proteaceae, because proteoid root growth and P uptake is greatest during winter, whereas shoot growth occurs mostly in summer. This has prompted the present investigation of the P distribution amongst roots, stems, and leaves of Hakea prostrata R.Br. (Proteaceae) when grown in nutrient solutions at ten P-supply rates. Glasshouse experiments were carried out during both winter and summer months. For plants grown in the low-P range (0, 0.3, 1.2, 3.0, or 6.0 micromol d(-1)) the root [P] was > stem and leaf [P]. In contrast, leaf [P] > stem and root [P] for plants grown in the high-P range (6.0, 30, 60, 150, or 300 micromol P d(-1)). At the highest P-supply rates, the capacity for P storage in stems and roots appears to have been exceeded, and leaf [P] thereafter increased dramatically to approximately 10 mg P g(-1) dry mass. This high leaf [P] was coincident with foliar symptoms of P toxicity which were similar to those described for many other species, including non-Proteaceae. The published values (tissue [P]) at which P toxicity occurs in a range of species are summarized. X-ray microanalysis of frozen, full-hydrated leaves revealed that the [P] in vacuoles of epidermal, palisade and bundle-sheath cells were in the mM range when plants were grown at low P-supply, even though very low leaf [P] was measured in bulk leaf samples. At higher P-supply rates, P accumulated in vacuoles of palisade cells which were associated with decreased photosynthetic rates.
在地中海地区的山龙眼科植物中，磷（P）在茎组织中的储存很重要，因为在冬季，排根的生长和磷的吸收最为旺盛，而地上部分的生长主要发生在夏季。这促使我们开展了本次研究，探究了在10种磷供应水平的营养液中生长的平卧哈克木（山龙眼科）根、茎和叶中的磷分布情况。温室实验在冬季和夏季都进行了。对于在低磷水平（0、0.3、1.2、3.0或6.0微摩尔·天⁻¹）下生长的植物，根中的磷含量大于茎和叶中的磷含量。相比之下，在高磷水平（6.0、30、60、150或300微摩尔·天⁻¹）下生长的植物，叶中的磷含量大于茎和根中的磷含量。在最高的磷供应水平下，茎和根中储存磷的能力似乎已被超过，此后叶中的磷含量急剧增加至约10毫克磷·克⁻¹干重。这种高叶磷含量与磷中毒的叶片症状同时出现，这些症状与许多其他物种（包括非山龙眼科植物）所描述的症状相似。本文总结了一系列物种中发生磷中毒时的已发表值（组织磷含量）。对冷冻、完全水合的叶片进行的X射线微分析表明，当植物在低磷供应条件下生长时，表皮、栅栏和维管束鞘细胞液泡中的磷含量处于毫摩尔范围内，尽管在整片叶片样本中测得的叶磷含量非常低。在较高的磷供应水平下，磷在栅栏细胞的液泡中积累，这与光合速率降低有关。
