Kropf D L, Harold F M
J Bacteriol. 1982 Jul;151(1):429-37. doi: 10.1128/jb.151.1.429-437.1982.
Previous work in this laboratory demonstrated that the rhizoids of Blastocladiella emersonii grow chemotropically toward a source of Pi and thus provided preliminary evidence that, in addition to serving as a holdfast, the rhizoids absorb nutrients. To further examine the role of the rhizoids in nutrient uptake, we devised a technique to introduce a barrier between the rhizoids and the thallus to that these cell compartments could be studied independently. Cells were grown on polycarbonate membrane filters in such a way that all of the thalli were on one side of the filter and essentially all of the rhizoids were on the opposite side. Nutrient uptake into the rhizoids and the thallus was measured by floating the filters bearing cells on radioactive medium so that only one side of the filter contacted the label. Mineral oil was used to block the diffusion of the label through the unfilled pores in the filter. This technique permitted us to establish clearly that the rhizoids absorb all seven of the nutrients tested. In addition, we found that some nutrients, specifically Pi and amino acids, appeared to be preferentially taken up via the rhizoids, whereas K+, Rb+, and Ca2+ entered the thallus and rhizoids equally. Cells grown in the presence of the microtubule synthesis inhibitors nocodazole and carbendazim elaborated only a stunted rhizoid system, so we examined their ability to accumulate the two classes of compounds. As expected, these cells were severely inhibited in Pi and amino acid uptake but retained normal uptake of K+, Rb+, and Ca2+.
本实验室之前的研究表明，艾氏布氏藻的假根会向磷酸盐源进行趋化生长，从而初步证明，假根除了起到固着作用外，还能吸收养分。为了进一步研究假根在养分吸收中的作用，我们设计了一种技术，在假根和叶状体之间设置一道屏障，以便能够独立研究这些细胞区室。细胞在聚碳酸酯膜滤器上生长，使得所有叶状体都在滤器的一侧，而基本上所有假根都在另一侧。通过将带有细胞的滤器漂浮在放射性培养基上来测量养分向假根和叶状体中的吸收情况，这样滤器只有一侧与标记物接触。使用矿物油来阻止标记物通过滤器中未填充的孔隙扩散。这项技术使我们能够明确证实，假根吸收了所测试的全部七种养分。此外，我们发现一些养分，特别是磷酸盐和氨基酸，似乎优先通过假根吸收，而钾离子、铷离子和钙离子则以相同的程度进入叶状体和假根。在微管合成抑制剂诺考达唑和多菌灵存在的情况下生长的细胞，只形成了发育不良的假根系统，因此我们研究了它们积累这两类化合物的能力。正如预期的那样，这些细胞在磷酸盐和氨基酸吸收方面受到严重抑制，但对钾离子、铷离子和钙离子的吸收保持正常。
