Ageeva M V, Petrovská B, Kieft H, Sal'nikov V V, Snegireva A V, van Dam J E G, van Veenendaal W L H, Emons A M C, Gorshkova T A, van Lammeren A A M
Laboratory of Plant Cell Biology, Wageningen University, The Netherlands.
Planta. 2005 Nov;222(4):565-74. doi: 10.1007/s00425-005-1536-2. Epub 2005 Nov 4.
Flax (Linum usitatissimum L.) phloem fibers elongate considerably during their development and intrude between existing cells. We questioned whether fiber elongation is caused by cell tip growth or intercalary growth. Cells with tip growth are characterized by having two specific zones of cytoplasm in the cell tip, one with vesicles and no large organelles at the very tip and one with various organelles amongst others longitudinally arranged cortical microtubules in the subapex. Such zones were not observed in elongating flax fibers. Instead, organelles moved into the very tip region, and cortical microtubules showed transversal and helical configurations as known for cells growing in intercalary way. In addition, pulse-chase experiments with Calcofluor White resulted in a spotted fluorescence in the cell wall all over the length of the fiber. Therefore, it is concluded that fiber elongation is not achieved by tip growth but by intercalary growth. The intrusively growing fiber is a coenocytic cell that has no plasmodesmata, making the fibers a symplastically isolated domain within the stem.
亚麻（Linum usitatissimum L.）韧皮纤维在其发育过程中会显著伸长，并侵入到现有细胞之间。我们质疑纤维伸长是由细胞顶端生长还是居间生长引起的。具有顶端生长的细胞的特征是在细胞顶端有两个特定的细胞质区域，一个在顶端非常靠近的位置，有小泡但没有大的细胞器，另一个在亚顶端有各种细胞器，其中包括纵向排列的皮层微管。在伸长的亚麻纤维中未观察到这样的区域。相反，细胞器移动到了非常靠近顶端的区域，并且皮层微管呈现出居间生长细胞所具有的横向和螺旋状构型。此外，用荧光增白剂进行的脉冲追踪实验在纤维全长的细胞壁上产生了点状荧光。因此，得出的结论是，纤维伸长不是通过顶端生长实现的，而是通过居间生长实现的。侵入性生长的纤维是一个无胞间连丝的多核细胞，这使得纤维成为茎内一个共质体隔离的区域。
