STRUCTURE AND SEASONAL DEVELOPMENT OF SECONDARY PHLOEM IN PINACEAE
STRUCTURE AND SEASONAL DEVELOPMENT OF SECONDARY PHLOEM IN PINACEAE
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DOI：
10.1086/336674
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发表时间：
1973-01-01
影响因子：
--
通讯作者：
EVERT, RF
中科院分区：
文献类型：
--
作者：
ALFIERI, FJ;EVERT, RF
落叶松(Larix laricina(Du Roi)Koch)、冷杉(Abies balsamea(L)Mill)和欧洲云杉(Picea Mariana(Mill.)BSP。关于某一年的生长增量，除了最后形成的筛细胞(一至四层)外，所有的筛细胞在它们从形成层产生的同一季节停止运作。最后形成的筛子细胞越冬，并在下一个生长季保持功能。4月底，形成层外缘的未分化细胞开始分化为筛状细胞。大约一周后，形成层活动(细胞分裂)开始，所有的早期韧皮部在新的木质部分化开始之前产生，也就是说，在木质部分化开始之前，到5月中旬，在L.Laricina和P.Mariana中，到5月底，大多数筛子细胞到9月初分化，9月底开始停止功能，越冬筛子细胞上形成最终的老茧，并继续筛选本季节早期韧皮部的细胞。到12月初，除了最后形成的筛子细胞(即那些将在正常状态下越冬的筛子细胞)外，所有的筛子细胞都没有内容物。韧皮部分化先于木质部分化约1个月。木质部和韧皮部分化和形成层活动在9月初大致同时停止。树脂细胞是木香非传导性韧皮部的特征，由具有完整核的壁和原生质体组成。
Functional sieve cells are present for the entire year in the secondary phloem of Larix laricina (Du Roi) K. Koch, Abies balsamea (L) Mill, and Picea mariana (Mill.) BSP. With regard to a given year's growth increment, all but the last-formed sieve cells (one to four layers) cease functioning in the same season in which they are derived from the cambium. The last-formed sieve cells overwinter and remain functional throughout the next growing season. Toward the end of April, undifferentiated cells in the outer margin of the cambial zone begin to differentiate into sieve cells. About a week later, cambial activity (cell division) commences All early phloem is produced before new xylem differentiation begins, that is, by mid-May in A. balsamea and by the end of May in L. laricina and P. mariana Most sieve cells are differentiated by early September Cessation of function begins by the end of September with the formation of definitive callose on the overwintering sieve cells and continues to sieve cells of the current season's early phloem. By early December, all but the last-formed sieve cells (i e., those which will overwinter in a functional state) are devoid of contents. Phloem differentiation precedes xylem differentiation by approximately 1 month. Xylem and phloem differentiation and cambial activity cease at approximately the same time in early September. Resin cells that are characteristic of the nonconducting phloem in A. balsamea consist of walls and protoplasts with intact nuclei.