The end walls of sieve-tube elements in the phloem have 4-6 specialized sieve areas which together form compound sieve plates.
韧皮部中筛管分子的端壁是由4—6个梯状排列的筛域组成的复筛板。
The tracheid and sieve tube elements are all differentiated from the procambia in the center of the haustoria, and the former occurs prior to the latter.
吸器中管胞和筛管都是从吸器中央具有原形成层特性的细胞分化的，管胞的分化先于筛管，或同时进行。
The tracheid and sieve tube elements are all differentiated from the procambia in the center of the haustoria, and the former occurs prior to the latter.
吸器中管胞和筛管都是从吸器中央具有原形成层特性的细胞分化的，管胞的分化先于筛管，或同时进行。
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