Late * primary phloem. The metaphloem completes its elongation after the surrounding tissues have ceased elongating and therefore, unlike the * protophloem, is not obliterated. However, in plants exhibiting secondary growth, the growth of the secondary phloem often results in obliteration of the metaphloem. Unlike those in the protophloem, these obliterated cells do not usually differentiate into fibres, although they may undergo sclerification. The * sieve elements of the metaphloem are usually wider and longer than those of the protophloem, and their * sieve plates are usually more distinct. Compare metaxylem. |
