The products of the stems primary meristems become stem tissues

The shoot apical meristem, like the root apical meristem, forms three primary meristems: the protoderm, the ground meristem, and the procambium. These primary meristems, in turn, give rise to the three tissue systems. The shoot apical meristem also repetitively lays down the beginnings of leaves and lateral buds. Leaves arise from bulges called leaf primordia, which form as cells divide on the sides of shoot apical meristems (see Figure 35.13). Bud primordia form at the bases of the leaf primordia. The growing stem has no protective structure analogous to the root cap, but the leaf primordia can act as a protective covering for the shoot apical meristem.

The plumbing of angiosperm stems differs from that of roots. In a root, the vascular tissue lies deep in the interior, with the xylem at or near the very center

35.18 Vascular Bundles in Stems (a) In eudicot stems,the vascular bundles are arranged in a cylinder, with the pith in the center and the cortex outside the cylinder. (b) A scattered arrangement of vascular bundles is typical of monocot stems.

(a) Eudicot

(a) Eudicot

Eudicot Stem

Phloem

Vascular cambium

Xylem

The vascular tissues in stems are organized into bundles.

Eudicot vascular bundle Sieve tube members Companion cells

The vascular tissues in stems are organized into bundles.

Phloem

Vascular cambium

Xylem

Eudicot vascular bundle Sieve tube members Companion cells

Monocot Vascular Bundles

Phloem

Xylem

Air space

Monocot vascular bundle

Phloem

Xylem

Air space

Monocot vascular bundle

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