Ch. 25, Part One: Primary Stems

areas of a stem where one or more leaves attach

area, structure

dormant apical meristem has potential to form a new branch (shoot)

photosynthesis capabilities ability to form leaves no gaps in vascular cylinders in roots

area of stem between nodes

support of leaves transpiration/conduction of water, minerals, nutrients production of new shoot tissue photosynthesis

grows at tips houses apical meristem

stems produce leaves and lateral branches from shoot apical meristem no root cap - is protected by leaf primordia and bud scales

leaf and bud primordia the three primary meristems

forms new leaves

forms shoots, lateral stems, or flowers

periclinally, and others anticlinally

division is parallel with apical surface (upwards, adds layers)

division is perpendicular to the surface (side by side)

tunica-corpus

outermost cell layers divides anticlinally

adds surface to the stem

innermost cells divide mostly periclinally

adds bulk, "body" to the stem

give rise to primary tissues of main stem, new leaves, and lateral stems

tunica-corpus organization

outermost tunica layer (L1)

corpus (L3)

1-2 cells thick covers entire stem

houses stomata photosynthesis

filler tissue in stem

parenchyma collenchyma sclerenchyma

almost continuous vascular cylinder, narrow interfascicular regions spread out vascular cylinder, wide interfascicular regions scattered vascular bundles

Tilia (American liden)

Medicago, Sambucus, Ranuculus (burclover, elderberry, buttercup)

• Medicago is pictured.

Zea mays (maize)

ground tissue in between vascular bundles within the same radius

cambium in between the phloem and xylem

between, within (between xylem and phloem)

retain cambium capable of secondary growth

no cambium not capable of secondary growth

zone at or near soil level vascular tissue in roots transitions into different stele in their stems

True

Added support Different functions (photosynthesis needs, creation of leaves, branch creation, etc)

one or more vascular bundles cross the cortex and enter the leaf attatched to the node

wide spaces above leaf traces, where the diverge toward the leaf

stems modified for additional needs

a horizontal plant stem with shoots above and roots below serving as a reproductive structure

horizontal aboveground stems

strawberries Bermuda grass

specialized storage stem that forms at tips of rhizomes/stolons

underground food storage stems shaped like bulbs

aboveground food storage

kohlrabi

modded branches from axils of leaves

roses

modded stems that resemble foliage leaves

asparagus, prickly pear cactus, butcher's broom

makes a symbiotic relationship with ants provides a home to the ants in return, the ants protect the plant