stem structure - external/internal
- heartwood - inside, nonfunctional part of stem
- sealed off w/ lignin
- only for structure
- sapwood - functional, still acts as transport
- external form - primordia (bulges) develops into leaves, shoots, flowers
- phyllotaxy - leaves arranged 137.5 degrees apart (golden mean)
- node - region where leaf attaches
- internode - area of stem between 2 nodes
- sessile leaf - leaf lacking the petiole (stalk)
- axillary bud at every axil (between petiole/stem)
- scars - mark where stems branch off
- lenticels - pores for gas exchange
- internal form - apical meristem at stem’s tip produces primary meristems
- protoderm >> epidermis
- ground meristem >> parenchyma cells (pith in center, cortex away from center)
- procambium >> primary xylem/phloem
- trace - strand of xylem/phloem branching off from the main clinder >> enters developing leaf, flower, shoot >> produces gap
- periderm - cork cambium, cork, phelloderm found between epidermis and collenchyma
- outer bark - made of cork tissue
modified stems - most grow erect
- bulbs - swollen underground stems w/ adventitious roots (ex. onion)
- corms - similar to bulbs but w/ no fleshy leaves
- rhizomes - horizontal stems growing underground
- runners/stolons - similar to rhizomes, but grows on the surface
- tubers - swollen tips of stolons (ex. potatoes)
- tendrils - twins around supports (ex. climbing plants like grapes)
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