Chap 35-37 - Plants Flashcards
Meristem
Tissue that remains embryonic through a plant’s entire life.
Allows indeterminate growth.
Primary vs Secondary growth
Primary - growth in length.
Secondary - growth in thickness.
Vascular & Cork cambium
Lateral meristem tissue arranged in a ring.
Allows secondary growth.
Vascular arises from procambium, cork cambium arises from ground meristem.
Pneumatophores
Oxygen-absorbing roots that poke out of the ground - eg. in mangroves where the plant grows in oxygen-poor substrate.
Mycorrhizal associations
Connection between plant roots and mycelium; exchanges nutrients between the two.
Fibrous root system
Roots are arranged in a dense, shallow mat. Found in plants that are frequently grazed on by vertebrate herbivores.
Rhizomes vs Stolons vs Tubers
Rhizomes - horizontal shoots just below soil surface.
Stolons - “runner” stems above the soil, as in strawberries/mint.
Tubers - enlarged rhizomes or stolons (not roots).
Three main types of tissue in plants
Dermal (epidermis & periderm)
Vascular (xylem & phloem)
Ground tissue
Periderm
The ‘woody’ cells that replace epidermis. Produced by cork cambium, and contains a lot of lignin for strength.
Pith vs Cortex
In Eudicots:
Pith - ground tissue that is found internally of the vascular tissue.
Cortex - ground tissue that is between vascular and dermal tissue.
Major cell types in plants
(5)
Parenchyma cells - default, does everything.
Collenchyma cells - scaffold.
Sclerenchyma cells - woody (lignin)
Xylem & phloem cells
Parenchyma cells
A ‘normal’ plant cell:
- Thin, flexible primary cell wall; no secondary.
- Big central vacoule.
- Starch-storing amyloplasts.
- Able to divide and differentiate into other cell types.
Collenchyma cells
Quick, effective scaffolding in young plants:
- Elongated, with thickened but still flexible primary cell wall.
- Just beneath epidermis in young stems.
Sclerenchyma cells
Woody, basically:
- Big secondary cell wall with lignin for strength.
- Two types; boxy sclereids & elongated fibres.
Xylem cells
(two types)
Water and minerals from ground up:
- Dead at maturity.
- Tracheids; Elongated, with tapered end that overlaps with the next tracheid cell. Pits in the secondary cell wall in these overlapping regions allows water to move to the next cell.
- Vessel elements; Shorter & wider than tracheids, aligned end-to-end instead of tapered. Perforation plates with holes allows water movement between elements.
Phloem cells
(two types, kind of three?)
Sugars from leaves
- Alive at maturity!
- Made of sieve cells in gymnosperms & plants without seeds.
- In angiosperms, built from sieve-tube element cells. Sieve-tube elements have no nucleus/ribosomes/cytoskeleton.
- Elements connected through sieve plates with holes.
- A companion cell is next to each element, connected by lots of plasmodesmata. The companion’s nucleus/ribosomes serves the element cell.
Vascular cambian
- Layer that is single cell thick.
- Forms phloem on outside.
- Xylem on inside.
Root cap
“cap” of dead cells on the tip of a growing root. Made and constantly replenished by the meristem. Protects the meristem and softens the soil with mucous to help grow through it.
Pericycle
Outermost layer of cells of the stele (vascular bundle) in plant roots. Non-vascular, but controls the inputs/outputs of stuff into the vascular bundle.
Also propagates development of lateral roots.
Vascular rays
Radial lines of parenchyma cells that connect secondary xylem and phloem cells.
- Moves stuff between the vascular cells.
- Stores carbohydrates.
Dendrochronology (just for fun)
Science of analysing a tree’s growth rings.
Sapwood vs Heartwood
Sapwood - outer, younger layers of secondary xylem that transports xylem sap.
Heartwood - older, inner layers that no long transport xylem sap. Darker in colour.
Lenticels
Small areas with more space between cork cells.
Allows cells on the inside to exchange gases for respiration.
Pattern formation
Development of specific structures in specific locations - eg. dermal tissue on the outside, vascular on the inside.
