lecture 6 Flashcards
what tissue is the primary plant body made up of?
ground tissue
what does the ground tissue system consist of?
parenchyma, collenchyma, and sclerenchyma
where is the ground tissue found in the plant body?
the space between the epidermis and vasculature:
- cortex and pith in stems
- mesophyll in leaves
- cortex (and pith in monocots) in roots
what is the cortex?
region of primary ground tissue of a stem or root inside the epidermis, outside the vascular tissue
what is the pith?
region of primary ground tissue in the centre of a stem or root, within the vascular tissue
what is the mesophyll?
the ground tissue of a leaf, between the upper and lower epidermis and interspersed with the vascular bundles
when determining cell type, what would you look for?
- cell wall: primary, secondary wall, uniformity of thickness, pit patterns
- cells shape: isodiametric, polyhedral, elongated, branched, etc.
- status at maturity: dead or living
- cytoplasm: dense or vacuolated
- distribution throughout the plant: some types of cells are only found in one tissue (specialists), while others are found in many tissues (generalists)
how would you determine a parenchyma cell?
- cell wall: usually primary only, uniformly thick
- cell shape: relatively simple, isodiametric shape, intercellular air spaces
- status at maturity: living
- cytoplasm: can be dense or vacuolated depending on function (often highly vacuolated)
- distribution throughout the plant: found all over the plant (in both ground and vascular tissues)
what are the characteristics of parenchyma cells?
- most abundant and versatile cell type in plants
- everywhere in plant body
- relatively unspecialized
- often capable of de-differentiating and then re-differentiating into a new cell type (totipotent)
- often loosely packed with many intercellular air spaces
what is the function of storage parenchyma?
storage (accumulates starch, protein, water, oil, tannins, or crystals)
what is the function of secretory parenchyma?
secretion, often surrounding a duct within the tissue
what is the function of chlorenchyma and leaf mesophyll?
photosynthesis (have many chloroplasts)
what is the function of aerenchyma?
gas exchange
how would you determine a collenchyma cell?
- cell wall: primary only, non-uniformly thick
- cell shape: elongated with overlapping end walls, rounded in cross-section
- status at maturity: living
- cytoplasm: vacuolated
- distribution throughout plant: found in peripheral regions of stem and leaf (just beneath epidermis). often found external to a vascular bundle
what are the functions of collenchyma?
- protects vasculature (conducting cells)
- provides strength to developing organs (for herbaceous plants)
- flexible support