Plant Tissues: Ground
Ground Tissues consist primarily of thin-walled parenchyma cells. Other ground tissue is composed of collenchyma cells and sclerenchyma cells
parenchyma cells
most common type of plant cell
large vacuoles, thin walls, and are initially(briefly) more or less spherical
living protoplasts push up against each other shortly after being produced and produce other shapes, ending up with 11 to 17 sides.
function in storage of food and water, photosynthesis, and secretion
most abundant cells of primary tissue and may also occur in a much lesser extent insecondary tissues.
most only have primary walls(walls laid down while the cells are still maturing)
less specialized than other plant cells, although many variations occur with special functions ( nectar and resin secretion or storage of latex, proteins, and metabolic waste).
functional nuclei and are capable of dividing
remain alive after maturation; (100 years old in cacti)
some contain chloroplasts (especially in leaves and other outer plant parts)- photosynthetic parenchyma tissue called chlorenchyma
collenchyma cells
have living protoplasts and may live for many years
usually a little longer than wide
have walls that vary in thickness
provide support for plant organs, allowing them to bend without breaking(flexible)
often form strands or continuous cylinders beneath the epidermis of stems or stalks and along the veins in leaves.
provide much support for stems in primary plant body.
example: celery strings.
sclerenchyma cells
tough, thick walls.
usually lack living protoplasts at maturity (unlike collenchyma and parenchyma)
secondary cell walls impregnated with lignin
lignin -highly branched polymer that makes cell walls more rigid. cell walls containing this are considered lignified. Common in walls of plant cells that have a structural or mechanical function. Could be in primary walls as well.
two types: fibers and sclereids; both serve to strengthen the tissues in which they occur
fibers - long, slender cells that are usually grouped together in strands.
sclereids- variable in shape but often branched.May occur singly or in groups; they are not elongated, but may have many different forms (one is a star). Found in hard seed coats. Cause gritty texture of pair.
BIOL 1105/1106 Virginia Polytechnic Institute and State University