Growth in Plants - Biology 35

Biology 35 - Plant Science

Totipotent cells

can grow into an entire organism

multipotent cells

only grows into one type of associated cell type

pluripotent cells

Can grow into any type of cell but not an entire organism

Meristem

tissue in plants containing undifferentiated cells; found where plant growth occurs

\
* shoots = apical meristems (primary growth: lengthening)
* roots = root apical meristems (primary growth: lengthening)
* cambium = lateral meristems (secondary growth: widening)

Indeterminate Growth

* cells continue to divide forever
* trees never stop growing
* most plants have indeterminate growth, occurring at meristems

Mitosis

* replication of the DNA in a cell so the cell can divide into 2 daughter cells

Shoot Apex (shoot meristem)

* provides cells for growth of stems, leaves, flowers
* after cell division, one cell remains in the meristem while other differentiates

Hormones

* chemical messenger released in one part of an organism to have an effect in another part of the organism

Auxins

* plant hormones produced in apical meristem
* initiate growth or roots
* development of fruits
* regulate development of leaves
* inhibits growth of axillary buds

Apical Dominance

the growth of the main stem is prioritized over the growth of lateral branches. This is due to the production of auxin hormone in the apical meristem, which inhibits the growth of lateral buds. As a result, the plant grows taller and has a more centralized structure.

Phototropism

direction of stem growth influenced by light

* light absorbed by photoreceptors by phototropin
* specific wavelength causes phototropin to have conformation change
* new shape binds to receptors in cell that control transcription of specific genes that affect the transport of auxin

Gravitropism

direction of stem growth influence by gravity

* auxin inhibits elongation in roots (opposite to shoot)

Auxin Efflux Pumps

* Auxin efflux pumps can set up concentration gradients within tissues – changing the distribution of auxin within the plant


* Auxin efflux pumps can set up concentration gradients within tissues – changing the distribution of auxin within the plant
* These pumps can control the direction of plant growth by determining which regions of plant tissue have high auxin levels
* Auxin efflux pumps can change position within the membrane (due to fluidity) and be activated by various factors