Plant Biology: Topic 9.3: Plant Growth Flashcards
Define meristems
Meristems are tissues in a plant consisting of undifferentiated cells capable of indeterminate growth
They are analagous to totipotent stem cells in animals, except that they have specific regions of growth and development
Meristematic tissue can allow plants to regrow structures or even form entirely new plants (vegetative propagation)
Types of meristem and their function
Meristematic tissue can be divided into apical meristems and lateral meristems:
Apical meristems occur at shoot and root tips and are responsible for primary growth (i.e. plant lengthening)
Lateral meristems occur at the cambium and are responsible for secondary growth (i.e. plant widening / thickening)
Apical meristems give rise to new leaves and flowers, while lateral meristems are responsible for the production of bark
What is responsible for growth at apical meristems
Growth at these regions is due to a combination of cell enlargement and repeated cell division (mitosis and cytokinesis)
Differentiation of the dividing meristem gives rise to a variety of stem tissues and structures – including leaves and flowers
What is responsible for growth at apical meristems
Growth at these regions is due to a combination of cell enlargement and repeated cell division (mitosis and cytokinesis)
Differentiation of the dividing meristem gives rise to a variety of stem tissues and structures – including leaves and flowers
What are axillary buds?
Axillary buds are shoots which are inactive and left behind as regions of meristems at the junction or node of the stem when the shoot apical meristem grows and forms leaves.
These axillary (lateral) buds have the potential to form new branching shoots, complete with leaves and flowers
What is auxin and how does it carry out its function
The growth of the stem and the formation of new nodes is controlled by plant hormones released from the shoot apex
One of the main groups of plant hormones involved in shoot and root growth are auxins (e.g. indole-3-acetic acid / IAA)
When auxins are produced by the shoot apical meristem, it promotes growth in the shoot apex via cell elongation and division
Discuss role of auxin in apical dominance
The production of auxins additionally prevents growth in lateral (axillary) buds, a condition known as apical dominance
Apical dominance ensures that a plant will use its energy to grow up towards the light in order to outcompete other plants
As the distance between the terminal bud and axillary bud increases, the inhibition of the axillary bud by auxin diminishes
Different species of plants will show different levels of apical dominance
