9.3 - Growth in Plants Flashcards
Undifferentiated cells in the meristems of plants allow indeterminate growth
1) Define indeterminate growth and totipotent
2) State that most plants have indeterminate growth and have totipotent cells
3) Define meristems
4) Compare apical and lateral meristems
Meristems in all plants consist of undifferentiated cells that generate new cells for plant growth
Plant growth = indeterminate which means they can grow indefinelty
Many plant cells even fully differentiated cells can generate whole new plants containing cells that are totipotent. The characteristics sets plants apart from most animals
Meristems are areas where growth occurs and are composed of undifferentiated cells undergoing active cell division - apical meristems at the tips of roots and stems (primary growth) - lateral meristems (secondary = diameter and thickness)
Dicots = apical and lateral meristems
Mitosis and cell division in the shoot apex provide cells needed for extension of the stem and development of leaves
1) outline the role of mitosis in the growth of stem and leaves while maintaining a meristem
Cells in the meristems undergo mitosis rapidly to produce new cells and growth in plant - root meristems = responsible for growth and extension of the root
Shoot meristems = creates cells responsible for shoot growth and also creates cells that will develop into flowers and leaves
Apical meristems = create additional meristems including protoderm, procambium and group meristem
Leaf primordia forms leaves
Plant hormones control growth in the shoot apex
1) State the generic function of plant hormones
2) Outline how auxin concentrations regulate plant growth in the root and stem
3) Outline the role of auxin in apical dominance
Hormones are chemical messengers produced and released by one part of an organism that has effect on another location.
Auxin : promotion of stem elongation and growth; promotion of cell division and promotion of lateral bud dormancy : shoot apical meristem
Cytokinins : promotion of cell division (with auxins), promotion of lateral bud formation : root apical meristems
Plant shoots respond to the environment by tropism
1) State two external factors that control the growth of roots and shoots
2) Define tropism, phototropism, gravitropism
tropism is a growth towards or away from an external stimulus - light gravity or chemicals
1) Gravitropism growth response to gravity, phototropism towards light, generally shoots grow towards the light and roots grow away from the light
phototropism is essential for plants to make sure they grow towards the sunlight
Auxin efflux pumps can set up concentration gradients of auxin in plant tissue
1) Outline how PIN-transport proteins can direct direction of auxin flow
2) Explain how auxin conc allows for phototropism in the stem
3) Explain how auxin conc allow for gravitropism in the root
Auxin = plant hormones that promote positive phototropism in plants - only work on plant cells with auxin receptors and increase flexibility of plant cells in developing shoots - enables cell elongation on the side of the shoot necessary to cause growth towards light
if the amount of sunlight is greater on one side of the plant - high conc of auxins cause cells on the shaded side of the cell to swell and elongate. When auxin binds to receptor in nucleus, activates a proton pump which moves H ions into spaces in the cell wall decreasing the pH - results in breaking of hydrogen bonds between cellulose fibres - swelling and elongation - with start to curve due to uneven plant growth
Auxin influences cell growth rates by changing the pattern of gene expression
1) State that auxin influences cell growth rated by changing gene expression
Auxin = plant hormone and influences cell growth by changing pattern of gene expression with a plant’s cells. method of action different in shoots and roots as gene pathways are activated in each tissue - Auxin moved to side of stem with least light causing cell alongate on dark side grow faster
Micropropagation of plants using tissue from the shoot apex, nutrient agar gells and growth hormones
1) Define micropropagation
2) Outline how changing auxin and cytokinin ratios can lead to development of roots or shoots from the same explant tissue.
Micropropagation is rapid multiplication of a selected plant using in in vitro culture techniques - propagation of selected plant through micropropagation would be useful for raising plantation using apical and nodal segment - best for micropropagation and mostly result in true to type plants : segments upon the subsequent subcultures result in normal number of multiple shoots - multiple shoots on elongation allowed to root in vitro.
Meristem culture : meristem and a few subtending leaf primordial are places into a suitable growing media
Callus culture: a callus is mass of undifferentiated cells - when a living tissue is placed in an artificial growing medium with other conditions callus is formed
Suspension culture : cells and or groups of cells dispersed and growing in an aerated liquid culture medium
Embryo culture : embryo is excised and placed into a culture medium with proper nutrient
Protoplast culture : plant cell isolated with the help of wall degrading enymes and growth in cuitable culture medium
Use of micropropagation for rapid bulking up of new varieties, production of virus-free strains of existing varieties and propagation of orchids and other rare species
1) Outline three roles of micropropagation of plant species
Micropropagation can be used to produce disease free plants
high fecundity rate - producing thousand of propagules while conventional techniques may only produce fraction of the number
only viable method of regenerating genetically modified cells
useful in multiplying plants which produce seeds in uneconomical amount or when plants are sterile and do not produce viable seeds
produce more robust plants leading to accelerated growth compared to other methods
great number of plants can be produced per square meter and store longer and in smaller area
