Lecture 1: Overview of Plant Life and Plant Systematics Flashcards
Common perception that plants have/are:
-Simple structure
-Inert/passive
-Inability to sense environment
-Unable to react suddenly
What is the reality to this misconception?
Plants have/are:
-Complex structures
-Able of smelling, talking, communicating
-Able of touching and moving
-Capable of defending themselves
-Capable of kin recognition
Plants’ ability to respond to attacks
-Plants are stationary, rooted in one place: they can collect local information and respond by altering their defence and distributing valuable sources.
-Plants have modular organs (components can be taken apart and recombined in different ways): increases their ability to multitask as information can be derived from leaves and roots.
-Plants can tolerate attacks and tissue loss: they have the ability to reallocate resources and regrowth.
Modular structure of leaf (structure and function)
(Top to bottom)
-Apical meristem: AKA “growing tip”, an undifferentiated meristematic tissue. Main function is to trigger the growth of new cells in young seedlings at the tips of roots and shoots of forming buds.
-Node: Stems that sprout from the main stem. Nodes are the points on a stem where the buds, leaves, and branching twigs originate. They are crucial spots on the plant where important healing, structural support, and biological processes take place.
-Internode (stem): The stem between nodes.
-Leaf: Primary function is to conduct photosynthesis, conduct transpiration (movement of water through plant), prevent water loss, mechanical defence (spikes, scents, etc.)
-Axillary bud:
Axillary buds have the ability to produce new shoots to promote the growth of the plant and may be specialized by giving rise to either vegetative shoots or reproductive shoots. Axillary buds may also either remain inactive for some time or generate a shoot immediately after their formation.
Plant communication to external attack
1.) Intraspecific signalling (within one plant): response to clipping, herbivory, infection, etc- by chemically signalling to parts of the plant.
It responds with VOCs (volatile organic compounds), hormones, or become pathogen-resistant. VOCs are emitted via leaves of root systems.
2.) Interspecific signalling (between different plants): in response to clipping and herbivory, emitter of VOCs and hormones sent chemical signals to surrounding plants (called receiver).
Phylogeny
Every species is connected to a common ancestor
What characterises the classification species?
-Most fundamental level of classification
-Set of individuals are closely related by descent from a common ancestor
-Members of species can interbreed with each other and bring fertile offspring
-Cannot interbreed with individuals of other species, HOWEVER partial interbreeding can occur, resulting in a subspecies
Hierarchical Classification
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Phyletic Groups
-Closely related species are grouped into genera
-All species included in the genus are related to each other by a common ancestor: monophyletic group
-If they are not related to a common ancestor: polyphyletic group (similar species from different ancestors)
Cladistics
Plants are categorised into groups based on hypotheses of the most common recent ancestors
2 aspects of Plant Resemblance
- Descent from a common ancestor: similar features, called synamorphies
- Convergent evolution: Two distinct evolutionary lines of plants that respond similarly to environments and the selection pressure. This results in similar phenotypes called homoplasies.
How can we classify plants?
-Morphometry: Simple observation of major parts
-Microscopy: checking hairs, stomata, cuticle
-Internal structure: plastids in the phloem
-Metabolism: pigments, CAM and C4 Metabolism, anti predator compound presences
-DNA sequencing: sequence of nucleotides, (differences in phenotypes are related to differences in genotypes)
–Use Plastid DNA: inherited maternally, stay highly conserved, the protein rbcL is used as a marker.
–Nuclear genes: ribosomal genes are grouped together (easy to find: markers are 18S and 26S ribosomal genes, which have internal transcribed spacers)
Cladograms
Diagrams that show evolutionary patterns:
-each point (node) where the diagram branches, represents the divergences of one taxon into two.
-All of the branches that extend from any particular point, represents the descendants of the original group (the common ancestor)
