Week 9 Flashcards
What cements adjacent plant cells together?
Middle Lamella
What does the cell wall/middle lamella do?
It prevents cell migration, even in embryos
What does plant developement depend on?
Patterns of cell division and cell enlargement
What connects adajcent cells?
Plasmodesmata which allows selective large molecules to go through
What are the 3 basic types of plant organs?
Stem, leaves (flowers) and roots
What are the three major tissue systems?
Dermal tissue
Ground tissue
Vascular tissue
What are the dermal tissues in plant leaves?
Upper epidermis and lower epidermis
What are the ground tissues in plant leaves?
Palisade parenchyma, bundle sheath parenchyma and spongy mesophyll
What are the vascular tissues in plant leaves?
Xylem and Phloem
What are the dermal tissues in stems?
Epidermis
What are the ground tissues in stems?
Cortex and Pith
What are the vascular tissues in stems?
Xylem and Phloem
With a vascular cambium forming a ring half way through
When did plants and animals split off from each other?
1.6 BYA
What are the similar traits of plant and animal cells?
Mitosis, meiosis, aerobic respiration etc
What was the plant progenitor like?
Autotrophic, cell wall and sessile organism
What was the animal progenitor like?
Heterotropic, lacked cell wall and can move
What is the life cycle of Arabidopsis thaliana?
Germination
Vegetative growth
Floral transition
Flowering
Maturing siliques (embryogenesis)
What are the key features of animal embryogenesis?
Morphogenic changes confinded to a breif embryonic phase
Embryogenesis generates rudimentary miniature scale modules of the adult
Lineage and mobility important in determining and maintaing cell fate (cell intrinsic information)
What are the key features of plant embryogenesis?
Embryogenesis establishes root and shoot polarity (primary meristems)
Establishes radial tissue patterning found in stems and roots
Embryo is determinate whereas subsequent development is indeterminate
Cell fate is determined by position rather than cell type (cell extrinic information)
What is the function of meristems?
Plant (stem cells) they form new cells of a plant, necessary for primary growth
Where are apical meristems found?
They are found at the tips of roots and shoots
What are different about plant stem cells in the meristem?
They retain the ability to divide and produce new cells in a indeterminate manner
What do shoot apical meristems give rise to?
Stem, leaves, flowers, fruit and seeds
What do root apical meristems give rise to?
Primary and lateral roots
What are similarities between plant and animal embryogenesis?
Developement from zygote requires control of cell proliferation and cell fate
Asymmetric cell divisions in the zygote generates cells that undergo distinct devlopmental patterns
Cell fate is controlled by transcription factors that then regulate the expression of specific genes
What are the 2 type of cells that first divide in plant embryos?
Apical and basal cells
What is the protoderm?
Thin outer layer of meristem cells in plant embryos and the growing points of roots and stems
What is the cotyledon?
Leaf cells inside the embryo
What are periclincal cell divisions?
New cell walls form parallel to the tissue surface
What are anticlinal cell divisions?
New cell walls at 90 degrees to the tissue surface
What does the apical cell form?
Apical cell is always on top and will form an embryo
What does the basal cell form?
It is always on the bottom and will always form the suspensor (umbilical cord for plants)
What is the structure of the 8-cell plant embryo?
2 cell Apical embryo region
2 cell Central embryo region
1 cell Hypophysis
1 cell suspensor
What structure of a seedling?
Cotyledons
Shoot apical meristem
Hypocotyl
Primary root which has quiescent center root cap
Who defined the term morphogen?
Alan Turing
What is morphogen?
“form-generating substance”
What is the french flag model?
Different cell fates therefore gene expression are determined by the concentrations of different morphogens
What does position-dependant signalling need?
1- A cue that signifies positions within the developing structure (morphogen)
2- Individual cells must be able to ‘read’ this positional cue
3- Cells must have the capacity to respond to this manner
What is an example of plant morphogens?
Auxin
What does the mutant gurke mean for a plant?
Severly impacts apical formation
What does the mutant fackel?
The central region is gone
What does the mutant monopteros?
The basal region is gone
What does the mutant gnom?
The terminal region has gone
What is monopteros?
A transciption facotor that respondes to auxin (auxin response factor (ARF))
What are lateral meristems?
They are vascular combium and cork cambium which are necessary for secondary growth
What are axillary meristems?
They are formed at the node between the stem and the leaves
What are the 3 functions of the 3 layers in a shoot apex?
Layer 1 - generates epidermis
Layer 2 and 3 - Generate internal tissues
What is the structure of the upper part of the shoot apex?
Shoot apical meristem which is flanked by the leaf primordium
What does the peripheral zone develop into?
The leaf primordia
What does the rib zone develop into?
Structural cells of the stem
How many stem cells does the central zone of the shoot apical meristem in A.thaliana have?
50 stem cells
What does cytohistological staining show?
That the SAM is comprised of distinct cellular layers and functional zones
What happens some stem cells out of the central zone?
They get pushed out into the peropheral zone and rapidally divide to form new organs
This also happens with the central zone with stem tissues
What are the 3 layers and their function in Arabidopsis SAM?
Layer 1 - anticlinal cell divisions - epidermal
Layer 2 - anticlinal cell divisions
Layer 3 - anticlinal and periclinal
What does WUSCHEL do?
Promotes cell division in SAM (mutants do not produce SAM)
What is WUSHEL?
A homeoox transcription factor, induces transcription of genes necessary for SAM function
What are clavata3 mutants like?
Clavata3 mutants make meristem bigger and WUSCHEL expression pattern changed
What is the function of clavata3?
Inhibit meristem growth and controls wuschel expression