Plant Development Flashcards
determinate growth
plant organs stop growing after a certain size.
indeterminate growth
plants keep growing throughout their life due to meristems.
what are the 2 main meristems, where they found and what do they do?
- apical meristems -tips of roots, shoots, and in axillary buds, enables primary growth (increases height)
- lateral meristems -vascular and cork cambium, enables secondary growth (increasing girth, wideness)
apical > height like a for apex of mountain
what does vascular cambium do
-adds secondary xylem and phloem to the organ
what does cork cambium do
-replaces the epidermis with periderm as it cracks and sloughs off.
true or false most meristemic cells will remain meristemic
false, most meristemic cells will differentiate into cell types, tissues, and organs, only some remain meristemic
the root is derived from the RAM which is covered by a root cap, what does a root cap do
protects the root apical meristem from damage as the root elongates
what’s does the zone of divison in primary root growth include and produce?
- includes stem cells/initials of the RAM
- produces new root cells, including cells in the root cap (mitosis)
what happens in the zone of elongation in primary root growth
- most of the growing region of the root
- cell elongation pushes the root tip further down into soil
- 3 tissue systems begin to develop
what happens in the zone of differentiation in primary root growth
-aka zone of maturation
-cell differentiate into specific cell types occurs
whats the outmost primary meristem that will give rise to the epidermis?
the protoderm
ground tissue consists mostly of _ cells, found in the _, created via the _
parenchyma cells found in the cortex, created via the ground meristem
endodermis
- innermost layer of cortex
- a cyclinder 1 cell thick that is a selective barrier regulating movement of substances into the vascular stele
the _ gives rise to the vascular cyclinder (stele)
procambium
the _ is the innermost layer of cells right inside the endodermis. lateral roots arise from this.
pericycle
the shoot is derived from the SAM, which is protected by…
the leaves of the apical bud
shoot elongation is due to the lengthening of
the internodes
SAM gives rise to the to the same primary meristems as the root which are
- protoderm
- ground meristem
- procambium
in shoot development
branching arises from
axillary buds (each with their own apical meristem)
auxin prevents axillary buds from growing close to the apical meristem, what is this called
apical dominance
what do leaf primordia arise from, and what develops from the leaf primordia
the flanks of the shoot apical meristem.
leaves develop from the leaf primordia.
ground tissue consists of the tissues:
- parenchyma
- 1-2 layers collenchyma under epidermis
- some sclerenchyma fibres for support
explain the differences between eudicot vs dicot in the root and shoot cross sections.
- in eudicot roots the xylem is in a x shape, thin endodermis, no pith.
- In the monocot roots xylem is in a ring, thick endodermis, and pith is present.
- in eudicot shoots, vascular bundles are in a ring, pith is present (opp of eudicot roots)
- in monocot shoots vascular bundles are scattered and there is no pith.
what part of the leaf tissue does the protoderm give rise to
epidermis and a thick cuticle
what part of the leaf tissue does the ground meristem give rise to
the mesophyll
what are the two parts of the mesophyll? describe them
- palisade mesophyll -elongated parenchyma on the upper part of the leaf
- spongy mesophyll - loosely arranged parenchyma with large air spaces for movement of CO2 AND O2. (Think sponge)
What are the veins of leaves
bundles of vascular tissue
what is bundle sheath in leaves composed of
parenchyma cells
what directions does secondary growth grow
laterally inside and outside
although primary growth continues in the apical bud, only secondary growth occurs along the _
vascular cambium, thickening the stem.
secondary xylem is to the _ of the vascular cambium, secondary phloem is to the _ of the vascular cambium.
secondary xylem-inside
secondary phloem-outside
some of the initials of the vascular cambium give rise to _. which is?
vascular rays -files of parenchyma cells that connect secondary xylem and phloem and transports water between them, aids in wound repair, and stores carbohydrates.
what happens as girth incr. and the secondary phloem can’t keep up?
- epidermis ruptures, falls off
- cork cambium develops from cortex, producing cork cells
- cork will replace the epidermis
in year 2 as girth increases what happens to the outermost cork cells
they fall off (just like da epidermis did).
what happens if the cork cambium is lost during secondary growth what will happen?
another one will form deeper in the cortex tissue to make more cork cells. if the cortex falls off, the cork cambium will arise from the secondary phloem tissue.
(slide 20 for visual)
each cork cambium and tissues it produces (cork) forms a layer of _
periderm
bark is composed of all the tissues exterior to the _ _
vascular cambium (secondary phloem, remnants of cortex, cork, periderm)
are xylem cells small or large in early wood (in the spring)
large to take in lots of water (xylem- water transport)
are xylem cells small or large in late wood (in the summer)
smaller
what does a thick growth ring mean
warm years, good climate
what does thin growth rings mean?
less flavourable climate.
as secondary xylem becomes older, it loses its transport function and becomes heartwood and sapwood describe these bitches
- heartwood-innermost secondary xylem darker
- sapwood - outmost (younger) secondary xylem, still does transport of water.
what will happen if you remove a ring of bark from the tree
it will die. bc then it cannot transport photosynthates from the shoot to the root. (u can only take off in parts).
lenticels allow for
gas exchange in the stems that have secondary growth.
what’s developmental plasticity
one genotype can result in many phenotypes
what are the three 3 stages of development
- growth -irreversible change in size
- morphogenesis - gives tissues, organs, and bodies their shape and cell positions.
- differentiation -cells become different from one another
flowering shifts the plant from _ growth to _ growth
from vegatative growth to reproductive growth.
what genes regulate floral formation when on
meristem identity genes.
what is flowering triggered by
- environment (light, temp)
- hormones
what do each of the genes in the ABC model of flower formation code for
- A genes > outer 2 whorls
- B genes > middle 2 whorls
- C genes > inner 2 whorls
what gene (of ABC model) codes for:
* sepals
* petals
* stamens
* carpels
- sepals= A (outer)
- petals = A + B (outer/middle)
- stamens= B + C (inner/middle0
- carpels = C (inner)
