Plants Flashcards
meristematic tissues
root, shoot, stem… they are undifferentiated cells. division of new cells for growth or repair. produce differentiated cells.
adult tissues
specialized cells, present everywhere else. Ground tissues, dermal tissues and vascular tissues
primary growth
Some plants (e.g. grasses) only have primary growth due to activity and differentiation of apical meristems)
secondary growth
only woody plants (not herbaceous) have this. Other plants (the ones you see bark and/or wood), also has a secondary growth, due to activity and differentiation of lateral meristems.`
ground tissues
in the middle of the leaf, the root. carries out metabolic processes and provides physical support. bulk tissue, storage, processing
dermal tissues
protective tissues. present in the outside of the plant. sometimes nutrient absorption
vascular tissues
transport water, minerals and sugar sap around the plant and physical support
apical meristems
the meristems in the buds and roots. adds height or length to shoot system or adds branches to shoot system
roots are different from stems because
there is presence of epidermis with root hairs, large cortex for storage, vascular cylinder (not bundles) and endodermis and pericycle
endodermis
relates to absorption of waterq
pericycle
related to root ramification. adds branches to root system
branch roots
formed by cell divisions of pericycle cells
why secondary growth
when a plant lives for several years and needs to increase physical support and ability to carry water and sap
lateral meristems
located in the stem (undifferentiated cells)
vascular cambium
adds more vascular tissue which provides more support and thickens plant. adds conductive tissues and thickens the shoot or root
cork cambium
allows plant to replace protective tissues with bark as it grows. adds waterproof bark
woody stem is mostly made from
xylem
bark is made from
periderm and phloem and a but of vascular cambium
different from primary structure from a diagram
the xylem and phloem are in rings, not bundles and the periderm replaces the epidermis
ADV AND DISAV of being woody
can grow taller, last longer but it takes more energy, more defence and more likely to be attacked by things
xylem
found in vascular tissue. made up of fibres for support and parenchyma for storage of water and starch and respond to wounding. and conducting cells: conduct water and minerals. conducts water and dissolved minerals from roots to other parts of plant.
why cut flowers under water
xylem must have a continuous water column to function which is why cutting under water is so good for flowers
absorption of minerals and water
they take in minerals through diffusion and then water follow into the xylem through osmosis
root hairs
increase surface area
xylem going up
Once the xylem sap (water + minerals) enters the root xylem, it creates a positive pressure (root pressure) that pushes the sap column upwards up to 10 meters (that is how high the atmospheric pressure can support it)
cohesion tension model
1) transpiration (water loss) at leaves
2. tension in water column extends from leaves to roots
3. water and minerals are pulled through the xylem vessels
4. more absorption happens in roots
adhesion
the tendency of water molecules to stick to other hydrophilic molecules like cellulose (keeps the water column intact during transport; no slipping back)
cohesion
the tendency of water molecules to stick to each other, so that moving water pulls on surrounding water (hydrogen bonds between water molecules)
xylem transport
passive. relies on adhesion, cohesion and transpiration. also relies on ability of roots to replace any water lost by transpiration. if water loss is too much for osmosis, it can use active transport to get enough water. if that doesn’t work, the plant will go under water stress
transpiration
the evaporation of water from the stomates of the leaves by dry, windy or warm air
leaves
do photosynthesis and control transpiration (guard cells)
guard cells
potation ions transport to guard cells. water enters the cells by osmosis and then the stomata opens which allows more transpiration. when potassium ions leave the cells, the stomata closes which has less transpiration
factors that increase transpiration
dry air (low humidity), wind, high temperatures, high stomata number.
phloem
found in vascular tissue complex tissue that conducts star produced through photosynthesis. composed of fibres, parenchyma, sieve tube members and companion cells. they are alive unlike xylem but more organelles die. they connect their cytoplasms together. they are kept alive by companion cells that have a cytoplasm with sieve tube elements. they pump sugars and ions into and out of the sieve tubes causing osmotic changes. this pushes the contents of sugars around
sieve tube members
conducting cells that form continuous sieve tubes. Sieve tube members only have primary cell walls but, when mature, lose their nucleus and vacuoles (degenerate cell). They connect to each other by cluster of pores. Companion cells (specialized type of parenchyma) will carry out cellular functions of sieve tube elements. they retain cytoplasm but no nucleus or vacuoles in maturity. each has a companion cell to control and maintain the life of both cells.
source and sink in phloem
source is leaf cell, sink is root cell
auxin (IAA
Auxin & gibberellin are released by newly produced cells near the apical meristem and diffuse into the zone of elongation.When the apical bud is removed, the lowered IAA concentration allows the cytokinin to act on lateral buds. The buds will develop and the plant will have more branches, therefore more flowers.
root meristem
adds length to roots
gibberellin
Gibberellin promotes germination. Gibberellin will be produced by newly formed cells as abscisic acid is removed and meristems begin to divide.necessary for growing tip of plant. Auxin & gibberellin are released by newly produced cells near the apical meristem and diffuse into the zone of elongation. Gibberellin will stimulate the production of amylase by the seed. Starch will be broken down into maltose to provide energy for the embryo (future plant). Germination will start.
cytokinin
Leaf senescence is an active process involving degradation and remobilization of chloroplasts and nutrients from old leaves to other parts of the plant.
abscisic acid
used for more cell division (mitosis).While still in the ovary, seeds are packed full of abscisic acid by the parent, which induces dormancy. Seed tissues dehydrate and slow their metabolism.
Abscisic acid must be broken down to germinate a seed.
Supplemental cytokinin delays the process of senescence (aging). Germination occurs when the reduction in abscisic acid allows the secretion of gibberellin. When the plant in under water stress (low soil water potential), the roots start to produce abscisic acid which is sent to the leaves. There, K+ ions leave the guard cell, which cause water to also leave the guard cells by osmosis. When flaccid, guard cells will get closer to each other and the stomata (pore) will close, reducing further water loss by the leaves (transpiration) in times of low water availability.
ethylene
Ethylene is a gaseous plant hormone and is responsible form the process of fruit ripening. Ripening involves changes in colour, softening of mesocarp (internal flesh), and development of aroma and sweetening. It is, therefore, a process to facilitate dispersion of seeds. Animals will be attracted to colourful and scented fruits and will eventually disperse the seeds.
phytohormones
will affect growth in other parts of the plant. may stimulate or inhibit:
1) cell division (cytokinesis) affecting the rate of mitosis
2) cell elongation affecting the rate and direction of growth
3) cell differentiation affecting the rate, timing and nature of cell
specialization
tropism
differential growth due to a stimulus. ex. phototropism (plants grow to light), gravitropism (grows opposite to gravity)
how do plants grow to light
If the light comes regularly from one side of the plant, that side ends up with less auxin. Gibberellin does not promote as much elongation in the absence of auxin.Cells on dark side elongate faster, curving the stem toward light. Once the new growth is toward the light, auxins tend to be equal on all sides of the zone of elongation.
cell death
cells with primary and secondary cell walls will lead to cell death. The cell content is lost and only the thick cell wall remains. Tissues with such type of cells are usually related to support of the plant.
parenchyma
found in ground tissue and is alive. It stores starch and has many spaces
sclerenchyma
found in ground tissue, is dead. provides plant support and protection of embryo
collenchyma
found in ground, is alive only cell walls with thick corners, provides flexible support in young stems
epidermis
found in dermal tissue, alive. large SA
periderm
outer layer of stem with secondary growth. it is dermal and can be dead or alive.
angiosperm
flowering plant
gymnosperm
non-flowering plant
angiosperm monocots and dicots
monocot has one cotyledon while dicot has two (primary leaves).
