Plant Evolution Pt. 2 Flashcards
What is diffusion?
Movement of minerals along a concentration gradient
What is mass flow?
Uptake of mineral ions by means of a hydrostatic pressure gradient
What is Fungal Hyphae
Absorb minerals from the soil and exchange with sugars from the plant (mutualism)
Define transpiration
Transpiration is loss of water from the stomata of leaves
Explain how guard cells regulate transpiration
Stomata consist of microscopic pores, each flanked by a pair of guard cells. Guard cells can increase or decrease the size of the pore via changes in their turgor status, hence regulating both CO2 entry into the leaf and transpiration, or the loss of water from the leaf.
State the function of abscisic acid in regulating the stomata
A typical effect of ABA on leaves is to reduce transpirational water loss by closing stomata and parallelly defend against microbes by restricting their entry through stomatal pores.
Explain how abiotic factors (light temperature wind and humidity) affect the rate of transpiration
High temperatures increase evaporation rate of water.
High humidity lowers the rate of water evaporation.
High light intensity usually increases photosynthesis which increases transpiration.
Outline the role of phloem in active translocation of sugars and amino acids from source to sink
Phloem tissue transports sugars and amino acids from sources which include photosynthetic tissue (leaves and stems) and storage organs, to sinks which include the fruits, seeds and roots of the plant.
This transport is known as active translocation and requires energy.
Draw and label the structure of a dicotyledonous animal-pollinated flower
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Define pollination
the placement of pollen on the stigma. The transfer of pollen grains from the anther to the stigma (usually of another plant), often facilitated by animals, wind or water movement
Define fertilization
a process of sexual reproduction, which occurs after pollination and germination. Fusion of the male gamete nuclei (in the pollen grain) with the female gamete (in the ovule) to form a zygote
Define seed dispersal
Fertilized ovules form seeds that move away from the parental plant before germination, reducing competition for resources
Draw and label a diagram of the internal and external structure of a named dicotyledonous seed
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Describe the metabolic events of germination in a typical starchy seed
The absorption of water followed by the formation of gibberellin in the emery cotyledon, This stimulates the production of amylase which catalyzes the breakdown of starch into maltose. This maltose then diffuses to the embryo for energy release and growth
Explain the conditions needed for the germination of a typical seed
Germination is the emergence and growth of an embryonic plant from a seed. Water is needed to metabolically activate the cells, proper temperature for optimal functions of enzymes, and oxygen for aerobic respiration (need ATP in order to grow).
What happens if the conditions for the germination of a typical seed are not favorable?
If conditions are not favorable then the seed may remain dormant. This way the seed can survive adverse conditions and only start to germinate when conditions become favorable.
Explain how flowering is controlled in long-day and short-day plants
Flowering in long-day and short-day plants is controlled by a pigment called phytochrome. This pigment exists in two forms, P(sub)r and P(sub)fr which can be converted into each other.
What is P(sub)fr and P(sub)r?
The Pfr form is the active form of phytochrome, while the Pr form is the inactive form of phytochrome
When does P(sub)fr and P(sub)r, convert into each other?
Sunlight contains more red light, so the Pfr form is predominant during the day, with the gradual reversion to the Pr form occurring at night
When is flowering induced in long day plants?
In long day plants, the active Pr form is a promoter of flowering and so flowering is induced when the night period is less than a critical length and Pfr levels are high
When is flowering induced in short day plants?
In short day plants, the active Pfr form is an inhibitor of flowering and so flowering is induced when the night period is greater than a critical length and Pfr levels are low
How does the structure of xylem vessels aid the transpiration stream?
The outer cell walls contain thickenings which resemble spirals/rings with lignin which makes the vessels strong and able to withstand low pressures.
How does evaporation aid the transpiration stream?
Due to evaporation of water from the leaf, the transpiration pull occurs (more water to be pulled up xylem tube due to low pressure)
How does cohesion/adhesion aid the transpiration stream?
Columns of water do not break due to cohesion and adhesion of water molecules (cohesion of water molecules and adhesion of water molecules to walls of xylem)
