week 25 Flashcards
what is a circadian rhythm
an internal biological clock which regulates our biological processes. allow things to happen at particular times.
what do the phytochrome, cryptochrome and phytotropin regulatory photoreceptors detect
phytochromes= detect mainly red and far-red light
Cryptochromes and phytotropins= both detect UV-A and blue light
what is the UV-B photoreceptor UVR8
responds to UV-B radiation from sunlight.
what is the structure of a photoreceptor
The apoprotein is the photoreceptor protein.
the chromophore is a small light-absorbing molecule attached to apoprotein.
chromophore+apoprotein comprise the photoreceptor.
what is the phytochrome regulatory photoreceptor structure
phytochrome apoprotein binds to linear tetrapyrrole chromosome.
phytochrome exists in 2 forms Pr and Pfr. Pr- dark grown plants, illumination with red makes Pfr. Pfr illuminated by far-red makes Pr.
what are CAB genes in plants
code for chlorophyll a and b- binding proteins
what is CAB gene transcription in plants
The process of CAB (chlorophyll a and b- binding) genes are transcribed into mRNA so the plant can produce light-harvesting proteins for photosynthesis.
how is vegetation shade detected in plants
The shade avoidance response is controlled by phytochrome. Plants use this mechanism to detect their neighbours by increase in far-red reflection, indicating the proximity of neighbours.
How does the regulatory photoreceptor cryptochrome work
Cryptochromes bind flavin and pterin chromophores that absorb UV-A and blue light.
what do cryptochromes control in plants
invloved in controlling processes such as stem extension, gene expression and flowering time.
how do phototrophins (regulatory photoreceptor) in plants function
bind flavin chromophores that absorb mainly UV-A and blue light. they control several plant responses including phototropism.
what is phototrophism
the growth response of a plant in reaction to light direction
why dont plants get sunburn
Flavonoids play a role in protecting the plant by absorbing UV-B
how can we achieve food security
expand- more land surface
intensity- more yield/ higher nutrition
be smart- grow right crop in right place at right time. manage distribution/ resources
what are the main causes of hunger
war, natural disaster, poverty, access
what are the major food crops
soybean, sweet potato, rice, potato, tomato, cassava, maize, wheat and barley.
why is wheat popular
high nutritional value, long shelf life, and contains gluten
how is rice cultivated (two methods)
traditional wet (paddy fields)- work-intensive, natural weed control, natural fertilisation.
dryland cultivation- easy sowing + harvest, needs herbicides + fertilisers
how does good land become marginal
over-use, salinisation, pollution, climate change
how does intensive agriculture lead to secondary salinity
irrigation water contains salt, considerable amount of irrigation water evaporates leaving salt behind.
how can salt-tolerant crops be generated
Vacuoles in plant cells store toxic substances. NHX1 transports toxic Na+ into vacuole in exchange for protons. NHX1 overexpression improves plant growth in salt.
what does the stress hormone ABA do in plants
close the stomata when plants are experiencing water deficit. ABA is abscisic acid. ABA induces protective response when perceived by ABA receptors, closing stomata on leaves and reducing water loss.
what are the downsides of the ABA hormone effects in plants
although reduced water loss is positive, reduced CO2 uptake and overheating are negative effects
