Flashcards in lecture 6 Light and plant development Deck (54)
What is light needed for with plants?
Light is needed as a source of energy in the process of photosynthesis. Additionally it is a source of information for plants.
What does light provide plants?
It provides plants critical information about its light environment, which they needs in order to:
Grow to a certain size or shape
Induce protective substances
What are plants senstive and react to?
quality of light
intensity of light
duration of light
the direction of light
How do plants respond to the light stimuli?
by growing, differentiating, tracking time of day and even seasons, and moving toward or away from the light.
What do plants use the evolved highly sensitive mechanisms for perceiving light for?
regulating developmental changes.
What do plants need in order to initiate development from dark to light growth?
Explain etiolated growth
Seedling grown in dark have a pale, unusually tall appearance, known as etiolated growth.
What is the appearance of seedlings grown in light?
vigorous, green appearance
In relation to seedling growth why wan't photosynthesis drive this transformation?
chlorophyll is not present during that time.
What induces the initial rapid changes for de-etiolation?
distinctly different light response called photomorphogenesis.
What are the light-mediated changes in plant growth and development called?
What are the important pigments that can promote the responses in plants called?
What do Photoreceptors absorb?
Red, Far-red and blue light
List the different parts of the flowering plants from top to bottom
Terminal bud containing shoot apex
Root apex, covered with root cap
What is a Phytochrome?
Phytochrome is a protein pigment that absorbs red light (650 – 680 nm) and far-red light (710 – 740 nm); plays a key role in light-regulated vegetative growth and reproductive development.
What do spectrophotomete studies indicate?
that the phytochromes are concentrated in meristematic regions of plants.
What do the different phytochromes regulate?
distinct processes in plants and their response can be classified according to the amount and quality of light required to produce the effect.
Where is phytochrome present in dark-grown or etiolated plants?
in a red-light absorbing form (Pr), is converted by red light to a far-red light-absorbing form (Pfr), whichis physiologically active form of phytochrome.
What can Pfr be converted to?
What is the conversion of Pfr to Pr?
This conversion/ reconversion is a distinctive property of phytochrome and known as photoreversibility.
What does Phytochrome regulate?
Phytochrome regulates the transcription and expression of several genes mainly involved in greening (de-etiolation).
The complete reversal of etiolation symptoms by light involves?
long term alteration in metabolism that can be brought about by changes in gene expression.
Phytochrome also regulates the?
sleep movement of leaves referred to as nyctinasty and is a well described example of plant response regulated by light.
In nyctinasty leaves extend horizontally (open) to?
face the light during day and fold together vertically (close) at night.
Nyctinastic leaf movements are exhibited by?
many legumes such as Mimosa and Albizia.
Phytochrome brings about leaflet closure by?
regulating membrane potentials and ion fluxes.
What is Photoperiodism?
Photoperiodism is the ability of the plant to detect day length, which makes it possible for an event to occur at a particular time of the year, showing a seasonal response.
Plant photoperiodic responses utilize phytochrome as?
a primary photoreceptor, with subsequent specific signal transduction pathways to regulate different responses.
The classification of plants according to their photoperiodic response is usually based on the flowering time: For Short-day plants?
Flower only in a short days