Question: Phtochromes are the what in a plant that are sensitive to light?
About the article "Botany", section "Plant hormones".

Candidate passages:
C-41 film consists of an acetate or polyester film base, onto which multiple emulsions are coated.
Each layer is only sensitive to a certain color of visible light.
In the classic illustrative example, there are three emulsions: one is red sensitive, another is green sensitive, and the last is blue-sensitive.
The top layer is blue-sensitive.
Beneath the blue layer is a yellow filter, composed of dyes or colloidal silver.
All silver-based photographic emulsions have some sensitivity to blue light, regardless of what other colors they may be sensitized for.
This filter layer serves to remove the blue light, which would expose the layers beneath it.
Beneath the blue-sensitive layer and the yellow filter are the green and red sensitive layers.
The illustrative example outlined above differs from the design of actual film, in respect to the number of layers.
Almost all C-41 films contain multiple layers sensitive to each color.
Each of these layers have different speed and contrast characteristics, allowing the film to be correctly exposed over a wider range of lighting conditions.
In addition to multiple emulsion layers, real films have other layers that are not sensitive to light.
Some films are top-coated with UV blocking layers or anti-scratch coatings.
There also may be layers to space different emulsions, or additional filter layers.
Each emulsion layer, in addition to the light-sensitive components, contain chemicals called dye couplers.
These couplers, located in the blue, green and red-sensitive layers, produce yellow, magenta and cyan dyes, respectively, when developed. 
Chamaecrista nictitans (Sensitive Partridge Pea, Small Partridge Pea or Wild Sensitive Plant) is a herbaceous species of legume widely distributed through the temperate and tropical Americas.
It is an annual plant capable of rapid plant movement—its leaflets fold together when touched.
It is similar to "Chamaecrista fasciculata" except that the leaves are smaller. 
Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium.
Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term as light-induced damage to PSII.
In living organisms, photoinhibited PSII centres are continuously repaired via degradation and synthesis of the D1 protein of the photosynthetic reaction center of PSII.
Photoinhibition is also used in a wider sense, as dynamic photoinhibition, to describe all reactions that decrease the efficiency of photosynthesis when plants are exposed to light. 
Photomultiplier tubes are vacuum phototubes that amplify light by accelerating the photoelectrons to knock more electrons free from a series of electrodes.
They are among the most sensitive light detectors but are not well suited to photography. 
Visible-light astronomy encompasses a wide variety of observations via telescopes that are sensitive in the range of visible light (optical telescopes).
It includes "imaging", where a picture of some sort is made of the object; "photometry", where the amount of light coming from an object is measured, "spectroscopy", where the distribution of that light with respect to its wavelength is measured, and "polarimetry" where the polarisation state of that light is measured.
An example of spectroscopy is the study of spectral lines to understand of what kind of matter light is going through.
Visible astronomy also includes looking up at night ().
Visible-light astronomy is part of optical astronomy.