...the roots), and light energy (absorbed by...
...CO2, H2O, and light energy to produce...
...orange/red ranges of light. 4. A plant...
...that color of light is reflected. a....
...reflected. a. Reflected light is not absorbed...
...stages: (1) The light reactions capture the...
...Stage 1 The light reactions: capturing energy...
...4.5 In the light reactions, the energy...
...Sunlight drives the light reactions of photosynthesis...
...A. In the light reactions, the energy...
...photosynthesis: a. First stage—light reactions—the energy of...
...3. During the light reaction, pigments in...
...energy. C. The light reactions + 1....
...(provided by the light reactions) and CO2...
...of photosynthesis: a. Light reactions capture energy...
...NADPH from the light reactions 3. CO2...
...linked stages. ATP Light reactions Calvin cycle...
...4.5 In the light reactions, the energy...
...• Photo = light (photosynthesis; process of...
...process of using light energy to make...
...the color of light they use for...
...to think white light or sunlight is...
...products from the light reactions. Both reactions...
...time in the light. The Calvin cycle...
...4.5 In the light reactions, the energy...
...product of the light reactions. ? Excited...
...4.5 In the light reactions, the energy...
...show that white light can be split...
...Shine a strong light on the chlorophyll....
...you shine a light on the chlorophyll,...
...energy as red light. ??If you do...
...Demonstration of the Light Dependent Reactions of...

...to Earth. A light beam passes the...
...fast does the light beam move relative...
...13. Describe the light clock. 14. Velma...
...speed for a light beam? 3. Velma...
...speed for a light beam? Explain. 15....
...speed does the light from the explosion...
...Assuming also that light is a wave...
...is about 26,000 light-years away. Could a...

...environment with greater light, water, wind stresses...
...adaptations: to enhance light absorption to provide...
...(1) Leaf Anatomy Light Availability Water Availability...
...plants compete for light ability to use...
...ability to use light available impacts photosynthetic...
...to use available light effectively - rosette-leaf...
...Leaf Adaptations to Light Availability 11 ©...
...Leaf Adaptations to Light Availability level of...
...leaf anatomy maximizes light absorption through a...
...classified based on light exposure during development...
...of plant alter light exposure leaves in...
...horizontal to maximize light capture 1. Leaf...
...Leaf Adaptations to Light Availability 13 ©...
...Leaf Adaptations to Light Availability {5C22544A-7EE6-4342-B048-85BDC9FD1C3A}Characteristic Sun...
...Leaf Adaptations to Light Availability anatomical adaptations...
...plant depending on light: - sun leaves...
...blades to reduce light exposure - shade...
...surface area for light absorption 15 ©...
...sieve effect / light channeling - spongy...
...– irregular-shaped – light scattering from air...
...Leaf Adaptations to Light Availability anatomical adaptations...
...Leaf Adaptations to Light Availability 17 ©...
...Leaf Adaptations to Light Availability anatomical adaptations...
...exposed to high light 18 © 2009...
...- involved in light reflection, water retention,...
...Leaf Adaptations to Light Availability outer epidermal...
...(trichomes) – deflect light 1. Leaf Adaptations...
...Leaf Adaptations to Light Availability anatomical adaptations...
...reducing exposure to light and wind -...
...surface to access light for photosynthesis and...
...cells to increase light access and maximize...
...exposed to high light, low water availability...
...covering - reflects light (under high light)...
...light (under high light) reduces water loss...

...sound Photoreceptors – light, e.g., vision Electroreceptors...
...eyelid ? perceive light Polymodal receptors Sensitive...
...to detect visible light A small proportion...
...in water Visible light travels well in...
...Range from single light-sensitive cells to complex,...
...bonds Absorption of light converts bond from...
...example, wavelength of light absorbed Phototransduction Steps...
...Detect direction of light Light-dark contrast Some...
...direction of light Light-dark contrast Some can...
...Some sense of light direction and intensity...
...aperture Discrimination of light direction and intensity...
...direction and intensity Light-dark contrast Image formation...
...intensity Lens refracts light and focuses it...
...wave properties of light Increasing the number...
...animals that reflects light Figure 6.35 The...
...in iris allows light into eye Lens...
...Refraction – bending light rays Both the...
...lenses to focus light on the retina...
...Image Accommodation Incoming light rays must converge...
...point at which light waves converge Focal...
...point Distant objects Light rays are parallel...
...Little refraction of light by lens Close...
...lens Close objects Light rays are not...
...More refraction of light by lens The...
...detect contrasts between light and dark Signal...
...improve contrast of light and dark “Center-surround”...
...cells Stimulated by light in center of...
...field Inhibited by light in periphery of...
...different wavelengths of light Requires multiple types...

...such as temperature, light, water, and nutrients...
...nearly all ecosystems. Light intensity is not...
...intense competition for light in the understory....
...In aquatic environments, light intensity limits the...
...45% of red light and 2% of...
...2% of blue light passing through it....
...surface. Too much light can also limit...
...and chemically stratified. Light is absorbed by...
...photosynthetic organisms, so light intensity decreases rapidly...
...There is sufficient light for photosynthesis in...
...zone. Very little light penetrates to the...
...water, degree of light penetration, distance from...
...and competition for light is intense. There...

...body, including heat, light, pressure, and chemicals....
...sensory receptor absorb light. The resulting flow...
...stimulus possible. Most light receptors can detect...
...quantum (photon) of light; chemical receptors can...
...potential triggered by light striking the eye...
...few photons of light that triggered it....
...stimulus, such as light or cold. Distinct...
...Receptors that detect light touch are close...
...such as visible light, electricity, and magnetism....
...respond to visible light and are often...
...Many types of light detectors have evolved...
...and intensity of light to complex image-forming...
...some kind of light-detecting organ. The ocelli...
...cells that block light. Light shining on...
...that block light. Light shining on a...
...right and forward, light shining from one...
...away from the light source until it...
...with its own light-focusing lens. Each ommatidium...
...Each ommatidium detects light from a tiny...
...50 flashes of light per second, the...
...can see ultraviolet light. Single-lens eyes are...
...the vertebrate eye. Light enters through the...
...more or less light. Behind the pupil,...
...single lens focuses light on a layer...
...cornea, which lets light into the eye...
...the amount of light entering the pupil,...
...a “blind spot”: Light focused onto that...
...role in focusing light onto the retina....
...rods, which are light sensitive but do...
...which are less light sensitive but provide...
...green, or blue light. Rods are most...
...night vision. The light-absorbing pigment rhodopsin triggers...
...pigments consisting of light-absorbing molecules called retinal...
...rods. Absorption of light by rhodopsin shifts...
...of rhodopsin by light is called “bleaching.”...
...cyclic GMP in light closes Na+ ion...
...In very bright light, rhodopsin remains bleached...
...the amount of light falling on the...
...move from bright light to a dark,...
...photopsin to absorb light optimally at a...
...synapse. In the light, rods and cones...
...this physical arrangement, light must pass through...
...reach the photoreceptors. Light intensity is not...
...illuminated, making the light spot appear lighter...
...exactly where the light struck the retina....
...molecules that absorb light. Animals as diverse...
...in response to light. Concept 50.5 The...
...a pattern of light and dark bands....
...Flying animals are light, with body masses...

...the absence of light. For example, a...
...the absence of light. A plant growing...
...signal—in this case, light—and how this reception...
...when exposed to light. Injecting additional phytochrome...
...exposing them to light produced a normal...
...phytochrome functions in light detection during de-etiolation....
...a specific enzyme. Light causes phytochrome to...
...mutants have a light-grown morphology (expanded leaves...
...chlorophyll production requires light. The mutants have...
...normally activated by light. When the negative...
...grown in the light. During post-translational modifications...
...plants grow toward light led to the...
...Plants grow toward light; if you rotate...
...again face the light. Any growth response...
...a shoot toward light is called positive...
...growth away from light is negative phototropism....
...curves toward the light as a result...
...seedling bent toward light only if the...
...responsible for sensing light, the actual growth...
...normally, bending toward light. If the tip...
...coleoptile curved toward light because of a...
...to grow toward light, based on the...
...as exposure to light or low temperatures,...
...to those of light-grown plants even when...
...optimal conditions of light, temperature, and moisture....
...Other seeds require light or prolonged exposure...
...39.3 Responses to light are critical for...
...for plant success. Light is an especially...
...lives of plants. Light is required for...
...The effects of light on plant morphology...
...biologists call photomorphogenesis. Light reception also allows...
...and wavelength of light. A graph called...
...that depends on light. A close correspondence...
...red and blue light are the most...
...major classes of light receptors: blue-light photoreceptors...
...of light receptors: blue-light photoreceptors and phytochromes...
...absorb mostly red light. The action spectra...
...demonstrate that blue light is effective in...
...identity of the blue-light photoreceptor was so...
...that detect blue light. Cryptochromes are molecular...
...in response to light. There is debate...
...is the major blue-light photoreceptor involved in...
...plant responses to light. Phytochromes were discovered...
...near-optimal conditions, especially light conditions. Such seeds...
...many years until light conditions change. For...
...create a favorable light environment. In the...
...action spectrum for light-induced germination of lettuce...
...minutes of monochromatic light of various wavelengths,...
...germinated under each light regimen. Red light...
...light regimen. Red light (660 nm) increased...
...germination, but far-red light (730 nm) inhibited...
...last flash of light; the effects of...
...red and far-red light are reversible. The...
...red and far-red light is a phytochrome....
...a chromophore, the light-absorbing part of the...
...Pr absorbs red light maximally and converts...
...Pfr absorbs far-red light maximally and converts...
...that controls various light-induced events in the...
...developmental responses to light. For example, Pr...
...exposed to red light is converted to...
...exposed to red light (along with other...
...the quality of light. During the day,...
...to changes in light conditions. For example,...
...that requires high light intensity might use...
...out more red light than far-red light....
...light than far-red light. The tree could...
...to changes in light levels, temperature, and...
...kept in constant light or constant darkness....
...may disrupt a light-dependent mechanism that sets...
...the biological clock. Light entrains the biological...
...Both phytochrome and blue-light photoreceptors can entrain...
...in winter. In light-regulated chambers, the Maryland...
...it required a light period shorter than...
...only when the light period is longer...
...minutes of dim light. Short-day plants are...
...few minutes of light. Although the critical...
...of plant. Red light is the most...
...flash of red light during the dark...
...flash of far-red light, the plant detects...
...a flash of light, the floriculture industry...
...stimuli other than light. Because of their...
...and physiological mechanisms. Light is one important...

...cells that allow light to penetrate to...
...high temperatures and light intensity of the...
...shoot systems acquire light and CO2 for...
...evolved, competition for light, water, and nutrients...
...advantage in absorbing light. The increased surface...
...mechanisms for acquiring light from the sun,...
...designed to capture light. Stems support leaves...
...maximum exposure to light and reducing shading...
...Leaf orientation affects light absorption. Some plants...
...low levels of light, horizontal leaves effectively...
...to levels of light that are too...
...the absorption of light for photosynthesis. Leaf...
...marsh plants. High light intensities and low...
...opening at dawn: light, CO2 depletion, and...
...cells. Illumination of blue-light receptors in the...

...photosynthesis to capture light energy from the...
...are photoautotrophs, using light as a source...
...10.1 Photosynthesis converts light energy to the...
...the absorption of light energy during photosynthesis....
...membranes. Powered by light, photosynthesis produces organic...
...+ 12H2O + light energy C6H12O6 +...
...+ 6H2O + light energy C6H12O6 +...
...+ H2O + light energy + O2,...
...is provided by light. A preview of...
...with multiple steps: light reactions and the...
...Calvin cycle. The light reactions (photo) convert...
...energy from the light reactions to incorporate...
...as a by-product. Light absorbed by chlorophyll...
...forming NADPH. The light reaction also generates...
...called photophosphorylation. Thus, light energy is initially...
...of cells. The light reactions produce no...
...ATP from the light reactions also powers...
...NADPH from the light reactions. The metabolic...
...to as the light-independent reactions because none...
...the steps requires light directly. Nevertheless, the...
...is when the light reactions can provide...
...the chloroplast uses light energy to make...
...photosynthesis. Whereas the light reactions occur at...
...Concept 10.2 The light reactions convert solar...
...ATP and NADPH. Light is a form...
...of electromagnetic energy, light travels in rhythmic...
...band of visible light detected as various...
...human eye. Although light travels as a...
...permitting only visible light to pass in...
...significant quantities. Visible light is the radiation...
...Photosynthetic pigments are light receptors. When light...
...light receptors. When light meets matter, the...
...meets matter, the light may be reflected,...
...red and violet-blue light while transmitting and...
...and reflecting green light. A spectrophotometer measures...
...various wavelengths of light. A spectrophotometer beams...
...narrow wavelengths of light through a solution...
...the fraction of light transmitted at each...
...plots a pigment’s light absorption versus wavelength....
...versus wavelength. The light reactions can perform...
...those wavelengths of light that are absorbed....
...directly in the light reactions, absorbs best...
...different wavelengths of light. Areas receiving wavelengths...
...directly in the light reactions, but accessory...
...photosynthetic pigments absorb light and transfer energy...
...photoprotection against excessive light. These compounds absorb...
...and dissipate excessive light energy that would...
...other pigments absorb light, an electron is...
...some pigments emit light after absorbing photons,...
...by absorption of light energy produces very...
...a number of light-harvesting complexes. Each light-harvesting...
...light-harvesting complexes. Each light-harvesting complex consists of...
...photosystem to harvest light over a larger...
...can. Together, the light-harvesting complexes act as...
...step of the light reactions. As soon...
...complex surrounded by light-harvesting complexes—functions in the...
...slight differences in light-absorbing properties. These two...
...together in using light energy to generate...
...NADPH. During the light reactions, there are...
...chloroplasts. During the light reactions, electrons flow...
...a photon of light. One of the...
...in chemiosmosis. Meanwhile, light energy has excited...
...Calvin cycle. The light reactions use the...
...well in low light, but they do...
...grow well where light is intense. This...
...protecting cells from light-induced damage. Chloroplasts and...
...ATP; chloroplasts transform light energy into the...
...To summarize the light reactions: Electron flow...
...potential energy. The light-driven electron current also...
...thylakoid membrane converts light energy to chemical...
...six NADPH. The light reactions regenerate ATP...
...carbohydrates. Neither the light reactions nor the...
...released from the light reactions increases. These...
...rise as the light reactions convert light...
...light reactions convert light to chemical energy....
...induced by excess light. This is clear...
...products of the light reactions, which build...
...the day, the light reactions supply ATP...
...of photosynthesis. The light reactions capture solar...