how does light intensity affect the rate of photosynthesis?

Note that standard output (not HO, not overdriven) T5 tubes are even more efficient but the low light intensity compared to T5HO tubes means they aren't usually used for plant lights.

The Envirolite type CFL has just awful performance.

In practice, any one of these factors could limit the rate of photosynthesis.

The relationshipbetween light intensity and photosynthesis is curvilinear; thus, a leafdoes not have to be in full sunlight to photosynthesize at a maximal rate.

how does temperature affect the rate of photosynthesis?

Farmers can use their knowledge of these limiting factors to increase crop growth in greenhouses. They may use artificial light so that photosynthesis can continue beyond daylight hours, or in a higher-than-normal light intensity. The use of paraffin lamps inside a greenhouse increases the rate of photosynthesis because the burning paraffin produces carbon dioxide, and heat too.

Effects of Blue and Red Light on the Rate of Photosynthesis

It would be most efficient for a treeto have some mechanism for allowing some sunlight to get past its outermostleaves and stimulate photosynthesis in its interior leaves.

Photometry and Photosynthesis | All Things Lighting

where E is the energy in joules, h is Planck’s constant (6.626 x 10-34 joule-seconds), c is the speed of light (2.998 x 108 meters per second), and l is measured in meters. For example, one micromole of photons with a wavelength of 450 nm has 0.266 joules of energy. Scaling the photon-weighted relative quantum yield values by the wavelength and normalizing produces the energy-weighted relative quantum yield, also known as the action spectrum (FIG. 3). (An action spectrum is simply a plot of biological effectiveness as a function of wavelength of incident light.)


The energy-weighted photosynthetic photon flux is measured in watts (joules per second), and is referred to as the yield photon flux (YPF). (In terms of lighting design, it is synonymous with irradiance.) As shown by McCree (1972b), photon-weighted PPFD is a better predictor of photosynthesis when light sources with different spectral power distributions are considered. Given this, PPFD is the metric most commonly used by horticulturalists. However, energy-weighted YPFD is useful for energy-balance calculations involving photosynthetic organisms.


As noted by McCree (1972a), neither PPFD (quantum flux density) nor YPFD (irradiance) are perfect measures of photosynthetically active radiation in that both systematically overestimate the effectiveness of blue light relative to red. As can be seen from FIG. 3, the error is greater for YPFD, which explains why PPFD measurements are preferred by horticulturalists. Nevertheless, they are useful in that they are independent of any particular plant species, and they can be measured both in the laboratory and in the field using a radiometer with a spectrally-calibrated quantum sensor such as the LI-190SA with LI-COR ().

Why does white light affect the rate of photosynthesis more?

When sugar levels are low, the plant takes nutrients and sugars from older leaves to maintainnew leaves. To help plants in an indoor environment, two options are available: (1) raise lightlevels to increase photosynthesis and sugar production or (2) reduce night temperature to lowerrespiration rates and allow more sugars for growth.