Excess light absorption can cause a variety of physiological problems for plants, including overheating, dehydration, loss of turgor, photoinhibition, photo-oxidation, and photorespiration, so paraheliotropism can be viewed as an advantageous behavior in high light environments.
[4] In this plant, daily leaf movements are influenced by two main factors: an endogenous circadian oscillator and light-induced signals.
[6][7] The cumulative effect of volume-changes in these motor cells manifests itself on the tissue/organ level as a swelling or shrinking of one or both sides of the pulvinus, which results in the reorientation of the adjacent leaf.
[1] An excess of light leads to three main overarching physiological problems: a surplus of photochemical energy leads to the creation of reactive oxygen species, which are extremely damaging to numerous cellular structures; the temperature of the plant's cells becomes so high that proteins denature and/or that enzyme kinetics are negatively impacted; and transpiration increases, resulting in losses of turgor and photochemical efficiency.
In 2003, Bielenberg et al. used two Phaseolus species, a quantum sensor, a light meter, a thermocouple meter, and an inclinometer to quantitatively demonstrate the effectiveness of this approach: leaves that displayed paraheliotropic behavior experienced lower photon flux densities (light intensity), lower temperatures, and higher water-use efficiency.