Photoreceptor organelles

Photomotile Responses Photoreceptor Organelles Light-Tracking Strategies 122-2... 

Matsuoka, T., Tokumori, D., Kotsuki, H., Ishida, M., Matsushita, M., Kimura, S., Itoh, T., and Checcucci, G., Analyses of structure of photoreceptor organelle and blepharismin-assodated protein in unicellular eukaryote Blepharisma, Photochem. Photobiol, 72, 709, 2000. 

For directional responses, the photoreceptor molecules (or an array of those) are necessarily — at least for the duration of the photoreaction — located in a matrix with a fixed orientation to the bending organelle, or to the whole body of freely swimming organisms. 

One further problem is the large overshoot in ABA production in wilted leaves. With applied ABA a doubling of the ABA content of the leaf is usually adequate for stomatal closure, while increases up to 40-fold have been reported in wilted leaves. However, extractions of whole leaves do not take into account the location of ABA within the leaf. Perhaps much of the hormone is sequestered in a compartment that has no access to the guard cells. Thus, it would be of much importance to determine the distribution of ABA at the tissue level as well as its intracellular location. Since ABA is a small water-soluble molecule, conventional fractionation techniques may not be suitable to determine its distribution in various organelles. A highly specific immunological method for detection of ABA has recently been developed (38, 39). It is conceivable that this technique could be further developed for determining the cellular localization of ABA as has already been done for the photoreceptor phytochrome (77, 78). 

Photoreceptors light-trapping organelles (q.v.) or molecules in organisms. 

The short one, which appears motionless during swimming (3), is simple and presents close to its base an organelle that could act as a photoreceptor. Near to this organelle and within the chloroplast is the stigma (4). 

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