Abstract
The significance of the spectral composition of light for growth and other physiological functions of plants moved to the focus of “plant science” soon after the discovery of photosynthesis, if not earlier. The research in this field recently intensified due to the explosive development of computer-controlled systems for artificial illumination and documenting photosynthetic activity. The progress is also substantiated by recent insights into the molecular mechanisms of photo-regulation of assorted physiological functions in plants mediated by photoreceptors and other pigment systems. The spectral balance of solar radiation can vary significantly, affecting the functioning and development of plants. Its effects are evident on the macroscale (e.g., in individual plants growing under the forest canopy) as well as on the meso- or microscale (e.g., mutual shading of leaf cell layers and chloroplasts). The diversity of the observable effects of light spectrum variation arises through (i) the triggering of different photoreceptors, (ii) the non-uniform efficiency of spectral components in driving photosynthesis, and (iii) a variable depth of penetration of spectral components into the leaf. We depict the effects of these factors using the spectral dependence of chloroplast photorelocation movements interlinked with the changes in light penetration into (light capture by) the leaf and the photosynthetic capacity. In this review, we unfold the history of the research on the photocontrol effects and put it in the broader context of photosynthesis efficiency and photoprotection under stress caused by a high intensity of light.
Highlights
The Milestones of Plant PhotobiologyThe light effects on plants started to draw the attention of scientists at the end of the 18th century after Joseph Priestley’s (1772) [1] discovery of photosynthesis and Jan Ingenhousz’s (1779) [2] finding of its dependence on light (though the idea of probable light contribution to “ennobling principles of vegetables” was formulated half a century earlier by Stephen Hales (1727) [3])
The specialists affirm that even though the book was published more than a century ago, it incorporates a large amount of detailed knowledge regarding chloroplast movement, which is useful till nowadays [23]
Strong absorption of red and blue light in the uppermost layers of a leaf would shade the lower cell layers nearly completely. They would not contribute to photosynthesis if it was not for the green component in the daylight spectrum
Summary
The light effects on plants started to draw the attention of scientists at the end of the 18th century after Joseph Priestley’s (1772) [1] discovery of photosynthesis and Jan Ingenhousz’s (1779) [2] finding of its dependence on light (though the idea of probable light contribution to “ennobling principles of vegetables” was formulated half a century earlier by Stephen Hales (1727) [3]). Gustav Senn is generally considered as “the pioneer of chloroplast movement research” [21] due to his seminal book “The Changes in Shape and Position of Plant Chloroplasts” [22] In his book he summarized data on chloroplast migration in response to external stimuli, first of all to light, taking into account the optical properties of individual cells and determining light paths within the cells (Figure 1). The specialists affirm that even though the book was published more than a century ago, it incorporates a large amount of detailed knowledge regarding chloroplast movement, which is useful till nowadays [23] After finishing his fundamental work, Senn “retreated from the study of chloroplasts and became a researcher of the Greek philosopher, Theophrastus” [21].
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