Artificial light to control plant growth and photomorphogenesis in greenhouse crops: opportunities and constraints of LEDs

Roberta Paradiso [Dipartimento di Agraria, Università di Napoli Federico II];
Simona Proietti [Istituto di Biologia Agroambientale e Forestale (IBAF), Consiglio Nazionale delle Ricerche (CNR), Porano (Terni)]

Light quantity (intensity and photoperiod) and quality (spectral composition) strongly affect plant growth and morphogenesis.
Many responses of plants to light spectrum are regulated via photoreceptors-complexes of proteins and pigments, which act as antennae to absorb particular wavelengths and to generate signals, involved in the control of plant development and metabolism, by altering the expression of a large number of genes. Specifically, photomorphogenesis includes multiple light-induced responses in plant growth, flowering and adaptation to the environment, and chemical composition of plant tissues. Most responses are unrelated to photosynthesis and are mediated by specialized systems of photoreceptors. Five classes of plant photomorphogenesis related photoreceptors have been characterized in their biochemical features and physiological roles: the phytochromes family, the cryptochromes, the phototropins, the ZTL/FKF1/LKP2 system, and the UVR8.
Current knowledge about plant photomorphogenesis could be applied to horticulture to improve production schedules and crop yield and quality. In this respect, recently light-emitting diodes (LEDs) have been attending special interest from researchers and growers, because of several attractive features, such as the possibility to tailor the light spectrum and to dim the light intensity. Specifically, thank to the narrow-band spectra, LED-technology makes possible to manipulate light quality and intensity to achieve the desired plant response, depending on the specific requirements of the different plant species and development stages.
This article is a brief overview of the effects of modifications of light spectrum on plant photomorphogenesis, and on current research on LEDs in greenhouse horticulture

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