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How do plants unlock the secrets of light and control their growth processes?
Light is not only the energy source for plants to carry out photosynthesis, but also an important environmental factor for their growth and development. Many studies have shown that plants use different light-sensing mechanisms to carry out a process called photomorphogenesis, which is the ability of plants to adjust their growth patterns in response to changes in the light spectrum. This mysterious growth regulation mechanism makes scientists even more curious: How do plants decipher the secrets of light and affect their growth?
History of photomorphogenesis
Theophrastus, an ancient Greek philosopher, was one of the first to explore photomorphogenesis. He noticed the effects of light on plant development, especially the different wood properties of pine trees produced under different light conditions. characteristic. In 1686, John Ray mentioned etiolation in his book On the History of Plants, and Charles Bonnet defined etiolation in 1754. The noun for this process is "etiolement".
Key stages of photomorphogenesis
Seed germination
Light has a profound effect on the germination process of plants. When germinating seeds are first exposed to light, roots usually appear first, followed by shoot growth. This process demonstrates how plants use light signals to adjust root and shoot growth. Different growth responses are regulated by hormones.
Seedling Development
When plants are grown in an environment lacking light, they display a trait called etiolated development. These seedlings only rapidly switch to photomorphogenesis when exposed to light. . During this process, the characteristics of etiolated seedlings are significantly different from those of seedlings that received light:Characteristics of etiolation: prominent apical hook, no leaves, no chlorophyll, rapid stem elongation, limited stem radiating growth.
Light morphological characteristics: opening of apical hook or splitting of embryo, promotion of leaf growth, chlorophyll production, inhibition of stem elongation, and promotion of root elongation.
Photoperiodicity
Some plants rely on photoperiodic signals to decide when to switch from vegetative growth to flowering. This phenomenon is called photoperiodism, and it uses red light receptors (phytochromes) to judge day length. The length of the photoperiod affects the flowering time of the plant, allowing it to adapt to seasonal changes.
Photoreceptors in plants
Plants perceive light through different photoreceptors, especially blue, red and far-red light bands.
Red light and far-red light
Plants use phytochromes to detect red and far-red light, and these cues drive photomorphogenesis. These red light-receiving proteins can adjust the plant's growth behavior in different light environments. Notably, different forms of phytochrome regulate different growth responses, and in the absence of one, others may take over its function.
Blue-ray
Plants contain a variety of blue light photoreceptors, which have different functions and are mainly responsible for regulating the growth response of plants under blue light. The discovery of blue light receptors provides key clues for understanding how plants adjust their growth under different light conditions.
Ultraviolet light
Plants respond particularly well to ultraviolet light, especially ultraviolet B (UV-B), which affects plant germination and growth. UV light receptors such as UVR8 can sense UV-B and regulate plant growth and development through different biochemical pathways. In addition, plants must cope with UV damage, which requires them to have adaptive mechanisms.
Through these complex perception mechanisms, plants are able to find their own living space in the changing light. This not only reflects the sensitivity of plants to the external environment, but also gives us a deeper understanding of the adaptability of life. In such circumstances, what strategies will plants adopt to ensure their survival and reproduction when faced with a changing environment?
