Original video: https://youtu.be/H9wIKyYp3Is
Delivered on: 08 DECEMBER 2022
This video explores the fascinating ways in which sunlight influences plant growth, development, and behavior. 🌿 We'll go beyond photosynthesis to uncover the diverse roles of sunlight as a signal that regulates various plant processes.
Sunlight serves not only as an energy source for photosynthesis but also as a signal that regulates various developmental processes, from seed germination to fruit development and senescence (Figure 16.1). Sunlight also provides directional cues for plant growth as well as nondirectional cues for plant movements.
We have already touched on several light-sensing mechanisms in the preceding chapters. In Chapter 9 we saw that chloroplasts move within leaf palisade cells to orient either their face or edge toward the sun (see Figure 9.12). The leaves of many species are able to bend toward the sun during its progress across the sky, a phenomenon known as solar tracking (see Figure 9.5). As discussed in Chapter 10, stomata use blue light as a signal for opening, a sensory response that enables CO2 to enter the leaf.
In later chapters we will encounter examples of light-regulated plant development. For example, many seeds require light to germinate, a process called photoblasty. Sunlight inhibits stem growth and stimulates leaf expansion in growing seedlings, two of several light-induced phenotypic changes collectively referred to as photomorphogenesis (Figure 16.2; also see Chapter 18). Most of us are familiar with the observation that the branches of house- plants placed near a window grow toward the incoming light. This phenomenon, called phototropism, is an example of how plants alter their growth patterns in response to the direction of incident radiation (Figure 16.3; also see Chapter 18).
In some species the leaves fold up at night (nyctinasty) and open at dawn (photonasty). Photonastic movements are plant movements in response to non-directional light. As we will discuss in Chapter 20, many plants flower at specific times of the year in response to changing day length, a phenomenon called photoperiodism.
In addition to visible light (Figure 16.4), sunlight also contains ultraviolet (UV) radiation, which can damage membranes, DNA, and proteins (see Chapter 24). Many plants can sense the presence of UV radiation and protect themselves against cellular damage by synthesizing simple phenolics and flavonoids that act as sunscreens and remove damaging oxidants and free radicals that are induced by the high-energy UV photons.
Complementary Slides- Genome Structure and Gene Expression
Keywords: Plant physiology, sunlight, light signaling, photosynthesis, photoreceptors, chloroplast movement, solar tracking, stomata, photoblasty, photomorphogenesis, phototropism, nyctinasty, photonasty, photoperiodism, ultraviolet radiation
Location:
Faculty of Agriculture, Universiti Putra Malaysia
Fakulti Pertanian, Universiti Putra Malaysia, 43000 Seri Kembangan, Selangor
XPMM+9J Seri Kembangan, Selangor
2.9845517506267742, 101.73803356324866
Attribution 4.0 International — CC BY 4.0 - Creative Commons
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