Light Intensity Influence on Growth and Photosynthetic Characteristics of Horsfieldia hainanensis

Abstract

Due to both anthropogenic and natural causes, the number of Horsfieldia hainanensis has been decreasing each year in the Tongza Branch nursery (109.534 525°E, 18.763 516°N) of the Hainan Academy of Forestry, China. Consequently, the protection of H. hainanensis is urgent, as is that of most rare tree species. To develop a more comprehensive understanding of the H. hainanensis growth environment, we took 3-year-old H. hainanensis saplings as the research object. We controlled the light intensity by setting different shade amounts to explore the growth and photosynthetic characteristics of H. hainanensis under different light intensities. We found that shade can promote growth and increase the contents of certain substances. Light transmittance of 44.41% can increase plant height (by 29.545%) and biomass (by 66.676%). Light transmittance of 16.19% can increase the pigment content; Chl increased by 40.864%, Chl a increased by 38.031%, and Chl b increased by 48.412%. Light transmittance of 7.30% can increase the soil plant analysis development (SPAD) value of each part of the leaf; the leaf base increased by 41.000%, the leaf margin increased by 32.574%, the blade tip increased by 49.003%, and the leaf average increased by 40.466%. The specific leaf area can reduce the specific leaf weight. We also found that compared to full light, reducing the light transmittance can increase the total chlorophyll (Chl), chlorophyll A (Chl a), and chlorophyll B (Chl b) contents, and the Chl-SPAD-leaf base, leaf edge, leaf tip, average content, and light-saturated net photosynthetic rate. This can in turn reduce the apparent quantum efficiency (AQY), light compensation point (LCP), and dark respiration rate (Rd). In addition, we found a strong correlation between seven of the photosynthetic pigment indicators (Chl, Chla, Chl b, Chl-SPAD-leaf base, leaf margin, leaf tip, and mean) and the three photosynthesis physiological parameters (AQY, LCP, and Rd). The light transmittance of 44.41% (one layer of shading net) treatment group was conducive to the growth of H. hainanensis and photosynthetic characteristic improvement. Therefore, our light transmittance selection of approximately 44.4% is significant for the natural return of H. hainanensis.

Effect of Light Intensity on Morphology, Photosynthesis and Carbon Metabolism of Alfalfa (Medicago sativa) Seedlings

“…Transpiration acts as a driving force behind the absorption and transportation of water and inorganic irons to the above-ground part of the plant [43]. Additionally, loss of water through the stomata is an important heat dissipation mechanism [37]. We found that under optimum light conditions (L400 and L500), the P n , T r and g s of alfalfa can be increased and the C i reduced, which in turn enhanced photosynthesis in alfalfa plants.…”

“…The chlorophyll content of leaves of maize (Zea mays) plants grown in low light intensity was significantly higher than that of leaves grown in high light [36], which agrees with our results. Increased Chl b content could be a typical response to low-light conditions that allows shade-intolerant plants to capture more photosynthetically efficient blue light, thereby stimulating adaptive photomorphogenesis and alleviating the negative impacts of shade stress on photosynthetic activities [37]. Yi et al (2020) [38] also found that adequate CO 2 assimilation and fixation promoted sugar accumulation and decreased pigment-protein complexes in leaves in high light intensity, resulting in senescence and chlorophyll degradation.…”

Promoting smart agroforestry of sengon-based arrowroot and cardamom to support food security

“…Light intensity is an important factor for plant growth. Growth and yield productivity including fresh weight and dry weight of plants are significantly affected by an increase in light intensity [32]. This condition is supported by plant photosynthesis which takes place optimally under sufficient light conditions at opened area of monoculture plot.…”

Biodynamic Lighting: Establishing Foundational Considerations for ‘Life-Centric’ Lighting

“…The behaviour of all life forms is defined as coordinated responses such as actions or inactions to an internal or external stimulus Changes in light intensity leads to considerable changes in the spatial orientation patterns. For example, exposure to high intensity tends to reverse the natural lunar-guided foraging patterns, which decrease during brighter moonlight in naturally lit conditions and increase when exposed to high intensity ALAN (5); similarly, slight increase or decrease in light intensity leads to considerable changes in leaf morphology (78), and compared to high intensity light, reduced light intensity can increase the net nutrition rate of plants (79). Spatial heterogeneity in light intensity is also recommended to support the life-sustaining behaviours of certain life forms (67,80).…”