Eco-physiological basis of shade adaptation of Camellia nitidissima, a rare and endangered forest understory plant of Southeast Asia

Abstract

BackgroundCamellia nitidissima, a rare and endangered shrub is narrowly distributed in South China and North Vietnam occurring in forest understory. Their light tolerance mechanism is unclear. We measured photosynthesis and related parameters on 2-years-old cuttings growing at 10, 30, 50 and 100% sunlight. Our research question was: At what light level are C. nitidissima cuttings responding most favorably, and what is the eco-physiological basis for their response to light? We hypothesized that as a forest understory growth of C. nitidissima would respond most favorably at low to intermediate light by optimizing photosynthetic activity, and high light will affect photosynthetic functions due to photoinhibition, damage of photosynthetic apparatus and concomitant enzyme activity.ResultsWith increasing light, the maximum net photosynthetic rate (PNmax) and apparent quantum yield (AQY) decreased, while the light compensation point increased, and light saturation point first increased followed by a decrease. The PNmax and AQY under 50 and 100% sunlight were significantly lower than that under 10 and 30% sunlight. The chlorophyll fluorescence parameters Fm, Fv, Fv/Fm all decreased under high light (> 50%). The contents of chlorophyll a (Chla), chlorophyll b (Chlb), and carotenoid (Car) decreased with increasing light. Relative conductivity, malondialdehyde (MDA) and proline contents in leaves were significantly increased in high light but we found no significant difference in these indices at 10 and 30% sunlight.ConclusionsWe conclude that C. nitidissima is a shade adapted plant with poor adaptability to high light (> 50%). The novelty of this research is the demonstration of the eco-physiological basis of its light tolerance (conversely, shade adaptation) mechanisms indicated by decreased photosynthetic activity, chlorophyll fluorescence, Chla, Chlb and Car contents and concomitant increase in relative conductivity, MDA and proline contents at high light causing photoinhibition. For artificial propagation of C. nitidissima we recommend growing cuttings below 30% sunlight. For in situ conservation of this valuable, rare and endangered shrub it is necessary to protect its natural habitats.

Parental Shading Regulates Subsequent Seed Germination

“…It is known that close planting leads plants to perceive the shade signal, characterized with the decrease of blue light intensity and the red (R): far-red (FR) ratio, caused by neighboring plants (Keuskamp et al, 2011 , 2012 ; de Wit et al, 2012 ; Jiang et al, 2019 ; Zhang et al, 2019 ; Yang et al, 2020 ). In close planting conditions, competition for light triggers the plant shade response, including the change of flowering time, promotion of stem and petiole elongation, regulation of seed maturation, variation in photosynthetic response, and decrease of crop productivity (Kurepin et al, 2006 ; Jha et al, 2010 ; Elwell et al, 2011 ; Baker et al, 2018 ; Chai et al, 2018 ; Pantazopoulou et al, 2021 ). Thus, plant shade response plays a key role during the plant life cycle, and is especially important for modern agricultural production.…”

Photosynthetic performance and growth responses of Liriope muscari (Decne.) L.H. Bailey (Asparagaceae) planted within poplar forests having different canopy densities

“…Compared with trees, herbaceous plants are more sensitive to environmental changes. Chai found that Camellia nitidissima is a shade-adapted plant with poor adaptability to high light environments [10]. Under-forest illumination conditions are key factors that limit the growth of herbaceous plants in small-scale environments [11].…”

Photosynthetic performance and growth responses of Liriope muscari (Decne.) L.H. Bailey (Asparagaceae) planted within poplar forests having different canopy densities

“…Compared with trees, herbaceous plants are more sensitive to environmental changes. Chai found that Camellia nitidissima is a shade-adapted plant with poor adaptability to high light environments (Chai et al, 2018). Under-forest illumination conditions are key factors that limit the growth of herbaceous plants in small-scale environments (Bartemucci et al, 2006).…”