Sunflower Leaf Structure Affects Chlorophyll a Fluorescence Induction Kinetics In Vivo

Abstract

Chlorophyll a fluorescence induction kinetics (CFI) is an important tool that reflects the photosynthetic function of leaves, but it remains unclear whether it is affected by leaf structure. Therefore, in this study, the leaf structure and CFI curves of sunflower and sorghum seedlings were analyzed. Results revealed that there was a significant difference between the structures of palisade and spongy tissues in sunflower leaves. Their CFI curves, measured on both the adaxial and abaxial sides, also differed significantly. However, the differences in the leaf structures and CFI curves between both sides of sorghum leaves were not significant. Further analysis revealed that the differences in the CFI curves between the adaxial and abaxial sides of sunflower leaves almost disappeared due to reduced incident light scattering and refraction in the leaf tissues; more importantly, changes in the CFI curves of the abaxial side were greater than the adaxial side. Compared to leaves grown under full sunlight, weak light led to decreased differences in the CFI curves between the adaxial and abaxial sides of sunflower leaves; of these, changes in the CFI curves and palisade tissue structure on the adaxial side were more obvious than on the abaxial side. Therefore, it appears that large differences in sunflower leaf structures may affect the shape of CFI curves. These findings lay a foundation for enhancing our understanding of CFI from a new perspective.

Vertical variation in leaf functional traits of Parashorea chinensis with different canopy layers

“…The trade-off between low LCP, respiration rates and high maximum photosynthetic rates of the leaves of P. chinensis in habitat shift from low canopy to high canopy reflected its change in ecological adaptation, which are similar to the pattern of the strategy of different sizes of trees from understory to canopy ( Deng et al., 2020 ). The leaf morphological and structural trait is also likely to express the responses to the resource gradients ( Wright et al., 2004 ; Reich, 2014 ), P. chinensis increased the thickness of the palisade tissue to enhance CO 2 diffusion pathways and dissolution area ( Zou et al., 2022 ), promoting leaf light capture ability and the concentration of photosynthesis-related enzymes ( Jiao et al., 2022 ), leading to LT increased and LD declined ( Poorter et al., 2009 ). In general, plants will invest more nitrogen for photosynthesis on strong light conditions to increase photosynthetic efficiency.…”

Hyperspectral and Chlorophyll Fluorescence Analyses of Comparative Leaf Surfaces Reveal Cellular Influences on Leaf Optical Properties in Tradescantia Plants

“…Chlorophyll fluorescence primarily indicates the photosynthetic efficiency of leaf surface cells, thereby emphasising the functional implications of morphological variation [ 2 , 28 , 30 , 66 , 67 ]. By measuring the fluorescence emitted by a flash or detection between two sensors that penetrated the mesophyll tissue profile, we ascertained that the internal leaf signals diminished upon the sensor return [ 1 , 11 , 14 , 68 ]. For example, this determines how light dispersion varies among different cellular layers and the impact of adaxial and abaxial hypodermal cells, which contain purple pigments, on the epidermis.…”

“…The differences in fluorescence induction kinetics and JIP test parameters across leaf surfaces highlight the influence of cellular and subcellular frameworks on the quantum yield of electron transport and potentially indicating stress or a higher capacity for non-photochemical quenching [ 2 , 68 , 84 , 85 ]. Such insights are vital for elucidating how structural attributes steer physiological processes, including photosynthesis and stress responses.…”

“…Chloroplasts, as organelles housing essential pigments such as chlorophylls and carotenoids, are integral to light absorption for photosynthesis, whereas vacuoles contain anthocyanins and flavonoids for directional light scattering and photoprotection [ 17 , 34 , 68 , 91 ]. Varied chlorophyll a / b ratios and carotenoid quantities across species indicate differing approaches to light energy utilisation, possibly as an adaptive response to their distinct lighting environments [ 2 , 92 , 93 ].…”

“…Furthermore, the elevated anthocyanin and flavonoid levels in Tradescantia spathacea suggest a robust ability to mitigate UV damage and oxidative stress. These compounds, which are present in epidermal and hypodermal cells, filter out detrimental radiation while safeguarding the photosynthetic apparatus in the deeper tissue layers [ 68 ]. The pronounced presence of phenolic compounds in Tradescantia spathacea also signifies a formidable defence mechanism, affording antioxidant advantages that bolster the plant’s resistance to biotic and abiotic stressors [ 79 , 93 , 94 , 95 ].…”