Shedding light on tea: Clocks and photosynthesis
image: Schematic illustration of the circadian clock that regulates the photosynthetic production of the tea plant. A computational model was developed to study the circadian clock control of photosynthesis using a regulatory network composed of the light-sensitive protein P, core oscillator, and photosynthetic metabolic outputs. In this model, solid lines blunt at the terminal ends represent genes exerting inhibitory effects in a negative feedback loop, while arrows indicate genes that have an activating role in the regulatory network. A lightning symbol denotes transcription activation of specific genes by light.
Credit: Horticulture Research
A new study has unveiled the profound impact of varying photoperiods on the circadian rhythm and photosynthetic efficiency of tea plants, offering a pathway to optimize cultivation practices. By examining the expression of key clock genes and photosynthesis-related genes under different light conditions—ranging from normal (12L12D) to continuous (24L), and skeleton photoperiods (6L6D and 3L3D)—the research reveals how these light cycles affect the internal biological clock and overall growth of tea plants. The results showcase significant changes in gene expression and photosynthetic parameters, shedding light on tea plants' adaptability to diverse light environments and providing a scientific foundation for improving tea yield and quality.
Tea plants, a cornerstone of global agriculture, are highly sensitive to light, a factor crucial for their growth and development. Light intensity, duration, and quality are fundamental in determining the metabolic state and overall physiological processes of these plants. Previous studies have shown that light influences the morphology, seasonal growth, and developmental stages of tea plants through photoperiodic signals. However, the specific effects of different light cycles on the circadian rhythm and photosynthetic efficiency of tea plants have remained largely unexplored. Given the challenges involved in optimizing tea yield and quality under variable light conditions, a deeper understanding of how tea plants' internal clocks adapt to these changes is essential.
A study (DOI: 10.1093/hr/uhae226) led by researchers at Nanjing Agricultural University, published in Horticulture Research on August 8, 2024, delves into how different photoperiods influence the circadian rhythm and photosynthetic efficiency of tea plants. By analyzing the expression of core clock genes (CCA1, PRR9, TOC1, ELF4) and photosynthesis-related genes (Lhcb, RbcS, atpA) under four distinct light conditions—normal light (12L12D), continuous light (24L), long skeleton photoperiod (6L6D), and short skeleton photoperiod (3L3D)—the study provides crucial insights into tea plants' adaptability to varying light environments.
The researchers employed a multifaceted approach, utilizing mathematical modeling based on differential equations to simulate gene behavior across different photoperiods and comparing this data to experimental results. The findings were striking: under continuous light (24L), core clock and photosynthesis-related genes showed a delayed peak activity, shifting by 1–2 hours. For skeleton photoperiods (6L6D and 3L3D), significant changes were observed in gene expression, including altered cycles and phase shifts in core clock genes. Photosynthetic parameters, such as net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO₂ concentration (C), and transpiration rate (Tr), varied under different photoperiods. For example, Pn peaked earlier and exhibited multiple peaks under 3L3D conditions, while Gs remained stable across all treatments. These findings highlight the adaptability of tea plants' circadian clocks to diverse light conditions and reveal the mechanisms that regulate photosynthesis in response to light cycles.
Dr. Jing Zhuang, a leading researcher from Nanjing Agricultural University, underscored the importance of the study's findings, stating, "Our research provides essential insights into how tea plants adjust their physiological functions under varying light conditions. This knowledge is crucial for refining cultivation practices to enhance both yield and quality."
The implications of this study are far-reaching. By fine-tuning light cycles and intensity, tea growers could improve photosynthetic efficiency and overall tea quality. Future studies could explore the effects of long-day and short-day conditions to further investigate the adaptability of tea plants to natural light cycles. Additionally, the findings open the door to developing new tea varieties that are better equipped to thrive under changing environmental conditions, ensuring the resilience of tea cultivation in the face of global challenges.
###
References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae226
Funding information
The research was supported by the National Natural Science Foundation of China (31870681), the Provincial Policy Guidance Program North Jiangsu Science and Technology Special Project (SZ-LYG202126), Collection and Creation of Horticultural Crop Germplasm Resources of Jiangsu (JSFEM-202212), and the Priority Academic Program Development of Jiangsu Higher Education Institutions Project (PAPD).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2022. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.