Balancing act: Nitrogen and potassium key to boosting apple photosynthesis
image: A hypothetical model for regulating photosynthesis of apple rootstock leaves by N/K balance.
Credit: Horticulture Research
Nitrogen and potassium are fundamental nutrients for plant growth, but imbalances frequently disrupt agricultural systems. In apple orchards, low potassium can severely limit carbon and nitrogen metabolism, impairing photosynthesis and yield. Potassium availability is often reduced by environmental factors such as soil leaching, while nitrogen is frequently over-applied due to its affordability and yield-enhancing effects. Given these challenges, optimizing nitrogen and potassium levels in apple trees warrants further research to counter the negative impact of nutrient imbalances on plant health and productivity.
A team from Shandong Agricultural University and Yantai Academy of Agricultural Sciences published findings (DOI: 10.1093/hr/uhad253) on November 27, 2023, in Horticulture Research. Their research examines how varying nitrogen and potassium levels influence photosynthesis in apple rootstocks. Utilizing hydroponic setups, the study tested different Nitrogen (N) - potassium (K) ratios to assess their effects on growth. The results highlight that balanced nutrient levels are critical for maximizing photosynthetic efficiency and reducing potassium-deficiency impacts on leaf metabolism, offering potential benefits for apple orchards struggling with nutrient imbalance.
Using hydroponic systems with controlled N-K concentrations, researchers analyzed the physiological and biochemical responses in apple rootstock leaves. Low potassium conditions markedly suppressed root and leaf growth, with high nitrogen exacerbating potassium deficiency symptoms. Balanced N-K conditions optimized leaf nitrogen allocation towards photosynthetic functions, boosting electron transport, carboxylation, and overall photosynthesis. Conversely, high nitrogen in low potassium conditions increased non-photosynthetic nitrogen forms, such as cell wall proteins, which impeded CO₂ diffusion and reduced mesophyll conductance. One of the study’s highlights is the discovery that balanced N-K ratios reduce cell wall thickness in leaves, enhancing CO₂ entry and photosynthetic efficiency. Adjustments in nitrogen allocation further improved photosynthetic nitrogen use efficiency (PNUE). These findings underscore the intricate interplay between nitrogen and potassium in apple rootstocks, suggesting that balanced nutrient strategies could enhance resilience and productivity, particularly for China’s extensive apple industry.
"Maintaining a balanced nitrogen-potassium ratio is essential not only for the photosynthetic efficiency of apple trees but also for overall tree health and productivity," noted Dr. Xinxiang Xu, the study’s lead author. "Our findings suggest that many potassium deficiency issues in apple orchards can be mitigated with a targeted approach to N and K levels. This research underscores the need for continued exploration of nutrient interactions and offers practical insights that could boost crop quality and reduce nutrient waste in apple cultivation."
This study provides valuable insights into nutrient management in apple trees, suggesting a pathway to boost photosynthesis and yield by fine-tuning nitrogen and potassium ratios. By implementing balanced N-K nutrition, apple growers may see improved crop health and resilience, particularly in areas prone to nutrient imbalances. Moreover, the findings could guide sustainable fertilization practices, curbing excessive nitrogen use and bringing environmental and economic benefits. Further research on nutrient optimization across various fruit trees could extend these advantages to the wider agricultural sector.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhad253
Funding information
This work was supported bythe National Key R & D Program of China (2023YFD2301000), the Special Fund for the Natural Science Foundation of Shandong Province (ZR2021MC093), the earmarked fund for CARS (CARS-27), the Taishan Scholar Assistance Program from Shandong Provincial Government (TSPD20181206), and Xinlianxin Innovation Center for Efficient Use of Nitrogen Fertilizer (2020-apple).
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.