Physiological and Biochemical Effects of Potassium Deficiency on Apple Tree Growth
Potassium (K) is an essential mineral element that supports numerous plant processes, including photosynthesis, enzyme activation, osmoregulation, and nutrient balance. This study investigated how K deficiency impacts growth, physiological performance, and carbohydrate metabolism in ‘Granny Smith’ a...
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MDPI AG
2025-01-01
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| author | Evangelia-Vasiliki Ladikou Gerasimos Daras Marco Landi Theocharis Chatzistathis Thomas Sotiropoulos Stamatis Rigas Ioannis E. Papadakis |
| author_facet | Evangelia-Vasiliki Ladikou Gerasimos Daras Marco Landi Theocharis Chatzistathis Thomas Sotiropoulos Stamatis Rigas Ioannis E. Papadakis |
| author_sort | Evangelia-Vasiliki Ladikou |
| collection | DOAJ |
| description | Potassium (K) is an essential mineral element that supports numerous plant processes, including photosynthesis, enzyme activation, osmoregulation, and nutrient balance. This study investigated how K deficiency impacts growth, physiological performance, and carbohydrate metabolism in ‘Granny Smith’ apple trees grafted onto M9 rootstock. The experimental material was cultivated hydroponically in a greenhouse under four K regimes, including 0.00, 0.75, 1.50, and 3.00 mM K, over 159 days. Deficiency symptoms such as chlorosis and necrosis were observed primarily in basal leaves. A reduced net photosynthetic rate in top and basal leaves was linked to a decreased stomatal conductance, thus limiting CO<sub>2</sub> uptake (stomatal limitations of photosynthesis). Photosynthetic pigments, including chlorophyll a, chlorophyll b, and carotenoids, were also significantly reduced in K-limited leaves. Furthermore, photochemical performance of PSII also declined under K deficiency, with lower electron transport rates, PSII efficiency, and photochemical quenching (non-stomatal limitations of photosynthesis). While the photosynthetic rate declined under K deficiency conditions, the carbohydrate metabolism remained relatively stable without significant variation in total, translocating, or non-translocating sugars. Notably, an increase in sucrose-to-hexose ratio under low K suggests changes in sugar partitioning and utilization. Biomass allocation was also affected, with a notable decrease in the shoot-to-root ratio, mainly due to increased dry weight of roots, likely reflecting an adaptive response to enhance K uptake. Our study provides valuable insights into sustainable K fertilization practices aiming to maximize photosynthetic capacity, pigment content, and biomass production. These findings emphasize the importance of considering rootstock/scion interactions in future research to enhance apple tree vigor and productivity. |
| format | Article |
| id | doaj-art-2e95e0deca144a8588e7f1f488ae3c50 |
| institution | Kabale University |
| issn | 2311-7524 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Horticulturae |
| spelling | doaj-art-2e95e0deca144a8588e7f1f488ae3c502025-01-24T13:34:34ZengMDPI AGHorticulturae2311-75242025-01-011114210.3390/horticulturae11010042Physiological and Biochemical Effects of Potassium Deficiency on Apple Tree GrowthEvangelia-Vasiliki Ladikou0Gerasimos Daras1Marco Landi2Theocharis Chatzistathis3Thomas Sotiropoulos4Stamatis Rigas5Ioannis E. Papadakis6Laboratory of Pomology, Department of Crop Science, Agricultural University of Athens, Iera Odos 75, 11855 Athens, GreeceLaboratory of Molecular Biology, Department of Biotechnology, Agricultural University of Athens, Iera Odos 75, 11855 Athens, GreeceDepartment of Agriculture, Food and Environment, Via del Borghetto 80, 56124 Pisa, ItalyHellenic Agricultural Organization (ELGO) ‘DIMITRA’, Institute of Soil and Water Resources, Thermi, 57001 Thessaloniki, GreeceDepartment of Deciduous Tree Fruit Growing, Institute of Plant Breeding and Genetic Resources, Hellenic Agricultural Organization (ELGO) ‘DIMITRA’, 11145 Naoussa, GreeceLaboratory of Molecular Biology, Department of Biotechnology, Agricultural University of Athens, Iera Odos 75, 11855 Athens, GreeceLaboratory of Pomology, Department of Crop Science, Agricultural University of Athens, Iera Odos 75, 11855 Athens, GreecePotassium (K) is an essential mineral element that supports numerous plant processes, including photosynthesis, enzyme activation, osmoregulation, and nutrient balance. This study investigated how K deficiency impacts growth, physiological performance, and carbohydrate metabolism in ‘Granny Smith’ apple trees grafted onto M9 rootstock. The experimental material was cultivated hydroponically in a greenhouse under four K regimes, including 0.00, 0.75, 1.50, and 3.00 mM K, over 159 days. Deficiency symptoms such as chlorosis and necrosis were observed primarily in basal leaves. A reduced net photosynthetic rate in top and basal leaves was linked to a decreased stomatal conductance, thus limiting CO<sub>2</sub> uptake (stomatal limitations of photosynthesis). Photosynthetic pigments, including chlorophyll a, chlorophyll b, and carotenoids, were also significantly reduced in K-limited leaves. Furthermore, photochemical performance of PSII also declined under K deficiency, with lower electron transport rates, PSII efficiency, and photochemical quenching (non-stomatal limitations of photosynthesis). While the photosynthetic rate declined under K deficiency conditions, the carbohydrate metabolism remained relatively stable without significant variation in total, translocating, or non-translocating sugars. Notably, an increase in sucrose-to-hexose ratio under low K suggests changes in sugar partitioning and utilization. Biomass allocation was also affected, with a notable decrease in the shoot-to-root ratio, mainly due to increased dry weight of roots, likely reflecting an adaptive response to enhance K uptake. Our study provides valuable insights into sustainable K fertilization practices aiming to maximize photosynthetic capacity, pigment content, and biomass production. These findings emphasize the importance of considering rootstock/scion interactions in future research to enhance apple tree vigor and productivity.https://www.mdpi.com/2311-7524/11/1/42biomass allocationcarbohydratescarotenoidschlorophyll fluorescencephotosynthesisstomatal conductance |
| spellingShingle | Evangelia-Vasiliki Ladikou Gerasimos Daras Marco Landi Theocharis Chatzistathis Thomas Sotiropoulos Stamatis Rigas Ioannis E. Papadakis Physiological and Biochemical Effects of Potassium Deficiency on Apple Tree Growth Horticulturae biomass allocation carbohydrates carotenoids chlorophyll fluorescence photosynthesis stomatal conductance |
| title | Physiological and Biochemical Effects of Potassium Deficiency on Apple Tree Growth |
| title_full | Physiological and Biochemical Effects of Potassium Deficiency on Apple Tree Growth |
| title_fullStr | Physiological and Biochemical Effects of Potassium Deficiency on Apple Tree Growth |
| title_full_unstemmed | Physiological and Biochemical Effects of Potassium Deficiency on Apple Tree Growth |
| title_short | Physiological and Biochemical Effects of Potassium Deficiency on Apple Tree Growth |
| title_sort | physiological and biochemical effects of potassium deficiency on apple tree growth |
| topic | biomass allocation carbohydrates carotenoids chlorophyll fluorescence photosynthesis stomatal conductance |
| url | https://www.mdpi.com/2311-7524/11/1/42 |
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