Mitochondrial Metabolic Shifts in Fleshy Fruits during Kiwifruit Post-Harvest Senescence.

* *Mitochondrial Metabolic Shifts in Fleshy Fruits during Kiwifruit Post-Harvest Senescence**

* *Abstract**

Post-harvest senescence in fleshy fruits, such as kiwifruit (Actinidia deliciosa), is a complex process involving changes in mitochondrial metabolism, leading to the acceleration of senescence and abscission zone formation. In this review, we focus on the mitochondrial metabolic shifts in fleshy fruits during post-harvest senescence, with a particular emphasis on the activation of alternative respiratory pathways and the shift from oxidative phosphorylation to glycolysis. We also discuss the role of ethylene-mediated acceleration of senescence and the importance of orchard-based cultivation with integrated pest management. A comprehensive understanding of these mechanisms will allow for the development of diagnostic tools and thresholds for optimal harvesting time determination based on physiological and biochemical markers.

* *Key Findings**

1. **Mitochondrial metabolic shifts**: Post-harvest senescence in fleshy fruits is characterized by a shift from oxidative phosphorylation to glycolysis, leading to an increase in anaerobic respiration and the production of lactic acid.

2. **Activation of alternative respiratory pathways**: The activation of alternative respiratory pathways, such as the citric acid cycle and the pentose phosphate pathway, contributes to the increase in anaerobic respiration and the production of reactive oxygen species (ROS).

3. **Ethylene-mediated acceleration of senescence**: Ethylene production is a key regulator of senescence in fleshy fruits, and its levels increase during post-harvest senescence.

4. **Abscission zone formation**: The formation of the abscission zone is a critical step in the senescence process, and its regulation is influenced by ethylene and other hormones.

* *Botanical Mechanisms**

1. **Mitochondrial function**: Mitochondria play a central role in the regulation of respiration and energy production in fleshy fruits.

2. **Alternative respiratory pathways**: The activation of alternative respiratory pathways contributes to the increase in anaerobic respiration and the production of ROS.

3. **Ethylene production**: Ethylene production is a key regulator of senescence in fleshy fruits, and its levels increase during post-harvest senescence.

4. **Hormone regulation**: Hormones, such as auxins and gibberellins, play a role in the regulation of senescence and abscission zone formation.

* *Methods/Diagnostics**

1. **Measurement of respiration rates**: Respiration rates can be measured using techniques such as gas chromatography and mass spectrometry.

2. **Measurement of ethylene production**: Ethylene production can be measured using techniques such as gas chromatography and mass spectrometry.

3. **Physiological and biochemical markers**: Physiological and biochemical markers, such as pH, EC, and nutrient levels, can be used to determine optimal harvesting time.

* *Interpretation**

1. **Diagnostic thresholds**: Diagnostic thresholds for optimal harvesting time determination based on physiological and biochemical markers can be established.

2. **Practical implications**: A comprehensive understanding of the mechanisms of post-harvest senescence in fleshy fruits can be used to develop strategies for improving post-harvest storage and transportation.

* *Diagnostic Thresholds/Assay Caveats**

1. **pH threshold**: A pH threshold of 4.5-5.5 is recommended for optimal harvesting time determination.

2. **EC threshold**: An EC threshold of 2-3 dS/m is recommended for optimal harvesting time determination.

3. **Nutrient threshold**: A nutrient threshold of 1-2% N, 0.5-1% P, and 1-2% K is recommended for optimal harvesting time determination.

* *Practical Implications**

1. **Improved post-harvest storage and transportation**: A comprehensive understanding of the mechanisms of post-harvest senescence in fleshy fruits can be used to develop strategies for improving post-harvest storage and transportation.

2. **Optimal harvesting time determination**: Diagnostic thresholds for optimal harvesting time determination based on physiological and biochemical markers can be established.

* *Limitations**

1. **Complexity of post-harvest senescence**: Post-harvest senescence in fleshy fruits is a complex process involving multiple mechanisms and interactions.

2. **Variability in fruit characteristics**: Variability in fruit characteristics, such as pH, EC, and nutrient levels, can affect the accuracy of diagnostic thresholds.

* *Technical FAQ**

1. **What is the optimal pH range for kiwifruit storage?**

• The optimal pH range for kiwifruit storage is 4.5-5.5.

2. **What is the optimal EC range for kiwifruit storage?**

• The optimal EC range for kiwifruit storage is 2-3 dS/m.

3. **What is the optimal nutrient range for kiwifruit storage?**

• The optimal nutrient range for kiwifruit storage is 1-2% N, 0.5-1% P, and 1-2% K.