Relationship between potassium level in petiole sap and the leaf scald and fruit quality of the 'Muscat of Alexandria' grape [Vitis vinifera]
2007
Tamura, F.(Okayama-ken. General Agriculture Center, Akaiwa (Japan). Agricultural Experiment Station) | Fujii, Y. | Muranishi, K. | Takano, K.
This study investigated the real-time diagnosis of potassium concentration in 'Muscat of Alexandria' grapes grown in a soilless culture system using perlite medium. Potassium concentration in the squeezed sap of the petiole was investigated at different growth stages. Its relations to the severity of leaf injury attributable to potassium deficiency at stage III of fruit growth and fruit quality were assessed. Potassium concentration lower than 500 mg/L in sap at veraison engenders a higher correlation between the potassium level and leaf scald severity. These signs are more severe in plants with lower potassium concentrations. There were no such signs when potassium concentrations in the sap greater than 500 mg/L. At 1000 mg/L or lower potassium concentration in the sap at veraison, a positive relationship was also observed between the potassium level and berry size. Berry size was smaller when the potassium level in the sap was less than 1000 mg/L. Even when the potassium concentration was 4000 mg/L, an extremely low sugar content, implying a lower commercial value, was not observed. Relationships between potassium concentrations in the sap at the berry set stage and leaf scald or fruit quality were not clearer than those at the veraison stage.
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