DETERMINING CHILLING INJURY INDUCTION IN GREEN-PEPPERS USING NONDESTRUCTIVE PULSE AMPLITUDE-MODULATED (PAM) FLUOROMETRY

Storing 'Maor' green bell peppers (Capsicum annuum L.) for 3 weeks at 2C resulted in the development of chilling injury (CI) evidenced as surface pitting. Fruit held at 8C did not develop any CI symptoms, but, after 3 weeks of storage, the fruit began to change color from green to red. PAM fluorometry was used to measure changes in photosynthetic competency in whole green bell peppers. Three photosynthetic characteristics could be measured by this method: quantum yield (Fm/Fo), photochemical quenching (Qp), and nonphotochemical quenching (Qnp). Fm/Fo decreased 90% during the first week of storage at 2C and remained low thereafter, while Qnp decreased after 2 weeks at 2C, just before the peppers began to develop CI. Qp was similar at both storage temperatures. Potassium leakage as a CI measurement also increased in excised pepper discs after 2 weeks at 2C. The results indicate that PAM fluorometry can measure CI nondestructively before tissue damage is visible in green peppers.