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 su rface 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 t o red. PAM fluorometry was used to measure changes in photosynthetic c ompetency in whole green bell peppers. Three photosynthetic characteri stics could be measured by this method: quantum yield (Fm/Fo), photoch emical quenching (Qp), and nonphotochemical quenching (Qnp). Fm/Fo dec reased 90% during the first week of storage at 2C and remained low the reafter, while Qnp decreased after 2 weeks at 2C, just before the pepp ers 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 gre en peppers.