Changes in chlorophyll fluorescence during injury in saintpaulia leaf.

<p>Solid lines show quantum yield of PS II (øII; <i>closed circles</i>) and non-photochemical quenching (NPQ; <i>open circles</i>), while broken lines indicate leaf temperature. These indices were measured during a rapid temperature decrease from 25°C to 15°C followed by rewarming to 25°C (A), during a gradual decrease from 25°C to 5°C (B), during a rapid decrease from 25°C to 5°C and kept at 5°C for 300 s followed by rewarming to 25°C (C), and during a rapid decrease from 25°C to 5°C and kept at 5°C for 30 s followed by rewarming to 25°C (D).