Detecting signs of leaf aging is a step towards more perky plants, say Chinese scientists.

Da Xing and co-workers at South China Normal University in Guangzhou have developed a rapid, non-invasive way of detecting leaf senescence, the final stage of a leaf's development that leads to its death.

During senescence, breakdown of chlorophyll and chloroplasts results in leaf yellowing and a decreased photosynthesis rate. So, delaying the onset or decreasing the progression of senescence could boost crop yields and increase the value of ornamental plants. Leaf senescence can be regulated by several factors, including certain plant hormones. However, scientists must be able to accurately measure senescence before they can develop ways of delaying it.

Xing's team showed that the extent of senescence correlates with the intensity of a leaf property called intrinsic delayed fluorescence - the light emitted by a leaf some time after its exposure to visible radiation. The team has developed a biosensor that exploits this correlation to measure senescence extent in plants. The device has proved less sensitive to environmental interferences, such as humidity or heat, than most commercially-available instruments.

'The biosensor has shown tremendous potential for use in the study of the effects of salt stress, heat stress, herbicide toxicity, UV-B radiation and acid rain pollution on plant growth and development,' said Xing. The sensor is also portable, low cost and simple to use, 'making it extremely suitable for practical applications,' he said.

Freya Mearns