A team of scientists from the University of Southampton are turning Boy Scout in a bid to discover how to prevent lettuces from going limp.

The team, from the University Plants and Environment laboratory, have been camping in fields overnight to discover whether by changing the time lettuces are harvested, their shelf life and quality can be improved. Every four hours for a 24-hour period they will harvest a sample of baby leaf Lollo Rosso and Roquette varieties, which will then be processed and analysed to see if some remain fresher for longer.

Leading the study, Dr Gail Taylor explained to BBC news online that the biggest clue so far to longevity is the rigidity of the leaf's cell walls. Taylor explained: "The plant cell wall is a complex structure with many different types of molecule that form a network capable of shrinking and stretching, to regulate cell volume."

This molecular movement is in part determined by the time of day and there is "some good evidence that if you harvest salad at night it is of a better quality and will last longer in the supermarket".

Taylor explained that this is because: "During the day, photosynthesis ensures there is a build up of sugars which appear to be important in producing a good quality leaf." Meanwhile there is "reduced water loss in the evening as stomata in the leaves close to prevent transpiration".

The scientific study in Winchester is part of a three-year research programme funded by Vitacress Salads, which hopes to discover how to improve the ability of lettuce leaves to withstand the process of washing, drying and packing.