Water loss and morphological modifications in leaves during acclimatization of cork oak micropropagated plantlets

Romano, Anabela; Loução, M. A. Martins

http://hdl.handle.net/10400.1/6402

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Authors

Romano, Anabela

Loução, M. A. Martins

Abstract(s)

This study characterises some aspects of foliar anatomy of cork oak micropropagated plantlets, and rates of water loss by different types of leaves during the acclimatization period. Water loss from leaves of in vitro cultured plantlets was much higher than that of acclimatized plants or seedlings. Leaves from in vitro plantlets lost 53% of their water within the first 30 min under water stress conditions, while leaves from acclimatized plants lost 14%. Leaves of in vitro grown plants presented open stomata and collapsed guard cells, while acclimatized leaves presented closed stomata. Shade-leaf structure was observed in transverse sections of in vitro leaves, with large intercellular air spaces and a low mesophyll cell density, but with a differentiated palisade cell layer. Leaves from acclimatized plants showed a sun-leaf structure with small intercellular air spaces, high cell density and two or three palisade cell layers. During acclimatization leaf thickness increased, as well as cell compactness and differentiation. Stomatal density, stomatal aperture and guard cell protuberance decreased during the acclimatization period, while trichome density increased.