Hydathode Structure of Micropropagated Plantlets and Greenhouse-grown ‘Totem’ Strawberry Plants

Abstract

Leaves of in vitro-grown plantlets and greenhouse-grown plants of ‘Totem’ strawberry ( Fragaria × ananassa Duch.) were compared using scanning and light microscopy. Each apex and marginal serration of in vitro- and greenhouse-grown leaves had a terminal hydathode region. The leaf teeth were composed of an acuminate-mucronate tip, obscured in greenhouse-grown plants by an abaxial cluster of thick-walled unicellular trichomes, and a subterminal, adaxial group of sunken water pores. Water pores and stomata of plantlet leaves were open, whereas greenhouse-grown plant leaves had closed water pores and stomata or comparatively small apertures. Internally, the hydathodes of greenhouse-grown plants and cultured plantlets were delimited by a bundle sheath that extended below the vascular tissues, approaching the adaxial epidermis on each side of the zone of water pores. Between the epidermis and the vascular tissues were loosely arranged epithem cells. The hydathodes of plantlet leaves were smaller than greenhouse-grown plants, with fewer water pores and reduced epithem.