Structural features of the leaf epidermis of Halodule uninervis

Leaf blade epidermal cells of the marine angiosperm Halodule uninervis (Forssk.) Aschers resemble transfer cells since they possess a highly invaginated plasmalemma with which numerous mitochondria are often associated. However, wall ingrowths found in transfer cells of terrestrial plants are lacking. The plasmalemma is invaginated around fibrillar material which is not continuous with the cell walls and which appears to be structurally different from cell wall material. Epidermal cells possess an organelle-rich cytoplasm in which chloroplasts and electron-dense deposits feature prominently. The outer cell wall is about twice as thick as the other walls and seems to have a porous texture. A thin but distinct cuticle covers the leaf surface. Often minute cavities occur within the cuticle adjacent to the wall. Epiphytic algae and bacteria are frequently found in close association with the epidermis. Based on structural features, it would appear that leaf blade epidermal cells of H. uninervis play an important role in the leaf’s activities such as synthesis of carbohydrates, absorption and secretion of solutes and osmoregulation. Blaarlamina-epidermisselle van die marine angiosperm Halodule uninervis (Forssk.) Aschers stem ooreen met oordragselle aangesien hulle soos laasgenoemde ook instulpings van die plasmalemma besit, wat met talryke mitochondrions geassosieer is. Die selwandingroeiings soos bekend by die oordragselle van landplante ontbreek egter. Die plasmalemma vou om instulpings van fibrillêre materiaal te vorm wat struktureel van die selwand verskil en waarskynlik nie aan die selwand geheg is nie. Die epidermisselle besit ’n organelryke sitoplasma met prominente chloroplaste en elektrondigte afsettings. Die buitenste tangensiale selwand is ongeveer twee keer so dik as die ander wande en het blykbaar n poreuse tekstuur. Die blaaroppervlak word deur ’n dun, maar opvallende kutikula bedek. Klein holtes kom dikwels in die kutikula, aangrensend aan die selwand, voor. Epifitiese alge en bakterieë kom dikwels in noue assosiasie met die epidermis voor. Op grond van strukturele kenmerke wil dit voorkom of die blaarlamina-epidermisselle van H. uninervis ’n belangrike rol in die aktiwiteite van die blaar vervul, soos die sintese van koolhidrate, absorbsie en sekresie van opgeloste stowwe en osmotiese regulering.