Light and electron microscopy aspects of the glandular sessile hairs from the vitroplantlet leave of Drosera rotundifolia

Abstract

Carnivore plants, named by Darwin (1835) insectivores [2], show morphoanatomical characteristics which allow them to capture — through different types and structures of traps — small animals, and they compensate in this way the lack of nitrogen compounds in their growth substrate. One of the carnivore plant species is Drosera rotundifolia. On the leaf of this plant we can describe a diversity of hairs. Among these, the most numerous are the tentacular, bludgeon hairs, with a very complex role. In nature, the apex of Drosera’s tentacular hairs produces some dew-like drops. These drops attract and immobilize small insects, by curving the tentacular hairs over the “prey”. In this case, the leaf’s lamina is also curving. The external cells of the bludgeon secrete proteolytic enzymes that produce protein hydrolysis. Afterwards, the amino acids that result from the proteolysis of captured insect are absorbed in the leaf’s laminar tissues. When the digestion products are depleted, the leaf and the tentacular hairs will retract in the normal position. The leaves are capable to repeat this process only for three or four times, and after that, they become senescent and die. The new leaves, after tissue differentiation, will develop this type of nutrition, in addition to photoautotrophic assimilation.