engleski

Morphology na ultrastructure of Mammillaria gracillis Pfeiff. (Cactaceae) in in vitro culture

As plants with Crassulacean Acid Metabolism (CAM), cacti are highly affected by artificial environment in in vitro tissue culture. Micropropagated Mammillaria gracillis plants developed abundant callus masses without any exogenous growth regulators. This habituated (hormone independent) callus regenerated morphologically normal shoots that easily rooted, as well as hyperhydric, malformed shoots. Only few reports related to ultrastructural changes of plant cells caused by in vitro stress conditions have been published. The information on the fine structure of Mammillaria gracillis tissues has been completely lacking. We studied the morphogenetic status of Mammillaria tissue in the culture by light and electron microscopy and tried to find a correlation to tissue pigment content. Elongated and giant chloroplasts, chloroamyloplasts, secondary dedifferentiated (proplastid-like) plastids and plastids with irregular tylakoids arrangement were observed. Parenchyma cells of in vitro grown shoots had large nuclei with deep invaginations of nuclear envelope. The ratio of chlorophyll a to b was lower in the callus than in shoots, being extremely low in transformed tissues. Our results showed that plastids very sensitively react to both stress conditions in in vitro culture and to Agrobacteria mediated cell transformation.

nije evidentirano

nije evidentirano