Abstract:

Using ultrathin section and transmission electron microscopy,the developmental process of oil and mucilage cells in Cinnamomum longepaniculatum was observed.According to the development of three wall layers,the process can be divided into 4 stages.In stage 1,the cell wall is consist only of primary (the out) cellulose layer.This stage can also be divided into two periods:one of which is oil cell initial and another is vacuolizing oil cell.During this stage,there are some small electron translucent vesicles and quite different size dark osmiophilic drops in different shaped plastids.Similarly,there also exist dark and gray osmiophilic materials in ground cytoplasm,and their coalescence with vacuoles was observed too.In stage 2,suberized layer is present,and the lamellated suberin layer accumulates inside the primary cellulose layer.In stage 3,the inner cellulose wall layer is formed.Thicker and looser inner cellulose wall layer is piled up gradually inside the suberin layer.In this stage,because of the accumulation of a great quantity of osmiophilic material,the big vacuole becomes into an oil sac filled with osmiophilic lipophilic substances.In stage 4,oil cell matures and the cytoplasm disintegrates.After oil cell maturity,the ground cytoplasm starts to disintegrate,and becomes more electron opaque or exhibits a disordered state.Oil sac is enveloped by plasmalemma and attached to the cupule,which is formed by the protuberance of inner cellulose wall layer into the lumen.Mucilage cells come from parts of oil cells.There are two developmental patterns.One is that mucilage cell comes from oil cell whose inner cellulose layer has already formed.In the ground cytoplasm of such an oil cell,some multimembrane structures whose membrane arranged like concentric circles or like a spiral come out gradually and fill up the whole lumen.Finally,the multimembrane structures disintegrate and become into filiform or granular mucilage.Another pattern is that mucilage cell comes from fully matured oil cell,whose cytoplasm has already disintegrated.In such an oil sac,osmiophilic oil shows an inhomogeneous state.Many local disintegrative sites take place in the different electronic density oil,and these sites expand gradually.Finally,oil disintegrated completely into filiform or granular mucilage.This studies on the developmental ultrastructure of oil and mucilage cells verified that mucilage cell comes from oil cell.

Key words: Cinnamomum longepaniculatum, Oil cells, Mucilage cells, Development, Ultrastructure, Suberin layer