SEASONAL RHYTHMICS OF THE LEUCOPLAST STRUCTURE IN BULB SCALES OF SCILLA SIBIRICA L.
E. A. Miroslavov, K. M. Barmicheva
V. L. Komarov Botanical Institute RAS, St. Petersburg, Russia;
e-mail: miroslav@kd1537.spb.edu
A study was made of seasonal changes in plastids of ground tissue cells of bulb scales in early-spring
ephemeroid Scilla sibirica L. In summer, plastids are represented by typical amyloplasts, with their main volume
(97.0 ± 4.3 %) being occupied by one large starch grain. The volume fraction of plastid stroma is at its minimum. The stroma
contains small plastoglobuli and no thylakoids. The same structure is characteristic of plastids in October. However, no starch
is found in December, when some thylakoids are seen at the plastid periphery. In the early spring (March), when leaves still
remain below the ground, the volume fraction of starch grains is 53.0 ± 2.2 %. In the stroma some structures superficially
similar to those of microtubuli are revealed. The thylakoid system is fairly well developed, some of thylakoids being
concentrically arranged. Some electron-opaque material is seen in the thylakoid lumen. Many plastids are sheathed with elements
of the smooth endoplasmic reticulum. Based on the analysis of these and literature data, a conclusion is made that plastids of
bulb scales not only store starch, but also seemingly participate in phytohormone biosynthesis.
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