Seasonal changes in the chloroplast ultrastructure of Diapensia lapponica

• Published in: Nordic Journal of Botany
• Main Author: Pihakaski, Kaarina
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1988
• Subjects: Midwinter; Northern Finland
• Online Access: http://dx.doi.org/10.1111/j.1756-1051.1988.tb00512.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1756-1051.1988.tb00512.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1756-1051.1988.tb00512.x

Leaf specimens of evergreen Diapensia lapponica were collected monthly in Northern Finland (ca 70°N) in order to study seasonal changes in the ultrastructure of the chloroplasts of the palisade mesophyll. The volume fraction of chloroplasts per cell was lowest in summer and increased towards autumn and winter. However, the relative size seemed to be higher in summer than in other seasons. Length/width (L/W) ratio was calculated as an index of the chloroplast shape. The shape varied from elongated (usually concavo‐convex in profile), with an L/W ratio from 1.9 to 2.5 in summer, to roundish or irregular (L/W ratio from 1.2 to 1.4) in midwinter. In autumn the chloroplasts were most elongated (LW ratio 2.6). The starch content was highest at the end of June when it constituted 38% of the volume of chloroplast. It decreased from then till November and was absent during the rest of the winter. Changes in the thylakoid system involved an increase in the number of partitions from an average of three in early summer to 11 in autumn and a decrease to M again towards winter. In spring it was up to 7 again. The large grana and high portion of stroma thylakoids observed in late August ‐ September (the period of rhythmic light) are consistent with the high photosynthesis activity reported previously in D. lapponica in laboratory conditions.