Yuen-Po Yang

Bizonoplast, a unique chloroplast in the epidermal cells of microphylls in the shade plant Selaginella erythropus (Selaginellaceae).

Study of the unique leaf anatomy and chloroplast structure in shade-adapted plants will aid our understanding of how plants use light efficiently in low light environments. Unusual chloroplasts in terms of size and thylakoid membrane stacking have been described previously in several deep-shade plants. In this study, a single giant cup-shaped chloroplast, termed a bizonoplast, was found in the abaxial epidermal cells of the dorsal microphylls and the adaxial epidermal cells of the ventral microphylls in the deep-shade spike moss Selaginella erythropus. Bizonoplasts are dimorphic in ultrastructure: the upper zone is occupied by numerous layers of 2-4 stacked thylakoid membranes while the lower zone contains both unstacked stromal thylakoids and thylakoid lamellae stacked in normal grana structure oriented in different directions. In contrast, other cell types in the microphylls contain chloroplasts with typical structure. This unique chloroplast has not been reported from any other species. The enlargement of epidermal cells into funnel-shaped, photosynthetic cells coupled with specific localization of a large bizonoplast in the lower part of the cells and differential modification in ultrastructure within the chloroplast may allow the plant to better adapt to low light. Further experiments are required to determine whether this shade-adapted organism derives any evolutionary or ecophysiological fitness from these unique chloroplasts.

Altitudinal variation of resin ducts in Pinus taiwanensis Hayata (Pinaceae) needles

The variation of resin ducts in needles of Pinus taiwanensis along an altitude gradient (700 m- 3,100 m) in central Taiwan is revealed for the first time in this study, including position type, number, size, arrangement pattern and anatomical structural variation. Three types of resin ducts-medial, external and septal-were found according to their relative positions in the mesophyll. All needles sampled showed combinations of these three resin duct types. Mostly, 3-7 resin ducts were found in the mesophyll per needle, and the number of resin ducts was significantly greater at mid altitudes than at high and low altitudes. Septal ducts decreased in number with an increase in altitude; however, needles from mid altitudes had more external ducts. Eight patterns (basic and patterns I-VII) of resin ducts in the mesophyll of needles were delineated to present the arrangement variations. In addition to the primary ducts found in the mesophyll, we found the rare bundle sheath ducts in some needles, and their frequencies decreased obviously with an increase in altitude. The consistent combination feature of medial, external, and septal ducts in needles of P. taiwanensis from Taiwan could be easily distinguished from those with medial ducts from mainland China. However, this difference has unrecognized before, and it should be considered in future taxonomic work.

On the morphology and molecular basis of segregation of Ceriops zippeliana and C. decandra (Rhizophoraceae) from Asia.

Ceriops zippeliana, a member of the mangrove Rhizophoraceae, was first reported in 1849. It was considered to be a synonym of C. decandra, which is still widely accepted. We present morphological and molecular evidence to show that C. zippeliana is significantly distinct from C. decandra, and illustrations and an identification key to both species.

Comparative morphology on leaves of Daphniphyllum (Daphniphyllaceae).

A comparative anatomical study on the leaves of nine out of 29 species of the genus Daphniphyllum was performed to seek support for the present infrageneric classification. Daphniphyllum is composed of two sections, Lunata (with one subsection Lunata) and Daphniphyllum (with two subsections, Daphniphyllum and Staminodia). The glabrous leaves with brachyparacytic stomata appear in all species in this study; hemiparacytic, laterocytic or anomocytic stomata occur in some taxa. Two (out of three) species of section Lunata show irregular epidermal cells with undulate anticlinal walls on both surfaces and hemiparacytic stomata. Of section Daphniphyllum seven (out of 26) species were sampled; they have curved, straight or undulate anticlinal cell walls and laterocytic or anomocytic stomata. The anatomical features found in this study are useful for identification on the specific level, but there is no support for the current infrasectional classification of section Daphniphyllum; further study on section Daphniphyllum is necessary.