title: A variation on chloroplast development: the bizonoplast and photosynthetic efficiency in the deep-shade plant Selaginella erythropus.
abstract: •
  
  
  OBJECTIVE
  Chloroplast development and structure are highly conserved in vascular plants, but the bizonoplast of Selaginella is a notable exception. In the shade plant S. erythropus, each dorsal epidermal cell contains one bizonoplast, while other cells have normal chloroplasts. Our quest was to (1) determine the origin of bizonoplasts, (2) explore developmental plasticity, and (3) correlate developmental changes with photosynthetic activity to provide insights unavailable in other green plants with more constrained development.•
  
  
  METHODS
  Bizonoplast development was studied in juvenile prostrate and older erect shoots of S. erythropus. Plastid plasticity was studied in plants cultivated under different light conditions. Chlorophyll fluorescence was measured and correlated with photosynthetic activity.•
  
  
  RESULTS
  The bizonoplast originates from a proplastid, forming a distinctive upper zone rapidly after exposure to low light. In the prostrate shoots, the proplastid develops through early stages only. When the shoot becomes erect, the proplastid soon develops into a mature bizonoplast. Erect shoots have significantly higher photosynthetic efficiency than prostrate shoots. No bizonoplasts were found in the plants growing in high light, where 2-4 spheroidal chloroplasts formed, or with light from below.•
  
  
  CONCLUSIONS
  The upper zone develops above a normal-looking chloroplast structure to produce a bizonoplast. Bizonoplast developmental plasticity suggests that regular lamellar structure and monoplastidy are adaptations to deep shade environments. Such novel variation in S. erythropus is in stark contrast to known plastid development in other vascular plants, possibly reflecting retention of developmental flexibility in the basal clade, Lycophyta, to which it belongs.
authors: Department of Life Sciences & Research Center for Global Change Biology, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 40227, Taiwan.
authors: Chiou-Rong
authors: CR
authors: Sheue
authors: Department of Life Sciences & Research Center for Global Change Biology, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 40227, Taiwan.
authors: Jian-Wei
authors: JW
authors: Liu
authors: Department of Life Sciences & Research Center for Global Change Biology, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 40227, Taiwan.
authors: Jia-Fang
authors: JF
authors: Ho
authors: Department of Biological Resources, National Chiayi University, 300 Syuefu Rd., Chiayi 60004, Taiwan.
authors: Ai-Wen
authors: AW
authors: Yao
authors: Department of Life Sciences & Research Center for Global Change Biology, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 40227, Taiwan Department of Biological Resources, National Chiayi University, 300 Syuefu Rd., Chiayi 60004, Taiwan.
authors: Yeh-Hua
authors: YH
authors: Wu
authors: Agricultural and Ecological Research Unit, Indian Statistical Institute, 203 Barrackpore Trunk Rd., Kolkata 700108, India.
authors: Sauren
authors: S
authors: Das
authors: Kaohsiung District Agricultural Research and Extension Station, 2-6 Dehe Rd., Changjhih Township, Pingtung County 90846, Taiwan.
authors: Chi-Chu
authors: CC
authors: Tsai
authors: Institute of Plant and Microbial Biology, Academia Sinica, 128 Academia Rd., Sec. 2, Nankang, Taipei 11529, Taiwan.
authors: Hsiu-An
authors: HA
authors: Chu
authors: Department of Bioagricultural Science, National Chiayi University, 300 Syuefu Rd., Chiayi 60004, Taiwan.
authors: Maurice S B
authors: MS
authors: Ku
authors: Department of Life Sciences & Research Center for Global Change Biology, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 40227, Taiwan Department of Ecology and Evolutionary Biology, The University of Arizona, Tucson, Arizona 85721 USA.
authors: Peter
authors: P
authors: Chesson
mesh_terms: D000222:Adaptation, Physiological; D002736:Chloroplasts / Q000378:metabolism*; D008027:Light; D010788:Photosynthesis; D032503:Selaginellaceae / Q000166:cytology / Q000378:metabolism*
keywords: Selaginellaceae; cup-shaped; erect shoot; microphyll; monoplastidy; photosynthesis; plasticity; plastid; ultrastructure; upper zone