Abstract Detail

Anatomy and Morphology

Liu, Jian-Wei [1], Li, Shau-Fu [1], Wu, Yeh-Hua [2], Wu, Chin-Ting [3], Valdespino, Iván A. [4], Chang, Ho-Ming [5], Kao, Mei-Fang [6], Chesson, Clive [7], Das, Sauren [8], Oppenheimer, Hank [9], Bakutis, Ane [10], Saenger, Peter [11], Salazar Allen, Noris [12], Yong, Jean W. H. [13], Adjie, Bayu [14], Kiew, Ruth [15], Nadkarni, Nalini [16], Ku, Maurice S. B. [17], Huang, Chun-Lin [18], Chesson, Peter [19], Sheue, Chiou-Rong [20].

Bizonoplasts, unique giant chloroplasts of the ancient vascular plant Selaginella: occurrence, variation and adaptive significance.

A unique giant chloroplast (monoplastid), the bizonoplast (Bp), has been reported recently from the dorsal epidermal cells of the vascular plant genus Selaginella (Selaginellaceae). Bps are uniquely dimorphic in ultrastructure: the upper zone contains a regular lamellar structure of thylakoids while the lower zone is occupied by both grana and stromal thylakoids. This study systematically explored the occurrence, structural variants, environmental correlates and phylogeny of the various chloroplast types in this diverse family with a view to understanding Bp adaptive significance. Chloroplast ultrastructures of 75 Selaginella species collected worldwide (7 subgenera) were observed with transmission electron microscopy. Environmental data of selected species were recorded. Based on the presence of monoplastidy (M) and chloroplast number in dorsal epidermal cells, five chloroplast categories were delineated: ME (M in a dorsal epidermal cell), MM (M in a mesophyll cell), OL (oligoplastidy (2–8/ cell), Mu (multiplastidy, > 10/ cell) and RC (reduced or vestigial chloroplast). In total, 10 shade adapted species with ME chloroplasts were found to have Bps (ME), but none from the species with MM chloroplasts. All 10 species with Bps belong to the subgenus Stachygynandrum but come from both the Old World and the New World. Moreover, two forms of Bps are recognized: cup-shaped (5 species) and bilobed (5 species). A bilobed Bp is first reported here. It is similar in shape to a bivalve shell with two lobes connected narrowly at the base. Each lobe has an upper zone at the apex, which travels down the interior side of the lobe thinning until it disappears. Both forms of Bps have similar ultrastructure, but species differ in the number of layers in the upper zone. Paradermal sections create concentric or spiral patterns resembling fingerprints in the upper zone of Bps, similar to paradermal sections of the lamelloplasts of Begoniaceae. The most basal species of Selaginella have Mu chloroplasts suggesting that M and Bps are derived traits in this ancient family. Bps are only known from deep-shade adapted (c. 0.5–2.4% full sunlight) and dorsiventral Selaginella with ME and anisophylls, in agreement with other evidence that the upper zone with regular lamellar structure is an adaptation to deep shade environments. It is highly likely that the prevalence of Bps in Selaginellaceae is higher than our current understanding. The lamellar upper zone above a giant chloroplast is an interesting photonic and photosynthetic system that requires further multidisciplinary exploration.

1 - National Chung Hsing University, 250, Kuo Kuang Rd, Taichung, N/A = Not Applicable, 402, Taiwan
2 - National Chiayi University, Department of Biological Resources, Chiayi, N/A = Not Applicable, 600, Taiwan
3 - National Chiayi University, Department of Biological Resources, Chiayi, N/A = Not Applicable, 402, Taiwan
4 - Universidad de Panamá, Departamento de Botánica, Panama, Panama
5 - Endemic Species Research Institute, Taiwan
6 - National Taiwan University, TAI Herbarium, Taipei, Taiwan
7 - 6 Barker Way, Valley View, Adelaide, Australia
8 - Indian Statistical Institute, Agricultural and Ecological Research Unit, India
9 - Maui Nui Plant Extinction Prevention Program, Maui, Hawaii, USA
10 - Molokai Plant Extinction Prevention Program, Molokai, Hawaii, USA
11 - Southern Cross University, Centre for Coastal Management, Australia
12 - Smithsonian Tropical Research Institute, Panama, USA
13 - Swedish University of Agricultural Sciences, Department of Biosystems and Technology, Alnarp, Sweden
14 - Bali Botanic Garden, Indonesia
15 - Forest Research Institute Malaysia, Kepong, Malaysia
16 - University of Utah, Department of Biology, USA
17 - National Chiayi University, Department of BioAgricultural Sciences, Chiayi, Taiwan
18 - National Museum of Natural Science, Taichung, N/A = Not Applicable, Taiwan
19 - University of Arizona, Ecology and Evolutionary Biology, Lowell St, Tucson, AZ, 85721, USA
20 - National Chung Hsing University, Dep. Of Life Sciences, Xingda Rd., Taichung, TXG, 402, Taiwan

Keywords:
Plant Structure-Function.

Presentation Type: Oral Paper
Session: AM1, Anatomy and Morphology I
Location: San Ignacio/Starr Pass
Date: Tuesday, July 30th, 2019
Time: 8:45 AM
Number: AM1001
Abstract ID:645
Candidate for Awards:None