Details

Autor(en) / Beteiligte

• Horiguchi, Genki
• Nemoto, Kyosuke
• Yokoyama, Tomomi
• Hirotsu, Naoki

Titel

Photosynthetic acclimation of terrestrial and submerged leaves in the amphibious plant Hygrophila difformis

Ist Teil von

• AoB plants, 2019-04, Vol.11 (2), p.plz009-plz009

Ort / Verlag

US: Oxford University Press

Erscheinungsjahr

2019

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Abstract Hygrophila difformis, a heterophyllous amphibious plant, develops serrated or dissected leaves when grown in terrestrial or submerged conditions, respectively. In this study, we tested whether submerged leaves and ethylene-induced leaves of the heterophyllous, amphibious plant H. difformis have improved photosynthetic ability under submerged conditions. Also, we investigated how this amphibious plant photosynthesizes underwater and whether a HCO3− transport system is present. We have analysed leaf morphology, measured underwater photosynthetic rates and HCO3− affinity in H. difformis to determine if there are differences in acclimation ability dependent on growth conditions: terrestrial, submerged, terrestrial treated with ethylene and submerged treated with an ethylene inhibitor. Moreover, we measured time courses for changes in leaf anatomical characteristics and underwater photosynthesis in terrestrial leaves after submersion. Compared with the leaves of terrestrially grown plants, leaf thickness of submerged plants was significantly thinner. The stomatal density on the abaxial surface of submerged leaves was also reduced, and submerged plants had a significantly higher O2 evolution rate. When the leaves of terrestrially grown plants were treated with ethylene, their leaf morphology and underwater photosynthesis increased to levels comparable to those of submerged leaves. Underwater photosynthesis of terrestrial leaves was significantly higher by 5 days after submersion. In contrast, leaf morphology did not change after submergence. Submerged leaves and submerged terrestrial leaves were able to use bicarbonate but submerged terrestrial leaves had an intermediate ability to use HCO3− that was between terrestrial leaves and submerged leaves. Ethoxyzolamide, an inhibitor of intracellular carbonic anhydrase, significantly inhibited underwater photosynthesis in submerged leaves. This amphibious plant acclimates to the submerged condition by changing leaf morphology and inducing a HCO3− utilizing system, two processes that are regulated by ethylene. Angiosperms invading water from air will have faced problems of carbon supply. How does an amphibious plant grow in both terrestrial and submerged conditions? This manuscript reports on the plasticity of morphological and physiological responses to submergence in an amphibious plant, Hygrophila difformis. This amphibious plant photosynthesizes underwater by utilizing HCO3− and this ability to utilize HCO3− is switched on when it is submerged. Ethylene is involved in this submergence acclimation by changing leaf morphology and inducing HCO3− utilization.