AUTHOR=Sakoda Kazuma , Yamori Wataru , Shimada Tomoo , Sugano Shigeo S. , Hara-Nishimura Ikuko , Tanaka Yu 

TITLE=Higher Stomatal Density Improves Photosynthetic Induction and Biomass Production in Arabidopsis Under Fluctuating Light

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.589603

DOI=10.3389/fpls.2020.589603

ISSN=1664-462X

ABSTRACT=<p>Stomatal density (<italic>SD</italic>) is closely associated with photosynthetic and growth characteristics in plants. In the field, light intensity can fluctuate drastically within a day. The objective of the present study is to examine how higher <italic>SD</italic> affects stomatal conductance (<italic>g</italic><sub><italic>s</italic></sub>) and CO<sub>2</sub> assimilation rate (<italic>A</italic>) dynamics, biomass production and water use under fluctuating light. Here, we compared the photosynthetic and growth characteristics under constant and fluctuating light among three lines of <italic>Arabidopsis thaliana</italic> (L.): the wild type (WT), <italic>STOMAGEN/EPFL9</italic>-overexpressing line (ST-OX), and <italic>EPIDERMAL PATTERNING FACTOR 1</italic> knockout line (<italic>epf1</italic>). ST-OX and <italic>epf1</italic> showed 268.1 and 46.5% higher <italic>SD</italic> than WT (<italic>p</italic> &lt; 0.05). Guard cell length of ST-OX was 10.0% lower than that of WT (<italic>p</italic> &lt; 0.01). There were no significant variations in gas exchange parameters at steady state between WT and ST-OX or <italic>epf1</italic>, although these parameters tended to be higher in ST-OX and <italic>epf1</italic> than WT. On the other hand, ST-OX and <italic>epf1</italic> showed faster <italic>A</italic> induction than WT after step increase in light owing to the higher <italic>g</italic><sub><italic>s</italic></sub> under initial dark condition. In addition, ST-OX and <italic>epf1</italic> showed initially faster <italic>g</italic><sub><italic>s</italic></sub> induction and, at the later phase, slower <italic>g</italic><sub><italic>s</italic></sub> induction. Cumulative CO<sub>2</sub> assimilation in ST-OX and <italic>epf1</italic> was 57.6 and 78.8% higher than WT attributable to faster <italic>A</italic> induction with reduction of water use efficiency (<italic>WUE</italic>). <italic>epf1</italic> yielded 25.6% higher biomass than WT under fluctuating light (<italic>p</italic> &lt; 0.01). In the present study, higher <italic>SD</italic> resulted in faster photosynthetic induction owing to the higher initial <italic>g</italic><sub><italic>s</italic></sub>. <italic>epf1</italic>, with a moderate increase in <italic>SD</italic>, achieved greater biomass production than WT under fluctuating light. These results suggest that higher <italic>SD</italic> can be beneficial to improve biomass production in plants under fluctuating light conditions.</p>