Morphological and transcriptomic responses/acclimations of erect‐type submerged macrophyteHydrilla verticillataboth at low‐light exposure and light recovery phases

Abstract

Light intensity is a determinant for submerged macrophytes. Little is known about their molecular responses to low‐light exposure, despite more informative and responsive than morphological traits. For erect‐type submerged macrophytes, the stem is more crucial relative to the leaf in acclimation to low‐light stress, but receives less attention. We determined morphological and stem transcriptomic responses/acclimations of Hydrilla verticillata to extremely and mildly low light (7.2 and 36 μmol photons m−2 s−1, respectively), that is, EL and ML, with the radiation intensity of 180 μmol photons m−2 s−1 as the control. Low‐light exposure continued for 9 days, followed by a 7‐day recovery phase (180 μmol photons m−2 s−1). At the exposure phase, the low‐light treatments, in particular the EL, decreased the relative growth ratio, but induced greater height and longer stem internode distance and epidermal cell. Such responses/acclimations continued into the recovery phase, despite more or less changes in the magnitude. Transcriptome showed that the photosynthetic system was inhibited at the exposure phase, but the macrophyte adjusted hormone synthesis relating to cell division and elongation. Moreover, the EL activated cell stress responses such as DNA repair. Following light recovery, the macrophyte exhibited a strong‐light response, although energy metabolism enhanced. Especially, the EL enriched the pathways relating to anthocyanin synthesis at such phase, indicating an activation of photoprotective mechanism. Our findings suggest that negative influences of low light occur at both low‐light exposure and recovery phases, but submerged macrophytes would acclimate to light environments. Transcriptome can show molecular basis of plant responses/acclimations, including but not limited to morphology. This study establishes a bridge connecting morphological and molecular responses/acclimations.

Combining Multiple Remediation Techniques Is Effective for the Remediation of Eutrophic Flowing Water

“…Vallisneria natans is a rosette-type plant that is a widely distributed asexual clonal submerged plant with asexual divisions that are usually interconnected by stolons and an extensive clonal system that allows this species to adapt to heterogeneous environments [29]. Hydrilla vericillata is an erect-type submerged plant with a strong regeneration ability that is widely distributed in freshwater ecosystems [30]. Potamogeton maackianus is a canopy-type perennial herb with high water clarity requirements [31].…”