Physiological adaptation to irradiance in duckweeds is species and accession specific and depends on light habitat niche

Abstract

Duckweeds span 36 species of free-floating aquatic organisms with body sizes ranging from 2 mm to 10 mm, where each plant body plan is reduced to a largely leaf-like structure. As an emerging crop, their fast growth rates offer potential for cultivation in closed systems. We describe a novel UK collection derived from low light (dLL) or high light (dHL) habitats, profiled for growth, photosynthesis, and photoprotection (non-photochemical quenching, NPQ) responses. Twenty-three accessions of three Lemna species and one Spirodela polyrhiza were grown under relatively low light (LL: 100 μmol m–2 s–1) and high light (HL: 350 μmol m–2 s–1) intensities. We observed broad within- and between-species level variation in photosynthesis acclimation. Duckweeds grown under HL exhibited a lower growth rate, biomass, chlorophyll, and quantum yield of photosynthesis. In HL compared with LL, carotenoid de-epoxidation state and NPQ were higher, whilst PSII efficiency (φPSII) and Chl a:b ratios were unchanged. The dLL plants showed relatively stronger acclimation to HL compared with dHL plants, especially Lemna japonica accessions. These achieved faster growth in HL with concurrent higher carotenoid levels and NPQ, and less degradation of chlorophyll. We conclude that these data support local adaptation to the light environment in duckweed affecting acclimation in controlled conditions.

Photosystem II Tolerance to Excess Zinc Exposure and High Light Stress in Salvia sclarea L.

“…Plants have several mechanisms that permit effective acclimation to HL intensities [135,136]. Although HL can enhance photosynthesis, it can also produce injury or inactivation of photosynthetic procedures (photoinhibition), especially in combination with other stresses [137]. Previous observations have highlighted that foliar Zn application enhances photoprotective mechanisms in drought-stressed wheat plants [138], whereas excess Zn (900 µM) application in S. sclarea under LL enhanced NPQ values [3], documenting Zn's suitability for enhancing photoprotection [139].…”