Summary
This controlled study examined how clary sage (Salvia sclarea L.) plants acclimate their photosynthetic apparatus when exposed to excess zinc (900 μM) combined with high light intensity. Under excess zinc stress, plants showed altered mineral uptake patterns, reduced chlorophyll, and decreased photoprotective quenching, yet paradoxically demonstrated improved photosynthetic efficiency through increased electron transport rate and PSII quantum yield, apparently mediated by elevated leaf manganese and iron content and increased singlet oxygen production.
UK applicability
The findings have limited direct applicability to UK agricultural practice, as they concern controlled indoor physiology of a Mediterranean medicinal herb rather than field crops. However, the mechanistic insights into how plants tolerate mineral toxicity whilst maintaining photosynthetic productivity under stress may inform understanding of heavy metal phytoremediation or medicinal herb cultivation under suboptimal conditions.
Key measures
Leaf Zn, Mn, Mg, and Fe accumulation (ICP-MS); chlorophyll content; non-photochemical quenching (NPQ); maximum efficiency of photosystem II (Fv/Fm); oxygen-evolving complex efficiency; electron transport rate (ETR); quantum yield of non-regulated energy loss (ΦNO); excess excitation energy (EXC); quantum yield of PSII photochemistry (ΦPSII); singlet oxygen (1O2) production
Outcomes reported
The study measured leaf elemental composition (Zn, Mn, Mg, Fe), chlorophyll content, and photosystem II photochemistry parameters under excess zinc exposure and high light stress in clary sage plants. Findings indicated improved photosynthetic efficiency and altered photoprotective mechanisms despite zinc toxicity stress.
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