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• The cyanolichen Erioderma pedicellatum acclimates by various means to changed light. • Fragmentation was highest in specimens with the highest cover of apothecia. • Cyanolichen growth rate increased with the availability of base cation and light. • High viability after transplantation suggests that reintroduction can be successful. • Its success in rainforest depends on a combination of high light, humidity, and pH. This study focuses on the critically endangered Erioderma pedicellatu m, a sexually reproducing cyanolichen. The species' decline is primarily attributed to habitat loss and extinction debts. The aim is to understand the possibilities of reintroduction via transplantation on Picea abies (L.) H.Karst. and gain insights into the species' growth response to environmental gradients in its boreal rainforest habitat. The source population of E. pedicellatum found on open, sun-exposed spruce branches within a waterfall spray zone, underwent a significant environmental shift when transplanted to the rainforest. The shift induced shade acclimation, which was marked by an increased maximal photosystem II efficiency (F V /F M), reduced thallus thickness and reduced apparent electron transport rate (ETR app). However, stochastic fragmentation impacted 57 % of thalli, causing significant losses, particularly in sections with numerous apothecia, suggesting a trade-off between growth and reproduction. Unfragmented thalli with positive relative growth rate (RGR) exhibited increased growth correlated with base cation availability (high soil and bark pH) and light availability. Thalli that were already shade-adapted at the start (low ETR app at high light) displayed the fastest growth in the rainforest. The best subset regression model of unfragmented thalli accounted for 72.8 % of the variation in RGR. The reintroduction of E. pedicellatum into the boreal rainforest is possible, but challenging, given that well-lit spruce branches with high base cation availability in humid canopy layers are rare. [ABSTRACT FROM AUTHOR]

Main conclusion: During desiccation, both apparent electron transport rate (ETRapp) and photosynthetic CO2 uptake peak when external water has evaporated. External water, causing suprasaturation, weakens the strong correlation between ETRapp and CO2 uptake. Lichens are poikilohydric organisms passively regulated by ambient conditions. In theory, apparent electron transport rate (ETRapp), estimated by photosystem II yield measured in light (ΦPSII), is a proxy of photosynthetic CO2 uptake. Hydration level, however, is a complicating factor, particularly during suprasaturation that strongly reduces CO2 diffusion. Here, the cephalolichen Lobaria pulmonaria and two chlorolichens Parmelia sulcata and Xanthoria aureola were excessively hydrated before photosynthetic CO2 uptake and ΦPSII using imaging fluorescence tools were simultaneously measured while drying at 200 µmol photons m−2 s−1. CO2 uptake peaked when hydration had declined to a level equivalent to their respective internal water holding capacity (WHCinternal) i.e., the water per thallus area after blotting external water. CO2 uptake and ETRapp in all species were highly correlated at hydration levels below WHCinternal, but weaker at higher hydration (chlorolichens) or absent (cephalolichen). Yet, at a specimen level for the two chlorolichens, the correlation was strong during suprasaturation. The CO2 uptake—ETRapp relationship did not differ between measured species, but may vary between other lichens because the slope depends on cortical transmittance and fraction of electrons not used for CO2 uptake. For new lichen species, calibration of ETRapp against CO2 uptake is therefore necessary. At intrathalline scales, ΦPSII during drying initially increased along thallus margins before reaching maximum values in central portions when hydration approached WHCinternal. WHCinternal represents the optimal hydration level for lichen photosynthesis. In conclusion, ETRapp is an easily measured and reliable proxy of CO2 uptake in thalli without external water but overestimates photosynthesis during suprasaturation. [ABSTRACT FROM AUTHOR]

Alterations in light quality affect plant morphogenesis and photosynthetic responses but the effects vary significantly between species. Roses exhibit an irradiance-dependent flowering control but knowledge on light quality responses is scarce. In this study we analyzed, the responses in morphology, photosynthesis and flowering of Rosa × hybrida to different blue (B) light proportions provided by light-emitting diodes ( LED, high B 20%) and high pressure sodium ( HPS, low B 5%) lamps. There was a strong morphological and growth effect of the light sources but no significant difference in total dry matter production and flowering. HPS-grown plants had significantly higher leaf area and plant height, yet a higher dry weight proportion was allocated to leaves than stems under LED. LED plants showed 20% higher photosynthetic capacity (Amax) and higher levels of soluble carbohydrates. The increase in Amax correlated with an increase in leaf mass per unit leaf area, higher stomata conductance and CO2 exchange, total chlorophyll (Chl) content per area and Chl a/b ratio. LED-grown leaves also displayed a more sun-type leaf anatomy with more and longer palisade cells and a higher stomata frequency. Although floral initiation occurred at a higher leaf number in LED, the time to open flowers was the same under both light conditions. Thereby the study shows that a higher portion of B light is efficient in increasing photosynthesis performance per unit leaf area, enhancing growth and morphological changes in roses but does not affect the total Dry Matter ( DM) production or time to open flower. [ABSTRACT FROM AUTHOR]