@bobmuscarella.bsky.social @svs-plant-geog.bsky.social @jxbotany.bsky.social

Relationship between PSII chlorophyll fluorescence thermal thresholds (T5 ) against thermal optima of CO2 assimilation rate (Topt,anet) measured during the warm summer period on tree species in a central Western Ghats forest in India. Relationships show linear mixed-effects models with species as random effect, P-values are for the parameters fitted, and R2 are pseudo R2 for the fits. Dotted lines indicate 95% confidence intervals for the fit. Standard major axis regression R² = 0.16, P = 0.022.

We took advantage of the microclimate gradient & measured photosynthetic temperature response & PSII thermal tolerance. We find a significant negative relationship. This could suggest a trade-off between investing resources to achieve higher Topt & maintaining PSII heat stability 3/3

Schematic depicting the distribution of the tree species studied in the Western Ghats, India. Rectangles on the left indicate the relative change in irradiance level, water availability, tree density, and soil depth from hilltops to valley areas. Codes for the species are as follows: Terminalia paniculata (TP), Terminalia chebula (TC), Careya arborea (CA), Psydrax dicoccos (PD), Tetrapilus dioicus (TD), Memecylon umbellatum (MU), Symplocos racemosa var. racemosa (SR), Hopea ponga var. ponga (HP), Knema attenuata (KA), Garcinia cambogioides var. cambogioides (GC), and Garcinia gummi-gutta (GG).

We studied 11 trees spp. across hilltop–slope–valley #thermal gradients (summer peaks: 46.1°C, 40.1°C, 31.8°C) measuring photosynthetic temperature responses and #photosystemII (PSII) T5 (5% impairment) at peak summer. 2/3

Schematic illustrating contrasting resource allocation strategies between CO2 assimilation and PSII heat tolerance. (A) CO2 assimilation is prioritized over PSII heat stability and (B) PSII heat stability is prioritized over CO2 assimilation. (C) Temperature response curves for CO2 assimilation and PSII quantum yield for two species exhibiting contrasting responses, as presented in Fig. 4C. The schematic highlights shifts in ATP and NADPH investment between PSII maintenance and Rubisco activation energy. The large curved arrow indicates the direction of resource allocation involving ATP, NADPH, and the energetic costs of D1 and turnover of other proteins. Red colour represents higher temperatures, whereas blue indicates lower temperatures

#Tropical #trees can't simultaneously raise photosynthetic heat optima AND PSII stability: resource trade-off! Inverse Topt, Anet-T5 link in #WesternGhats warns of #warming limits #PlantPhys #Climate #Photosynthesis #TropForRes
doi.org/10.1093/jxb/... 1/3

Large differences in photorespiration and its temperature response among temperate trees www.biorxiv.org/content/10.1101/2025.11....

Thanks to @pplplantarum.bsky.social & @florianabusch.bsky.social, we have full length versions in #Kannada and #Sanskrit
#language s
See the supplementary section:
doi.org/10.1111/ppl....
#sciencecommunication #India #WesternGhats #forest

Photosynthesis rate at thermal optima measured in situ during two time periods in a forest site in the Central Western Ghats region show distinct dry and wet period differences. - Hilltop deciduous trees: Max out photosynthesis in the wet season, conserve water in dry spells—just as expected! - Valley evergreens: Keep photosynthesis steady during wet and dry periods. - evergreens on hill slopes: Surprisingly ramp up photosynthesis during the dry period - hinting at a taste for warmth! Our findings show that coexisting tropical trees have different heat sensitivities.

Some trees thrive in heat. Our #WesternGhats #Tropical #forest #India study shows evergreen trees 🌳🌳 on hill slopes increase #photosynthesis in the dry, hot season, not the wet - indicating heat preference 🌡️🌡️
doi.org/10.1111/ppl....
@pplplantarum.bsky.social
@bobmuscarella.bsky.social

Big thanks to SVS for support, and to SWIFT Balachandra Hegde & IDSG College for organizing. Excited that some students are now part of our photorespiration field campaign! 🌱🔬 @bobmuscarella.bsky.social

Balachandra Hegde providing the overview of the forest landscape at Sayimane

Rakesh Tiwari demonstrating field photosynthesis measurements

Discussion on interpreting photosynthesis response curves

Students taking fluorescence measurement

Had a fantastic four-day workshop with masters & doctoral students from across India! Trained them on photosynthesis basics, heat sensitivity, and hands-on leaf trait measurements as part of the @svs-plant-geog.bsky.social -funded field campaign #Photosynthesis #ScienceWorkshop #SVS #FieldCampaign

Very proud and my first post here!