Temporal variability in carbon and nitrogen stable isotopes of Strobilanthes kunthianus leaf: Its photosynthetic efficacy and water-use efficiency in a warming climate

Abstract

Carbon assimilation in plants depends on both atmospheric CO 2 uptake and internal (non-atmospheric) CO 2 . To understand this mechanism in Strobilanthes kunthianus (an endemic pleitesial plant), we studied the leaf epidermal morphology, stomatal index (SI), cystoliths, carbon and nitrogen isotopes (d 13 C leaf , d 15 N leaf ) in herbarium samples collected during the bloom in 1958, 1970 and 2018 from Munnar region, India. The leaf epidermal morphology is xerophytic characterized by long, twisted and branched trichomes obscuring stomata to restrict evapotranspiration and thereby gaseous exchange. Our study shows that the values of d 13 C leaf decreased by 4% (À26.0 to À30.0%) accompanied by a decline in d 15 N leaf (+1.6 to À0.35%) from 1958 to 2018, respectively. The depleting trend in d 13 C leaf values indicates increasing photosynthetic eDcacy along with uptake of anthropogenically Bxed nitrogen (d 15 N % 0.0%). Albeit, we did not observe any alteration in SI (in response to present day increased atmospheric CO 2 ). Estimated intrinsic water use eDciency shows a reduction from 61 to 45 lmolÁmol À1 from 1958 to 2018, respectively. Leaf epidermal morphology remained static, low d 13 C leaf suggests increased photosynthesis with the use of non-atmospheric CO 2 stored in enhanced number of cystoliths during 2018 channelized via 'Alarm Photosynthesis'. Prolonged post-monsoon rainfall and soil amendment facilitated the mineral accumulation in S. kunthianus.

Palyno–morphological and isotopic characterization of monofloral and multifloral honeys from Lucknow, India

“…The δ 13 C of flower and pollen also correlates with difference of ≤ 1.0 to 2.0‰ with the leaf samples of parent plant (Farooqui et al, 2021). Therefore, δ 13 C of bulk pollen (more likely to be preserved rather than leaf/stem in the sediments) could provide clue to pollen assemblages in the sedimentary archives where species response can vary the values significantly representing past climatic conditions and its equilibrium with the vegetation (Fardusi et al, 2016;Farooqui et al, 2021). There is a growing interest in understanding the morphology and geochemistry of pollen for climate-vegetation changes and environmental informations supported by species-level identification (Pappas et al, 2003;Julier et al, 2016;Zimmermann et al, 2016).…”

“…About 175 different species were analysed for δ 13 C in pollen, leaf and stem tissue and it was found that δ 13 C of pollen correlated strongly with the parent leaf material (Jahren, 2004). The δ 13 C of flower and pollen also correlates with difference of ≤ 1.0 to 2.0‰ with the leaf samples of parent plant (Farooqui et al, 2021). Therefore, δ 13 C of bulk pollen (more likely to be preserved rather than leaf/stem in the sediments) could provide clue to pollen assemblages in the sedimentary archives where species response can vary the values significantly representing past climatic conditions and its equilibrium with the vegetation (Fardusi et al, 2016;Farooqui et al, 2021).…”