Abstract
Higher plants display different adaptive strategies in photosynthesis to cope with abiotic stress. In this study, photosynthetic mechanisms and water relationships displayed byJatropha curcasL. (physic nuts) andRicinus communisL. (castor bean), in response to variations in environmental conditions, were assessed.R. communis showed higher CO2 assimilation, stomatal and mesophyll conductance thanJ. curcas as light intensity and intercellular CO2 pressure increased. On the other hand,R. communis was less effective in stomatal control in response to adverse environmental factors such as high temperature, water deficit and vapor pressure deficit, indicating lower water use efficiency. Conversely,J. curcas exhibited higher photosynthetic efficiency (gas exchange and photochemistry) and water use efficiency under these adverse environmental conditions.R. communisdisplayed higher potential photosynthesis, but exhibited a lowerin vivo Rubisco carboxylation rate (Vcmax) and maximum electron transport rate (Jmax). During the course of a typical day, in a semiarid environment, with high irradiation, high temperature and high vapor pressure deficit, but exposed to well-watered conditions, the two studied species presented similar photosynthesis. Losing potential photosynthesis, but maintaining favorable water status and increasing non-photochemical quenching to avoid photoinhibition, are important acclimation mechanisms developed byJ. curcas to cope with dry and hot conditions. We suggest thatJ. curcas is more tolerant to hot and dry environments thanR. communis but the latter species displays higher photosynthetic efficiency under well-watered and non-stressful conditions.
Highlights
Photosynthetic performance in higher plants under adverse environmental conditions is largely dependent on plant species, which are able to trigger distinct adaptive mechanisms to deal with specific stressful conditions (Cousins et al, 2014)
In order to compare the photosynthetic characteristics of J. curcas and R. communis plants in response to adequate and stressful environmental conditions, we performed a set of individual experiments
Jatropha curcas and Ricinus communis photosynthetic efficiency ally, we reproduced the conditions of seasonal variation in the major parameters of photosystem II (PSII) and gas exchange and made evaluations over a typical day in a semiarid region
Summary
Photosynthetic performance in higher plants under adverse environmental conditions is largely dependent on plant species, which are able to trigger distinct adaptive mechanisms to deal with specific stressful conditions (Cousins et al, 2014). Plants display a set of acclimation strategies to maintain adequate photosynthesis rates in response to abiotic stress-inducers such as high temperature, drought and high light levels (Liu and Huang 2008; Chaves et al, 2009; Gonzalez-Cruz and Pastenes, 2012) To reach their potential or maximum photosynthesis, plants employ a fine metabolic coordination involving several inter-related processes, especially a close balance between photochemical activity and Calvin cycle reactions (Goh at al., 2012). Native species are able to survive under stressful environment conditions These organisms are an important source of genes involved in stress tolerance and models for elucidating the steps that result in the limitation of photosynthesis efficiency. This feature is more relevant when these native plants have great agronomical potential like Jatropha curcas L. (physic nuts), a biofuel source of high quality (Achten et al, 2010)
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