The role of crassulacean acid metabolism induction in plant adaptation to water deficit

2020

Physiologia Plantarum

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Previous studies of crassulacean acid metabolism (CAM) pathway during stress have been directed at individual drought and salinity stress, here, we studied the effects of a combination of drought and salt on CAM expression, chlorophyll fluorescence and antioxidant parameters in the C 3-CAM facultative Sedum album and C 4-CAM facultative Portulaca oleracea plants. While salinity alone was not able to induce functional CAM expression in P. oleracea leaves, we showed that salinity induced low level of nocturnal acid accumulation in S. album species. After 20 d of exposure to the combination of simultaneous salt and drought stress, P. oleracea plants exhibited more resistance to photoinhibition as compared to S. album plants. The decrease of maximum quantum yield (F v /F m) in S. album leaves under combined stress was in parallel with the largest suppression of CAM expression of >50%, probably displaying the withdrawal of functional CAM back to C 3 pathway. However, under drought treatment alone, S. album plants exhibited higher photosynthetic flexibility, which was associated with the up-regulation of antioxidant enzymes activities and maintenance of glutathione (GSH) pool, and consequently higher photochemical functioning. The levels of nitric oxide (NO) correlated well with CAM expression, which was observed only in S. album, suggesting that NO acts in a different way in C 3 and C 4 species during CAM induction. Additionally, in both species, over the course of CAM induction, the changes in CAM expression parameters exhibited a similar pattern to that of antioxidant capacity and photochemical functioning parameters.

Section: Discussionmentioning

confidence: 99%

“…At daytime, these organic acids are decarboxylated leading to the formation of CO 2 which is required for the Calvin cycle. Different modes of the CAM pathway have been described including constitutive or obligate CAM, facultative CAM, cycling CAM, and idling CAM (Habibi 2016, Winter et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Comparison of CAM expression, photochemistry and antioxidant responses in Sedum album and Portulaca oleracea under combined stress

2020

Physiologia Plantarum

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Changes in crassulacean acid metabolism expression, chloroplast ultrastructure, photochemical and antioxidant activity in the

2021

Funct. Plant Biol.

We determined time course changes of photochemical and antioxidant activity during the induction of strong crassulacean acid metabolism (CAM) in Aloe vera L. plants grown under salt and drought stress. We found that the strong CAM was induced during 25–30days of drought alone treatment. After 25–30days, we showed the withdrawal of strong CAM back to constitutive CAM background under the combination of simultaneous drought and salt stress, which coincided with the accumulation of malondialdehyde, and the decrease in the contents of endogenous nitric oxide (NO) and non-enzymatic antioxidants. At the same time, the chloroplast ultrastructure was damaged with a parallel accumulation of reactive oxygen species, and the whole photosynthetic electron transport flux was impaired by combined stress treatment. In conclusion, the changes in CAM expression parameters was attended by a similar pattern of antioxidant and photochemical change in Aloe plants subjected to only drought or combined stress.

Effects of mild and severe drought stress on the biomass, phenolic compounds production and photochemical activity of Aloe vera (L.) Burm.f.

2018

AAS

In this study, the biomass, compatible solutes, PSII functioning and phenolic profiles of Aloe vera (<a title="Carl Linnaeus" href="https://en.wikipedia.org/wiki/Carl_Linnaeus">L.</a>) <a title="" href="https://en.wikipedia.org/wiki/Nicolaas_Laurens_Burman">Burm.f.</a> leaves were investigated at different time intervals after drought stress (20, 40 and 80 % of the field capacity). While the impaired ability of leaves for synthesis of assimilates caused growth inhibition in A. vera under severe drought stress, we observed that the content of proline, soluble sugars, total phenolic and flavonoids tended to increase in plants treated with mild drought stress. Under mild drought stress, the increased leaf thickness correlated with the higher productivity in terms of leaf biomass and gel production. Also, mild drought stress enhanced photochemical activity in Aloe leaves, and changed the entire quantity of secondary metabolite of vanillic acid produced, which may be considered to obtain better growth and considerable secondary metabolite of the medicinal Aloe plants treated with mild drought stress.