Abstract
Leaf senescence, accompanied by chlorophyll breakdown, chloroplast degradation and inhibition of photosynthesis, can be suppressed by an exogenous application of cytokinins. Two aromatic cytokinin arabinosides (6-benzylamino-9-β-d-arabinofuranosylpurines; BAPAs), 3-hydroxy- (3OHBAPA) and 3-methoxy- (3MeOBAPA) derivatives, have recently been found to possess high anti-senescence activity. Interestingly, their effect on the maintenance of chlorophyll content and maximal quantum yield of photosystem II (PSII) in detached dark-adapted leaves differed quantitatively in wheat (Triticum aestivum L. cv. Aranka) and Arabidopsis (Arabidopsis thaliana L. (Col-0)). In this work, we have found that the anti-senescence effects of 3OHBAPA and 3MeOBAPA in wheat and Arabidopsis also differ in other parameters, including the maintenance of carotenoid content and chloroplasts, rate of reduction of primary electron acceptor of PSII (QA) as well as electron transport behind QA, and partitioning of absorbed light energy in light-adapted leaves. In wheat, 3OHBAPA had a higher protective effect than 3MeOBAPA, whereas in Arabidopsis, 3MeOBAPA was the more efficient derivative. We have found that the different anti-senescent activity of 3OHBAPA and 3MeOBAPA was coupled to different ethylene production in the treated leaves: the lower the ethylene production, the higher the anti-senescence activity. 3OHBAPA and 3MeOBAPA also efficiently protected the senescing leaves of wheat and Arabidopsis against oxidative damage induced by both H2O2 and high-light treatment, which could also be connected with the low level of ethylene production.
Highlights
Phytohormones cytokinins (CKs) have a crucial role in almost all stages of plant growth and development, including senescence
In line with our previous results [26], the decline in Chl content was more pronounced in the case of Arabidopsis leaves, which reflected a higher progression of senescence compared to wheat (Figure 2A)
The relative rate of degradation of Chl a and Chl b differed between the leaves of wheat and Arabidopsis, as evidenced by different changes in the Chl a/b ratio (Figure 2B)
Summary
Phytohormones cytokinins (CKs) have a crucial role in almost all stages of plant growth and development, including senescence. A comparison of the anti-senescence activity of of two selected BAPAs, 3-hydroxy- (3OHBAPA) and 3-methoxy- (3MeOBAPA) derivatives (see Figure 1), two selected BAPAs, 3-hydroxy- (3OHBAPA) and 3-methoxy- (3MeOBAPA) derivatives We have investigated whether the different effects of 3OHBAPA and 3MeOBAPA on the senescence of detached wheat We have explored the that the different anti-senescent activity of 3OHBAPA and 3MeOBAPA in both plant models is related. We have evaluated whether 3OHBAPA and 3MeOBAPA can protect senescing leaves of wheat and Arabidopsis against oxidative damage induced by both H2 O2 and high-light treatment
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