Abstract
Ten doubled haploid (DH) lines of winter barley with an increased range of freezing/drought tolerance were used to identify phytohormones involved in plant stress acclimation. Cold hardening and drought stress were applied at the most critical stages of plant development on young seedlings and heading plants, respectively. The level of the phytohormones was significantly higher at heading, more than 5-fold in respect of salicylic acid (SA) and total brassinosteroids (BRs) and 1.7-fold in the case of abscisic acid (ABA). Moreover, the spectrum of detectable BRs increased from one—homocastasterone (HCS)—found in seedlings to four BRs identified in heading plants [HCS, castasterone (CS), teasterone and dolicholide], with the last one detected for the first time in cereal species. To some extent freezing tolerance seems to be determined by native hormonal status as control seedlings of tolerant DH lines contained 1.4- and 2.3-fold lower amount of ABA and HCS and 2.3-fold higher amount of SA in comparison to freezing-sensitive ones. Such dependency was not observed in heading plants as significant variation in CS content was the only detected difference. Under stress treatments, tolerant DH lines accumulated significantly lower (75–81%) amount of ABA, which probably reflected lower stress intensity resulting from another defence strategy. In contrast, stress-induced significant almost 2-fold increase in HCS/CS and 2–3-fold decrease in SA content specific for tolerant DH lines of barley suggest the involvement of these molecules in freezing/drought defence. Detected correlations suggest their interaction with nonspecific peroxidase and low molecular weight antioxidants.
Highlights
Hormones are the key factors regulating all aspects of life of any living organism starting from the process of egg cell fertilization and embryo development, up to senescence and death
On the basis of the results received from freezing tolerance test according to the procedure described by Rapacz et al (2011), the doubled haploid (DH) lines of barley used in this experiment were identified as (1) freezing tolerant: DH602 and DH534, (2) moderately tolerant: DH561, DH61, DH435 and DH584 and (3) freezing susceptible: DH65, DH158, DH575 and DH363 (Fig. 1)
The estimation of drought tolerance was performed according to Hura et al (2017) based on leaf water content (LWC) and leaf water loss (LWL) parameters according to the following equations: LWC = ((LFM − LDM)∕LFM) × 100%, LWL = [(LWCC − LWCDT)∕LWCC] × 100%, where LFM is leaf fresh mass, L DM is leaf dry mass after 72-h lyophilization, LWCC is leaf water content of control plants, LWCDT is leaf water content of drought-treated plants
Summary
Hormones are the key factors regulating all aspects of life of any living organism starting from the process of egg cell fertilization and embryo development, up to senescence and death. Apart from their role in development and basic metabolism, another crucial role played by these compounds is the acclimation of living organisms to changing environment (Verma et al 2016; Wani et al 2016). ABA plays several key roles in the regulation of a plant’s life cycle and its environmental response (Hirayama and Shinozaki 2007). It is worth noting that in both cases the mechanisms of biochemical defence against dehydration, characteristic for the action of virtually all stress factors, are activated
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