Acta Physiologiae Plantarum

Mkhize, Kwanele Goodman Wandile; Minibayeva, Farida; Beckett, Richard Peter

doi: 10.1007/s11738-022-03458-8pmid: N/A

Lichens often grow in microhabitats where they receive more light than they are capable of using to fix carbon. Unless regulated, this excess energy can end up activating oxygen, thereby forming reactive oxygen species (ROS). These ROS can damage the photosynthetic apparatus and other cellular components, causing photoinhibition and photo-oxidative stress. Tolerance to high light theoretically can be achieved in a variety of ways, but for lichen photobionts, our knowledge of the precise mechanisms involved is rather fragmentary. Here, we show that tolerance to photoinhibition in the cephalolichen Crocodia aurata could be increased by pretreating thalli at a moderate light intensity for 48 h. Increased tolerance was correlated with increased ability to avoid oxidative stress by dissipating the excess energy as heat, here assessed by measuring non-photochemical quenching (NPQ). Increased tolerance only occurred when thalli were pretreated hydrated. The same pretreament did not increase tolerance in the cyanolichen Sticta fuliginosa, which grows in similar habitats to Crocodia, suggesting that cephalo- and cyanobacterial lichens may require different pretreatment conditions. Similarly, tolerance was not increased in collections of the chlorolichen Ramalina celastri from exposed habitats, although additional experiments showed that fluorescence parameters in Ramalina can display considerable plasticity. It seems likely that in “sun” populations tolerance is fully expressed and cannot be further increased. However, the ability to harden Crocodia to photoinhibitory stress could provide a foundation for more detailed investigations into the mechanism of photoprotection in lichen photobionts such as the type of NPQ or the role of antioxidant enzymes.

Silva, Dayane Mércia Ribeiro; Santos, Jania Claudia Camilo dos; Christensen, Nicholas; Silva, Marcelo de Almeida

doi: 10.1007/s11738-022-03454-ypmid: N/A

Water deficit affects safflower development, but its effects can be mitigated by potassium fertilization. We use morphological, nutritional and production components to evaluate the effect of potassium fertilization in safflower response to water deficiency and subsequent rehydration. The experimental design used was completely randomized in a 3 × 3 factorial scheme, consisting of doses (0, 80, 160 kg ha−1) of potassium chloride (KCl) and water tensions in the soil,  – 10 kPa (without water deficiency),  – 50 kPa (moderate water deficiency) and  – 70 kPa (severe water deficiency), with four repetitions. Plant height, number of leaves, number of branches, number of capitula and stem diameter were evaluated at 30 days after the imposition of water regimes and at 20 days after rehydration. The nutritional status of leaves and grains was evaluated after rehydration and at harvest, respectively, through the levels of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg). Potassium fertilization positively influenced morphology, nutrition and safflower production, and the effects were accentuated with the application of 160 kg ha−1 of KCl without water deficiency and under moderate water deficiency. Under severe water deficiency, there was no recovery of safflower. Therefore, the dose of 160 kg ha−1 of KCl is adequate to mitigate the effects of only moderate water deficiency in safflower.

Lyu, Ruiheng; Wang, Rui; Wu, Cuiyun; Bao, Yajing; Guo, Peng

doi: 10.1007/s11738-022-03450-2pmid: N/A

Sour jujube is a tree species native to China, which has often been used as the rootstock for the propagation of other cultivars of jujube. In addition, its fruit can be used in the practice of traditional Chinese medicine. Thus, sour jujube has been regarded as a highly valuable plant scientifically and ecologically. Sour jujube is mostly planted in Northwest China and has extremely high salt tolerance. However, the molecular mechanism of its salt tolerance is yet to be fully understood. This study was carried out in the Laboratory of Agricultural College of Dalian Nationalities University. Two treatments were performed on the leaves of sour jujube seedlings with the experimental group (H3) being treated by 300 mM NaCl for 3 h, and the control group (CK) by sterile water for 3 h. A total of 47.02 GB of valid data and 32,730 annotated genes were obtained. Based on the gene expression in the comparison group, 2295 significantly differentially expressed genes (DEGs) were obtained, of which 807 and 1488 were upregulated and downregulated, respectively. According to gene function annotation and enrichment analysis, 148 genes were obtained, which are mainly involved in signal transduction of plant hormones (38), homeostasis of cell walls (27), secondary metabolism of organic matter (32), and redox reactions (20) in the leaves of sour jujube seedlings under salt stress. Among these DEGs, some stress-related transcription factors (31) were also identified. In addition, under salt stress, raffinose family oligosaccharide (RFO) metabolism in sour jujube seedlings was found to be greatly accelerated. By investigating the molecular responses of jujube seedlings under salt stress, our study provides a scientific basis for jujube cultivation in saline-alkali land, which is beneficial to further improvement of the salt tolerance of grafted jujube trees.

Yadav, Manisha; Gupta, Praveen; Seth, Chandra Shekhar

doi: 10.1007/s11738-022-03445-zpmid: N/A

Solanum lycopersicum L. is a worldwide grown crop with salient economical values for food industries. A pot experiment was conducted to investigate cadmium toxicity in Solanum lycopersicum L. cv Pusa Ruby and its possible amelioration by foliar supplementation of α-lipoic acid (ALA). Plants were grown under different CdCl2 concentrations (10, 25, 50, 100 mg kg−1 soil), and were sprayed twice with 0.1 mM ALA at the 30th and 45th day of plant growth. The Cd accumulation, plant growth, toxicity indices, photosynthetic pigments, nitrogen metabolism, and antioxidant enzymes were determined in 60 days old plants. Results showed that Cd accumulation was considerably higher in roots than shoots. Cadmium toxicity decreased the plant growth, photosynthetic pigments, and nitrogen assimilating enzymes activity, while significantly (P ≤ 0.05) enhanced the lipid peroxidation and H2O2 accumulation in a dose-dependent manner. Foliar supplementation of ALA alleviated Cd toxicity on photosynthetic pigments and nitrogen metabolism by decreasing the Cd accumulation, toxicity indices, and improving the activity of antioxidant enzymes at each respective Cd treatment. The H2O2 and MDA content were decreased by 23% and 55%, respectively, at 10 mg Cd treatment. Under similar conditions, the NR, GOGAT, SOD, and APX activity were enhanced by 10%, 21%, 26%, and 10%, respectively, over the control. The study concludes that ALA can be potentially used in the amelioration of cadmium toxicity in tomato plants.

Alberto, Diana; Ramel, Fanny; Sulmon, Cécile; Gouesbet, Gwenola; Couée, Ivan

doi: 10.1007/s11738-022-03449-9pmid: N/A

Herbicides and their degradation products contribute to soil pollution and to its impact on soil biodiversity and functioning. Soil herbicide pollution presents characteristics of global planetary threats, with harmful consequences for soil ecology, for ecosystem functions and services mediated by natural plant communities and for crop production sustainability. However, the range and the mechanisms of soil herbicide pollution effects on plants are not fully understood. Effects on roots, as a first line of pollutant exposure, and on root plasticity, as a driver of below-ground ecological processes, must be further characterized. Because of worldwide intensive use of atrazine, of persistence in the environment and of toxicological effects, atrazine and its derived metabolites are typical persistent organic pollutants of soils. The coherent chemical series consisting of atrazine, desethylatrazine and hydroxyatrazine was used to analyse potential effects of triazine xenobiotics on root plasticity processes. Responses to atrazine, desethylatrazine and hydroxyatrazine applied at root level were comparatively analyzed in the model plant Arabidopsis thaliana, which is highly responsive to triazine xenobiotics. We report that triazine xenobiotics, whether as herbicidally active compounds or as degradation products, affect root plasticity in terms of primary root growth, lateral root development and root hair development, and that these effects differentially interact with the light, carbon and cytokinin status of the plant. The adaptive significance of these effects and of their interactions is discussed in terms of toxicity of, or resistance to, residual soil contaminants and in terms of potential cascading impact on plant and ecosystem functioning.

Shelyakin, Mikhail; Malyshev, Ruslan; Silina, Ekaterina; Zakhozhiy, Ilya; Golovko, Tamara

doi: 10.1007/s11738-022-03457-9pmid: N/A

Lichens are phototrophic organisms tolerant to adverse environmental conditions. However, the mechanisms underlying their stress tolerance are not fully understood. For photosynthetic organisms depending on solar radiation, UV-B radiation (280–320 nm) acts as a stress factor. We studied the pro-/antioxidant and respiratory metabolism of Peltigera aphthosa to identify adaptive responses of lichen to a physiological dose of UV-B radiation (14 kJ day−1 for 10 days). A browning of the upper cortex, the appearance of dark spots in the medulla layer of treated thalli, and an increase in the browning reflectance index indicated the synthesis of protective UV screening pigments. UV-B treatment did not cause significant changes in the photosynthetic activity of thalli and isolated algal cells. More intense lipid peroxidation activity and transient changes in H2O2 content accompanied the acclimation process. Higher superoxide dismutase and catalase isoenzyme levels and activity were noted 4 days following the termination of the UV-B treatment. Increased alternative respiration capacity (AP) and a contribution of this energy-dissipating respiratory pathway of up to 45% of the total respiration rate were noted in treated thalli, but not in isolated algal cells. These data demonstrate the UV-B effect on the Peltigera aphthosa respiratory metabolism to be higher due to reactions of the mycobiont than those of the photobiont. We suggest that the activation of the energy-dissipating AP in mycobiont mitochondria may be associated with the synthesis of protective pigments.

Ahmed, Lina Qadir; Escobar-Gutiérrez, Abraham J.

doi: 10.1007/s11738-022-03439-xpmid: N/A

Key messageCocksfoot shows intra-specific variability in its response to constant temperature during germination.AbstractTemperature, in conjunction with other environmental factors, controls plant development, including seed germination and its timing, which directly affects seedling survival. Indirectly, seed germination affects recruitment of individuals and hence the genetic dynamics of grasslands communities. Cocksfoot (Dactylis glomerata L.) is a major species growing in temperate and Mediterranean grasslands. Six accessions of D. glomerata, including four natural populations and two commercial varieties were evaluated for their responses to eight constant temperatures, from 5 to 40 ℃, with increases by 5 ℃. Four replicates of one-hundred seeds per accession were put in the dark and counted for germination at variable frequencies and duration that depended on temperature treatments. We estimated maximum germination percentage, maximum germination rate as well as apparent initial time and time when 50% of seed germinate. The F test showed significant difference (P < 0.01) between the response curves of various accessions. At least four types of responses can be distinguished. Temperature for maximum germination ranged from 5 to 25 ℃, depending on accessions. The results of this study reveal the existence of intraspecific genetic variability during germination in D. glomerata for the response to temperature. Such variability could be used to select new varieties adapted to thermal conditions induced by ongoing climate change.

He, Mengdi; Jiang, Yanjie; Liu, Lulu; Zhong, Xuanbo; Zhao, Yun; Ma, Wujun; Tang, Guixiang

doi: 10.1007/s11738-022-03460-0pmid: N/A

Water and nitrogen (N) fertilizer are the two main factors affecting wheat growth and yield. Spring wheat cultivars, Spitfire (drought sensitive) and Drysdale (drought tolerant), were used as materials for studying N metabolism physiological and molecular dynamics under water-deficit treatment at high-N level (180 kg hm−2, i.e., 80 mg kg−1) vs. low-N level (22.5 kg hm−2, i.e., 10 mg kg−1) at heading stage in this experiment. The results showed that the chlorophyll, soluble sugar, soluble protein and free amino acid contents; glutamine synthetase (GS), glutamate synthetase (GOGAT) and phosphoenolpyruvate carboxylase (PEPC) enzyme activities; gene GS1 expression; and grain yield were increased at high-N level compared to low-N level under water-deficient stress at heading stage in both cultivars. Relative expressions of genes GDH, GOGAT and PEPC were down-regulated in Spitfire under water-deficit treatment, but were up-regulated in Drysdale. The indicators of root system architecture, including root surface area, total root volume, root diameter and number of root tips and root branches, were increased at high-N level under water-deficient treatment in both cultivars, whereas total root length decreased. The root–shoot ratio of both cultivars decreased to low-N level under water-deficit treatment. The N transfer rate was significantly increased at high-N level after heading for water-deficit treatment. The grain yields of both cultivars were maintained by the high-N level under water-deficit treatment. Our results suggested a high-N level could alleviate the damage from water deficiency by activating genes/enzymes related to wheat carbon and N metabolism.

Tang, Danfeng; Wei, Fan; Quan, Changqian; Huang, Suhua; Huang, Yuan; Wei, Kunhua; Miao, Jianhua

doi: 10.1007/s11738-022-03453-zpmid: N/A

Mesona chinensis Benth (MCB) is an edible and medicinal plant in southern China and Southeast Asian countries. Mitochondria, semi-autonomous organelles in eukaryotic cells, contain their own genome (mitogenome) and are involved in various cellular processes. Codons are the core elements of protein translation in gene-coding regions. It is of great significance to analyze the characteristics of codon usage in gene-coding regions for gene function and phylogenetic studies. Here, the codon usage pattern and the factors affecting codon usage bias (CUB), and the cluster and phylogenetic analysis based on mitogenomes were determined. Results of nucleotide composition analysis showed an unequal distribution of T, G, A, and C nucleotides and AT bias in MCB mitogenome. The GC, GC1, GC2, GC3 content, codon adaption index (CAI), and effective number codon (ENC) of MCB mitogenome were 43.09%, 48.37%, 42.67%, 38.22%, 0.632, and 55.539, respectively, while those of each gene ranged from 35.61% to 51.85%, 36.25% to 56.69%, 33.46% to 47.76%, 23.08% to 58.15%, 37.81 to 60.02, and 0.564 to 0.680, respectively. 18 out of 28 genes showed the highest GC1 content and the lowest GC3 content, and the general order of GC content in different codon positions was GC1 > GC2 > GC3. Further analysis of the neutrality plot, ENC-plot, and PR2-bias plot revealed that the CUB of MCB mitogenome was affected by natural selection and mutation. Seven optimal codons, TTG, GAC, TCA, AGA, ACC, GGG, and ATA were determined in MCB mitogenome. The phylogenetic tree based on mitogenome sequences and the cluster analysis based on relative synonymous codon usage (RSCU) values indicated that the CUB of mitogenome might have to do with the genetic relationship among species. Overall, the current study positively contributed to the molecular mechanism of biological adaptation and the evolutionary relationship of MCB.

Xu, Liugen; Zhou, Yong; Cheng, Jie; Kang, Liqing; Qiang, Yuqi; Yan, Xuemei; Yan, Yuhua; Tang, Ying; Wang, Yihua; Li, Hua; Song, Jianbo

doi: 10.1007/s11738-022-03459-7pmid: N/A

Thioredoxin (Trx) is a ubiquitous heat-stable protein that acts as an electron donor in many reduction reactions and is expressed in all organisms. In this study, the Trxs were searched from the whole genome of Medicago truncatula. As a result, 46 MtTrx genes were found and grouped into four groups by phylogenetic analysis. Chromosomal location and synteny analyses have suggested that both fragmental and tandem duplication contribute to MtTrx gene expansion. Tissue expression analysis has shown that several MtTrx genes may play vital functions in specific tissues, e.g., MtTrx30, MtTrx33 and MtTrx39. Moreover, the expression profiles of MtTrx genes under stresses revealed that 21, 27, and 29 MtTrxs were regulated by cold, drought and salt, respectively, and 11 of these genes responded to all stresses mentioned above (MtTrx3, 13, 17, 18, 22, 24, 25, 31, 32, 33, and 39). Combined with the results of promoter analysis, multiple MtTrx genes were deduced to participate in abiotic stress responses. Results from this study will inspire the future research on functional analysis of MtTrx genes, especially their roles in response to abiotic stress.