Acta Physiologiae Plantarum最新文献

Aspalathus linearis (Burm.f.) R.Dahlgren, or rooibos, is an important commercial crop in the Western Cape, South Africa. The growth rate of rooibos is highest during the hot, dry summers typical for this region. This suggests that the plants have a wide range of adaptive responses including morphological, physiological, molecular, and biochemical mechanisms that help them cope with drought and heat stress. This study investigates differential expression of proteins in leaf samples harvested in summer from rooibos plants at two relatively cool, and two relatively hot sites in the Cederberg region. A total of 180 proteins were differentially expressed and of these, 113 proteins were more abundant at cooler sites while 67 proteins were more abundant at the heat-stressed (HS) sites. The higher temperatures at the HS sites led to a reduced protein abundance due to temperature thresholds for protein production during HS. Heat shock proteins were more abundant in the HS plants indicating an enhanced thermotolerance. Plants at the cooler sites overexpressed proteins associated with aiding photosynthesis and protecting photosystems, resulting in better photosynthetic rates and biomass accumulation. High light and moderate HS conditions prompted the regulation of proteins involved in chlorophyll synthesis and light protection to maintain effective functioning. Proteins involved in oxidative stress responses were expressed in plants at all sites, which was mirrored by high concentrations of antioxidants. Rooibos thermotolerance relies on the expression of HSPs and oxidative stress response proteins, while photosynthesis-related proteins dominate the cooler sites, optimizing their function and ultimately growth.

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The incorporation of optimal concentration of polyethylene glycol with the optimized growth regulators in the nutrient medium promoted shoot growth and improved foliar micro-morpho-anatomical traits of Hedyotis biflora which improved the survival success of the plantlets during ex vitro hardening and field trials.

Polyethylene glycol (PEG) is widely recognized as an effective agent for stimulating osmotic stress in plant tissue cultures. In this study, the micropropagated shoots of Hedyotis biflora (L.) Lam was subjected to varied concentrations of polyethylene glycol (PEG-6000) under in vitro conditions to evaluate the effect of PEG on the morpho-anatomical development of shoots. The cultures were established by culturing nodal shoots on Murashige and Skoog (MS) medium supplemented with 2.0 mg L⁻¹ 6-benzylaminopurine (BAP), and the shoots were proliferated on the optimized plant growth regulators (1.0 mg L⁻¹ BAP + 0.5 mg L⁻¹ Kinetin (Kn) + 0.1 mg L⁻¹ Indole-3-acetic acid (IAA). Among the varied concentrations of PEG used in the MS medium, 60 mg L⁻¹ PEG with optimized growth regulators in the medium increased the rate of proliferation and elongation of shoots (14.0 shoots with 7.0 cm length) and leaf area (1.6 cm length × 1.0 cm width) than the control (medium without PEG). The foliar micro-morpho-anatomical elucidations revealed that the control leaves showed a thin cuticle, non-functional stomata, mesophyll with isobilateral tissues, and poorly developed mechanical, dermal, and vascular tissues. The incorporation of 60 mg L⁻¹ PEG (optimal) in the medium increased cuticle thickness, palisade and spongy mesophyll differentiation, functional stomata, dense vascular tissues, and well-developed ground tissues. The PEG-treated shoots showed better rhizogenesis on half-strength MS medium containing 2.0 mg L⁻¹ Indole-3-butyric acid (IBA) (21.0 roots with 4.0 cm average length). These morphometric and structural improvements were sequentially reflected in the increased survival of plantlets (96%) during acclimatization and field transplantation of H. biflora.

Fonio millet is an orphan crop with great potential for economic and food security. However, drought negatively affects its production and yield in semi-arid and arid regions. This study compared the growth and metabolomic profiles of two contrasting fonio cultivars (NGB02089 and NGB02082) in response to water stress at the seedling stage. The results showed variation in the morph-agronomic characters of the cultivars. There were also significant (p < 0.05) positive correlations in the traits studied, which means that the traits can be improved simultaneously. Chlorophyll content increased progressively with weeks after sowing (WAS) but decreased when seedlings were exposed to water stress. The biomass yield of NGB02082 was higher than that of NGB02089, although the latter grew more vigorously. However, NGB02089 had longer roots. The GC–MS analysis identified 12 significant metabolites that differed in composition between the fonio cultivars, including sugars, fatty acids and siloxanes. The amount of siloxane decreased in NGB02082 with increasing drought duration, but increased in NGB02089. Similarly, cis-13-octadecenoic acid was present in NGB02082 at 4 WAS but absent at 5 WAS, while NGB02089 produced more metabolites. Similarly, phthalimide, triacontane, vaccenic acids, and cholestane were produced in response to drought stress duration. The results of this study showed that NGB02089 and NGB02082 have different metabolomic responses to drought, conferring resistance to NGB02089 while NGB0282 is susceptible to drought. The result of this study suggests that metabolic responses to drought may be useful in developing varieties with better tolerance or adaptation to drought conditions.

Further research related to the role of plant-associated bacteria at the molecular level, gene regulation, modulation, and function can lead to hope for enhancing the growth and performance of agricultural plants in harsh environment. Two studies were performed to investigate the function of Azospirillum brasilense in the regulation of proline-responsive gene expression, as well as some important physiological and biochemical traits related to drought resistance in wheat. Wheat seedlings grown from inoculated and uninoculated seeds were grown under no-water-limitation condition for 21 days and then were subjected to two water regimes: 80% of soil water-holding capacity (WHC) and 25% of WHC. The relationship between A. brasilense inoculation and proline accumulation caused by delta-1-pyrroline-5-carboxylate synthase (P5CS) as well as antioxidant system defense was elucidated 2 weeks after water-deficit imposition. Experiment 2 was conducted under greenhouse condition to assess the modulation of photosynthetic traits, cell membrane stability, and relative water content of leaves as well as grain yield in repose to A. brasilense inoculation. Treatments performed in the two experiments were the same, except water-deficit condition in experiment 2 was imposed at anthesis stage. Under water-deficit conditions, inoculation led to lower accumulation rate (82%) of P5CS mRNA as compared to control plants. Under water-deficit condition, inoculated plants showed lower (13.8%) content of proline compared to control plants. Inoculation alleviated the negative effect of water deficiency by increasing the antioxidant enzyme activity as it increased the activity of peroxidase by 11.7%, glutathione peroxidase by 7.3%, catalase by 65% and glutathione reductase by 70% as compared to uninoculated plants. Under water deficiency, plants inoculated with A. brasilense maintained higher photosynthetic parameters such as net carbon dioxide assimilation rate (84%), stomatal conductance (182%), and sub-stomatal carbon dioxide concentration (69%) compared to uninoculated plants. The present study confirmed that expression of the evaluated gene (P5CS) along with the accumulation of proline was a common response of wheat to water deficiency. Both experiments conducted confirmed that. The inoculated plant displayed a lower level of the evaluated gene and proline content, which can be considered for future research and could open a new hope for improving crop resistance to water-deficit stress.

Oat (Avena sativa L.) is prone to stem lodging under field conditions that negatively affect productivity. The present study aimed to determine the association between lodging resistance with culm morphological, anatomical and biochemical traits. The experiment was laid out in randomized block design in Rabi season of 2020–21 and 2021–22 using eight recently released oat genotypes (OL-1769-1, RO-11-1, OL-13, OL-1896, JHO-822, OL-15, OL-14 and OL-12) to evaluate the impact of stem lodging on oat genotypes. Dendrogram analysis depicted that Cluster I genotypes (OL-1769-1, RO-11-1, OL-13) proved to be more efficient in overcoming lodging stress as compared to Cluster III (OL-15, OL-14, OL-12) and Cluster II (OL-1896, JHO-822) genotypes. Cluster I had lower lodging scores plus lower percent reduction in thousand grain weight, lignin content, dry matter yield of lodged plants and higher breaking strength (BS), culm lodging resistance index (CLRI) than Cluster III. Increased lodging also had a negative impact on biomass partitioning. The correlation analysis depicted a negative association of CLRI with second internode length (− 0.841**) while significant positive correlation with second internode diameter (0.808*) and BS (0.949**). Water-soluble carbohydrates (WSC) and starch content varied significantly with lodging. Increased vascular bundle area and xylem tissue contributed towards lodging resistance. This study provides the direct estimation of the differential behavior of oat genotypes towards stem lodging and its effect on morpho-anatomical and biochemical characters. Genotype RO-11-1 showed resistant behavior while OL-15 showed susceptible behavior towards lodging. Our findings demonstrate the potential of using commercially viable genotypes to achieve high and stable yield under field conditions and to identify lodging tolerant genotypes to support future breeding programs.

Codon usage bias (CUB) reflects the unique characteristics of different species and can be used to analyze their evolutionary relationship, enhance the expression efficiency of target genes in heterologous systems, and further offer theoretical insights for research in molecular biology and genetic breeding. The primary objective of this study is to examine the chloroplast gene CUB in 20 Zanthoxylum species, alongside 12 species from other genera within the Rutaceae family, to offer insights for future studies on their chloroplast genomes. In Zanthoxylum plants, the chloroplast gene codons show a preference for terminating with an A/T instead of a G/C base. In the representative chloroplast genome of Zanthoxylum bungeanum, it was discovered that TTT codons are predominantly used for amino acid Phe, while TAT codons are more commonly utilized for amino acid Tyr. Moreover, natural selection strongly influenced the CUB of the chloroplast genomes in Zanthoxylum plants. Based on RSCU values, the optimal codons for these species were identified, with their similarities being highlighted. The phylogenetic tree of Zanthoxylum species was constructed and contrasted with the results of clustering analysis both based on coding sequences, supporting that Zanthoxylum and Toddalia should be considered to be merged. The Subgen. Zanthoxylum represents a substantial branch that has diverged from the Subgen. Fagara and there are significant differences in CUB between these two subgenera. Furthermore, derived from hierarchical clustering analysis utilizing RSCU values, Nicotiana sylvestris was proposed as the compatible heterologous expression receptor for the chloroplast genes of the Zanthoxylum species.

As the king of vitamin C, kiwifruit has high nutritional and economic value. However, with the expansion of its planting area and the application of a large amount of farm manure represented by large livestock manure, kiwifruit is at increasing risk of salt stress, so it is urgent to select salt-tolerant strains of kiwifruit. MYB transcription factors (TFs) play a vital role in responding to abiotic stress and regulating the synthesis of secondary metabolites. There are relatively few reports on the specific gene functions of MYB TFs. In this study, based on the kiwifruit genome database and transcriptome sequencing data, we used bioinformatics to analyze the structure, evolution, and expression patterns of kiwifruit MYB TFs. The results showed that 226 AcMYB TFs were identified, and the phylogenetic analysis classified them into 32 subfamilies. Analysis of the gene structure and conserved motifs revealed that the exon and intron structures of AcMYB in the same subfamily are relatively identical, with only minor differences. In addition, we predicted cis-acting elements associated with hormones, light responses, etc., at the 2000 bp upstream position of the promoter of the AcMYB TFs. Expression profiling based on transcriptome data showed a total of 24 differentially significant genes, of which 11 genes were upregulated, and 13 genes were downregulated. AcMYB100, AcMYB186, AcMYB81, and so on upregulated genes by positively regulating salt stress to minimize the effects caused to the plants, AcMYB145, AcMYB88, AcMYB1, and so on downregulated genes reduced the salt stress effects on plants by negatively regulating salt stress. It suggests that these MYB TFs can modify the effects of salt on kiwifruit. We also identified the signaling pathway of stress regulating MYB TFs in response to salt stress in kiwifruit plants. These results provide a basis for understanding the biological functions and characteristics of the MYB TF family and lay a foundation for further research on salt tolerance breeding in kiwifruit.

The basis for heat tolerance of rice results from complex physiological mechanisms that vary among different varieties. To identify the relationships between growth performance and physiological characteristics of rice under heat stress, 29 rice genotypes at the seedling stage were evaluated for their heat (45 °C) tolerance for 5 days. Increasing proline content was most strongly significantly correlated with malondialdehyde (MDA) content. Proline, MDA and total chlorophyll contents were included in a multivariate analysis to classify the rice genotypes into four heat tolerance groups: tolerant (T), moderately tolerant (MT), sensitive (S), and highly sensitive (HS). The means of the proline content, MDA content, visual symptom score, and upper epidermal layer thickness (UET) were significantly different among the four tolerance groups and tended to increase and then decrease with decreasing levels of tolerance. Together, these findings indicated that these parameters were the most reliable indices for identifying heat tolerance. In addition to the commonly used visual symptom score and growth performance, proline content and UET could be two other useful and less expensive physiological and anatomical index measurements to differentiate heat-tolerant rice from heat-sensitive rice. The results of this study also showed that several local Thai cultivars have high heat tolerance and could be used for obtaining heat tolerance alleles for breeding programs.

Chloris flagellifera (Nees) P. M. Peterson is a species thriving in salt-affected regions across Punjab, Pakistan. To investigate intraspecific variations, six distinct populations were selected from diverse saline environments: (1) Pakka Anna and Sahian Wala from the least saline regions, (2) Jhalar and Kalar Kahar Lake from moderately saline areas, and (3) Uchali Lake and Khabbeki Lake from hyper-saline zones. These populations, originating from a range of salinity gradients, provide a unique opportunity to study the adaptive mechanisms of C. flagellifera to varying levels of soil salinity. Stomata from highly saline areas were small and narrowly elliptical, while they were larger and rhomboidal in moderately saline areas and circular in least saline areas. Populations from hyper-saline environments (Uchali Lake, Khabbeki Lake) displayed remarkable trait variation, including thicker epidermal layers, larger vascular bundles, and efficient osmotic adjustments, indicating their superior salt tolerance. Populations from least saline areas (Sahian Wala, Pakka Anna) showed structural features like thicker leaves and larger epidermal cells that enhance water retention. Moderately saline populations (Kallar Kahar Lake, Jhallar Lake) exhibited intermediate traits, balancing salt tolerance with efficient resource allocation. These anatomical and physiological responses suggest that C. flagellifera exhibits high adaptability to varying salinity stress. The study highlights the potential of hyper-saline populations for use in the reclamation of salt-affected soils, offering a sustainable approach to land restoration.

Vapour pressure deficit (VPD) and blue light (BL) are import signals for stomatal regulation and highly relevant during cultivation of economically important crops such as cucumber in controlled environments. However, the information about combined effects of VPD and BL and the regulation of abscisic acid (ABA) in this respect, is limited and seems to vary between species. This study investigated how moderate (1.12 kPa) or low (0.28 kPa) VPD combined with 5% or 30% BL affect the foliar ABA metabolism, transpiration rate, nutrient uptake, and growth in well-watered cucumber plants (Cucumis sativus ‘Quatro’). Additional BL, regardless of VPD, resulted in a decrease in the nighttime ABA content (52%), as well as increased adaxial stomatal density (8–19%), transpiration rate during the day (40–50%) and foliar nitrogen content (30%). ABA regulation was unaffected by VPD, but the BL levels during the day influenced the ABA inactivation at night; both the transpiration rate and the ABA-glucose ester (ABA-GE) content then increased in 30% BL compared to 5% BL. An increase in starch degradation due to additional BL led to higher content of the transport carbohydrate raffinose in source leaves and increased the fruit appearance rate (fruit day⁻¹) in low VPD but reduced it in moderate VPD. This study provides novel insight into the regulation of ABA under different VPDs and BL proportions in cucumber, and reveals that under well-watered conditions, BL is a stronger determinant of stomatal aperture regulation than ABA. Also, a combination of high VPD and high BL can act as a weak stressor and affect cucumber growth and yield.