Global warming is a serious problem, with significant negative impacts on agricultural productivity. To better understand plant anatomical adaptation mechanisms as responses to heat stress, improved basic knowledge is required. This research studied the physiological and anatomical responses of Khao Dawk Mali 105 (KDML105) to artificial heat stress. Dehusked seeds were sterilized and cultured on Murashige and Skoog (MS) medium, supplemented with 3 mg/L 2,4-Dichlorophenoxyacetic acid (2,4-D) for callus induction. The cultures were maintained at 25 °C and 35 °C for 4 weeks, while the other culture was treated with heat shock at 42 °C for 1 week before further incubation at 25 °C for 3 weeks. Results revealed that elevated temperatures (35 °C and 42 °C) adversely impacted seedling growth. Plant height, root length, leaf number per plant, fresh and dry weight, chlorophyll a, chlorophyll b and total chlorophyll content decreased after heat stress treatment, while malondialdehyde (MDA) and electrolyte leakage percentage significantly increased, compared to the control. Heat stress induced ROS accumulation, leading to lipid peroxidation and membrane instability. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) results also confirmed negative correlations between MDA, electrolyte leakage and other parameters. MDA content and electrolyte leakage are effective indicators of heat stress in rice. Surface anatomical responses of rice seedlings to heat stress were studied but significant alterations were not observed, and heat stress had no significant negative effects on KDML105 calli. Size and mass of calli increased because heat stress stimulated gene expression that induced thermotolerance. Our results provide useful information for rice breeding and heat stress tolerance programs to benefit long-term global food security.

Pokeweed, Phytolacca americana L., is considered a widely spreading invasive plant, while saponin contents accumulated in the roots have pharmaceutical uses, such as rheumatism treatments and anti-inflammation. Adventitious root cultures are an important source of diverse secondary metabolites, which have significant applications in various fields. This study focused on the optimization of parameters for root induction using different medium states and treatments with auxins on a pokeweed leaf. Semisolid and liquid MS (Murashige and Skoog, 1962) media were supplemented with indole-3-butyric acid (IBA) and 1-naphthylacetic acid (NAA) at 0.5, 1, 2, and 4mg/L. Root growth parameters, e.g., induction percentage, root numbers, length, and weight, were measured to determine the adventitious root induction efficiency. Total phenolic content, total flavonoid content, total saponin content, and antioxidant activity were recorded. Results showed that adventitious roots induced in semisolid MS medium supplemented with 0.5mg/L NAA exhibited a high density of lateral roots. Appropriate medium state and auxin for adventitious root induction in pokeweed were determined as semisolid medium supplemented with 2mg/L NAA. Considering phytochemicals, adventitious roots induced in liquid medium containing 0.51mg/L NAA had the highest yield extract percentage. Additionally, adventitious roots cultivated in a liquid medium enriched with 1mg/L NAA exhibited the highest phenolic and saponin contents. A principal component analysis (PCA) biplot and hierarchical cluster analysis (HCA) heatmap demonstrated different response patterns between semisolid and liquid media applied with NAA. The results of the semisolid media were grouped together due to high expression levels of the root induction parameters, while elevated phytochemical values were observed in the liquid media treatments. The results suggested two different media that provide the highest adventitious root induction efficiency and the greatest phytochemical contents: semisolid medium with 2mg/L NAA and liquid medium with 1mg/L NAA, respectively. These culture media can be applied to optimize adventitious root culture of pokeweed and in vitro phytochemical production.

Soil salinity is a severe global stressor causing adverse impacts on irrigated land and drastically reducing crop yields, especially in rice, an important economic crop of Thailand. In this study, the impacts of salt stress on the anatomical and physiological features of 28-day-old rice (Oryza sativa L.) ‘Hom Mali Daeng’ were determined. Various NaCl concentrations (0, 50, 100, 150, and 200 mM) were applied every 2 days, with watering for 2 weeks. The results revealed that salinity stress inhibited the growth of rice. Leaf number, root size, fresh weight, and dry weight were significantly reduced. The electrolyte leakage percentage and malondialdehyde (MDA) content increased after treatment with high NaCl concentrations, while the SPAD unit and chlorophyll content were not significantly different between the control and NaCl treatments. Leaf anatomy changes were studied using freehand section and peeling techniques after salinity stress treatment. Lamina thickness in all treatments decreased, while cell wall and cuticle thickness increased. Stomatal density in all treatments significantly increased. Major vascular bundle, vessel, and phloem area of the 100 mM NaCl treatment were different when compared with the control and other treatments. The results provide information about the physiological and anatomical adaptation of ‘Hom Mali Daeng’ rice, which will be useful for further research in this and other rice cultivars.

The pokeweed (Phytolacca americana L.) plant is native to North America and contains bioactive compounds with medicinal potential, particularly phenolics and saponins. This study enhanced the production of secondary metabolites in pokeweed callus cultures using sodium chloride (NaCl) and polyethylene glycol (PEG) as elicitors under aseptic conditions. Pokeweed seeds were cultured on Murashige and Skoog (MS) medium for 8 weeks. Fully expanded leaves from the second to third position from the shoot were excised and induced to form calli on MS medium supplemented with 2 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) for 5 weeks. Fully developed calli were elicited with PEG6000 at concentrations of 0, 1.25, 2.5, and 5% (w/v) in combination with NaCl at concentrations of 0, 100, 200, and 300 mM for 15 days. Callus growth was recorded, followed by drying and extraction using methanol (MeOH) for biochemical analysis. Calli elicited with 2.5% PEG and 300 mM NaCl exhibited the highest total phenolic content (TPC) (21.063 µg GAE/mg DW) and total flavonoid content (TFC) (1.927 µg QUE/mg DW). The highest antioxidant activities determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and ferric ion reducing antioxidant potential (FRAP) assays were 0.998, 1.574, and 0.998 µg TE/mg DW, respectively. The elicitation of pokeweed calli with 300 mM NaCl yielded the highest amount of Esculentoside A (EsA) (15.753 µg/mg DW). All the elicitor treatments significantly enhanced metabolite accumulation compared to the control group (p < 0.05). The findings indicated that elicitation with PEG and NaCl effectively enhanced the production of secondary metabolites in P. americana callus cultures. This study offers a promising alternative approach for utilizing P. americana in pharmaceutical and medicinal applications.