Plants

Drought stress significantly limits crop yield by disturbing plant water status and redox homeostasis, leading to oxidative stress and growth suppression. Anthocyanins, with their strong antioxidant properties, are closely linked to abiotic stress adaptation. The R2R3-MYB transcription factor SlANT1 promotes anthocyanin biosynthesis in tomato, yet its role in drought resistance remains poorly understood. This study explored the function of SlANT1 in tomato under drought conditions. SlANT1 expression was upregulated under both drought and high salinity. The overexpression of SlANT1 resulted in higher anthocyanin accumulation and reduced leaf and stem dimensions. Under drought, SlANT1-overexpression (SlANT1-OE) plants maintained a greater leaf relative water content, showed less negative water potential, wilted less, and recovered faster after rewatering. These plants also accumulated lower levels of reactive oxygen species (ROS) and malondialdehyde (MDA). While antioxidant enzyme activities were generally reduced, anthocyanin-dependent ROS scavenging was significantly enhanced. SlANT1 overexpression also modulated carbohydrate metabolism and aquaporin gene expression, elevating sucrose, fructose, glucose, and soluble protein while decreasing starch, thereby supporting osmotic adjustment. Notably, while stomata remained partially open in SlANT1-OE plants during drought, they exhibited reduced stomatal density, which likely compensated for the wider apertures and helped maintain favorable water status, while still sustaining higher photosynthetic rates and photosystem II integrity. These findings demonstrate that SlANT1 enhances drought tolerance through coordinated mechanisms involving anthocyanin-mediated antioxidant protection, improved water relations, and the reprogramming of carbohydrate and aquaporin pathways. SlANT1 thus represents a promising target for breeding drought-resilient, high-anthocyanin tomato varieties.

Background: Paeonia lactiflora Pall. produces substantial quantities of nectar during the bud stage. In the production of cut flowers, this nectar attracts contaminants that compromise the quality of the flowers. The current practice of rinsing flowers with clean water escalates production costs. Consequently, reducing nectar secretion during the bud stage has emerged as a significant technical challenge for the industry. Nonetheless, insufficient fundamental knowledge concerning the structure of P. lactiflora nectaries and the physiology of nectar secretion impedes the development of pertinent regulatory technologies. Methods: This study established a “nectar secretion index” to evaluate nectar production in various P. lactiflora cultivars. Nectar sugar concentration and composition were measured using a refractometer and gas chromatography–mass spectrometry (GC-MS). Observations of changes in nectary epidermal morphology and anatomical structure during nectar secretion were conducted using scanning electron microscopy and light microscopy. Key Results: The quantity of nectar secreted by various P. lactiflora cultivars can differ. The indices were not significantly correlated with flowering period, flower color, or flower type. At the peak of nectar secretion, the sugar concentration of nectar secretion by different cultivars’ flower buds varied. Sucrose is the primary sugar component in this nectar. Nectar is secreted along the basal margins of the bracts and sepals on the abaxial surface of all cultivars. Specialized raised stomata are located on the upper epidermis, through which nectar is secreted. In contrast, the epidermal stomata located outside nectar-secreting areas exhibit a normal morphology. Specialized stomata do not secrete nectar concurrently. The stomatal aperture and the percentage of nectar-secreting stomata at the secretion sites are significantly higher in high-nectar-producing cultivars than in low-nectar-producing cultivars. Anatomical observations of bract nectaries indicate that, irrespective of nectar production levels, specialized stomata are consistently located adjacent to vascular bundles. During the initial stage of nectar secretion, no starch was detected in the bract nectaries. In contrast, the stomata in non-secretory epidermal cells of bracts maintain a normal morphology, and calcium oxalate crystals were observed within the subepidermal tissues. Throughout the nectar secretion process, the content of photosynthetic pigments and the Fv/Fm ratio in the bracts and sepals of various cultivars correlated with nectar secretion volume. Conclusions: This study, informed by observations of numerous P. lactiflora cultivars, elucidates the structural characteristics of its nectaries and the nectar secretion properties of various cultivars during the bud stage. It confirms that these nectaries are classified as extrafloral nectaries, specifically structural nectaries consisting of specialized raised stomata and closely associated vascular bundles beneath them. No significant differences in nectary structure or location were noted among cultivars with differing nectar yields. However, both the aperture of nectary stomata and the percentage of nectar-secreting stomata exhibited a significant positive correlation with secretion levels. The intrinsic photosynthetic potential at the nectary sites varies significantly among cultivars. The nectar is not derived from stored cellular starch but likely originates simultaneously from both photosynthesis and phloem transport. These findings provide a theoretical foundation for the development of subsequent regulatory technologies.

Sunflower (Helianthus annuus L.) is a crop with ornamental and energetic potential, but its propagation is challenged by abiotic stresses such as salinity and water deficit. Ensuring high-quality propagation materials is crucial for healthy plant development. Nanotechnology offers innovative tools to enhance seed performance, stress tolerance, and production efficiency. Among these, carbon nanotubes, a strong, conductive, and thermally resistant material, have shown promise in improving seed quality. This study aimed to evaluate the effects of nanopriming with multi-walled carbon nanotubes (MWCNTs) on the physiological and biochemical performance of sunflower seeds under accelerated aging and stress conditions. Seeds were treated with 100, 200, or 400 mg·L⁻¹ MWCNTs, and parameters such as germination percentage, seedling growth, pigment profile, and oxidative stress indicators were analyzed. The 200 mg·L⁻¹ concentration enhanced germination, root and shoot development, and antioxidant enzyme modulation, while the 400 mg·L⁻¹ dose increased reactive oxygen species, indicating toxicity. Under saline and drought-like conditions, nanopriming with 100–200 mg·L⁻¹ mitigated oxidative damage more effectively than hydropriming. MWCNTs also influenced pigment synthesis, affecting chlorophyll and carotenoid levels. These findings support the potential of carbon nanotube-based nanopriming to improve seed vigor and stress tolerance in sunflower cultivation, though further environmental safety assessments are required.