Recently, grafting has been used to improve abiotic stress resistance in crops. Here, using watermelon ‘Zaojia 8424’ (Citrullus lanatus) as scions, three different gourds (Lagenaria siceraria, 0526, 2505, and 1226) as rootstocks, and non-grafted plants as controls (different plants were abbreviated as 0526, 2505, 1226, and 8424), the effect of cold stress on various physiological and molecular parameters was investigated. The results demonstrate that the improved cold tolerance of gourd-grafted watermelon was associated with higher chlorophyll and proline content, and lower malondialdehyde (MDA) content, compared to 8424 under cold stress. Furthermore, grafted watermelons accumulated fewer reactive oxygen species (ROS), accompanied by enhanced antioxidant activity and a higher expression of enzymes related to the Calvin cycle. In conclusion, watermelons with 2505 and 0526 rootstocks were more resilient compared to 1226 and 8424. These results confirm that using tolerant rootstocks may be an efficient adaptation strategy for improving abiotic stress tolerance in watermelon.

Plant respiratory burst oxidase homologs (rbohs), a source of reactive oxygen species (ROS), play a central role in the response to biotic and abiotic stresses in plants. Here, an rboh gene from the seaweed Gracilariopsis lemaneiformis (Glrboh) was characterized and analyzed in terms of its structure and changes in its expression profile in response to high salinity, high temperature and phytohormone treatments. The results show that high salinity and high temperature mostly induced Glrboh expression at the mRNA, protein and enzyme activity levels within 3–6 h, and the levels decreased thereafter, but there was an almost continuous decline in Glrboh mRNA during the 24 h following exposure to high temperature. Under heat stress, abscisic acid (ABA) dramatically enhanced the levels of Glrboh mRNA at 3 h and increased Glrboh protein expression and enzyme activity throughout most of the 24-h period. However, salicylic acid (SA) and methyl jasmonate (MJ) had only slight and varied effects on Glrboh expression. These results indicate that Glrboh is involved in heat and salt stress responses and that the phytohormone ABA is more closely related to ROS production in this alga than SA and MJ.

Salvia changchuniana (Lamiaceae), a new species from Zhejiang Province of eastern China, is described with illustrations. The new species is similar to Salvia liguliloba, but differs in having wider leaves, basal leaf blade ovate-elliptic, ovate-oblong or broadly ovate, 7‒13 cm long, 4‒9 cm wide, cauline leaf blade ovate-elliptic, ovate or broadly ovate, 9.5‒13(‒20) cm long, 4.5‒7(‒12) cm wide, inflorescence rachis densely recurved pubescent and glandular, calyx glandular externally, with ribs short-hispidulous, corolla short, 1.3‒1.5 cm long, tube pubescent externally, limb villous and glandular externally, middle lobe of lower lip compressed rounded-spathulate, ca. 3 mm long, ca. 2.5 mm wide, margin praemorse. All species of Salvia ser. Ligulilobae were compared with the new species.

Members of the heat shock protein 20 (HSP20) family of proteins play an important role in responding to various forms of stress. Here, the expression of ClaHSP17.4 was induced by heat stress in watermelon. Then, a floral dipping approach was used to introduce the pCAMBIA1391b-GFP overexpression vector encoding the heat tolerance-related gene ClaHSP17.4 from watermelon into Arabidopsis thaliana, and we obtained ClaHSP17.4-overexpressing Arabidopsis plants. Under normal conditions, the phenotypes of transgenic and wild-type (WT) Arabidopsis plants were largely similar. Following exposure to heat stress, however, the germination rates (96%) of transgenic Arabidopsis plants at the germination stages were significantly higher than those of wild-type idopsis (17%). Specifically, the malondialdehyde (MDA) content of transgenic Arabidopsis was half that of the control group, while the activities of peroxidase (POD) and superoxide dismutase (SOD) were 1.25 times those of the control group after exposure to high temperatures for 12 h at the seedling stages. The proline content in ClaHSP17.4-overexpressing transgenic Arabidopsis increased by 17% compared to WT plants (* p < 0.05), while the soluble sugar content rose by 37% (* p < 0.05). These results suggest that ClaHSP17.4 overexpression indirectly improves the antioxidant capacity and osmotic regulatory capacity of Arabidopsis seedlings, leading to improved survival and greater heat tolerance. Meanwhile, the results of this study provide a reference for further research on the function of the ClHSP17.4 gene and lay a foundation for breeding heat-tolerant watermelon varieties and advancing our understanding of plant adaptation to environmental stress.