Salix viminalis L., a dioecious species, is widely distributed in riparian zones, and flooding is one of the most common abiotic stresses that this species suffers. In this study, we investigated the morphological, anatomical, and physiological responses of male vs. female plants of S. viminalis to flooding. The results showed that the plant height and root collar diameter were stimulated by flooding treatment, which corresponded with higher dry weight of the stem and leaf. However, the dry weight of the underground part decreased, which might be due to the primary root having stopped growing. The little-influenced net photosynthesis rate (P_n) under flooding treatment could guarantee rapid growth of the aboveground part, while the unaffected leaf anatomical structure and photosynthetic pigment contents could ensure the normal operation of photosynthetic apparatus. Under a flooding environment, the production ratio of superoxide free radical (O₂^∙-) and malondialdehyde (MDA) contents increased, indicating that the cell membrane was damaged and oxidative stress was induced. At the same time, the antioxidant enzyme system, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and osmotic adjustment substances, involving proline (Pro) and solute protein (SP), began to play a positive role in resisting flooding stress. Different from our expectation, the male and female plants of S. viminalis performed similarly under flooding, and no significant differences were discovered. The results indicate that both male and female plants of S. viminalis are tolerant to flooding. Thus, both male and female plants of S. viminalis could be planted in frequent flooding zones.

The compatibility of mycorrhizal fungi with the early growth stage of orchids is essential for their growth. In this study, the compatibility and promotion effects of 14 Tulasnella strains from different hosts were studied by co-culturing them with the protocorms of Dendrobium crepidatum, which has high ornamental and economic value in China. The ITS–LSU–SSU–TEF combined sequence analysis divided the 14 strains into three clades belonging to Tulasnella calospora (clades A and B) and Tulasnella asymmetrica (clade C). All the strains were compatible with D. crepidatum protocorms within 90 d of the co-culture. Strain T12 in Clade A had a significantly higher (p < 0.05) effect on the biomass and morphology of D. crepidatum, and strain T13 in Clade C had a significantly lower (p < 0.05) effect than the other strains. Through morphological principal component analysis, we constructed a hierarchical cluster analysis tree, which was consistent with the phylogenetic tree of these 14 strains at the clade level. Orthogonal partial least squares-discriminant analysis showed that these strains have an important effect on the plant height, root number, and length of D. crepidatum. The findings of this study will contribute to the identification of Tulasnella strains, conservation of D. crepidatum resources, and commercial utilization of mycorrhizal technology.

Dendrobium jizhuyeense, a new species from Sichuan, China, is described and illustrated in this study. Morphological study indicates that D. jizhuyeense is similar to D. hancockii, but differs in having oblong sepals, obovate-elliptic petals and an obovate lip, including a smaller stem, smaller leaf and different flower type. Molecular analyses based on nuclear and plastid markers indicate that D. jizhuyeense is closely related to D. hancockii, belonging to section Holochrysa.

Dendrobium nobile is a prized orchid species with both medicinal and ornamental values, known for accumulating flavonoids that contribute to its bioactivity and flower pigmentation. Chalcone isomerase ( CHI ), a key enzyme in the flavonoid biosynthetic pathway, catalyzes the conversion of chalcone to naringenin, thereby promoting the production of anthocyanins and other flavonoids. In this study, we present the first systematic analysis of the CHI gene family in D. nobile , classifying them into two subfamilies. Expression profiling revealed that DnCHI1 , a type IV CHI , is highly expressed in petals, suggesting a potential role in anthocyanin metabolism. Heterologous transient overexpression assays showed that DnMYB90 significantly downregulated endogenous PeCHI expression and reduced anthocyanin accumulation, whereas DnCHI1 overexpression resulted in a 15-fold increase in anthocyanin content. Dual-luciferase reporter and yeast one-hybrid assays further confirmed that DnMYB90 acts as a transcriptional repressor of DnCHI1 . These results provide new insights into the regulatory module in anthocyanin biosynthesis in D. nobile , highlighting the functional divergence of CHI genes and their interaction with MYB transcription factors.