Floodwater Depth Causes Different Physiological Responses During Post-flooding in Willows

Micromorphology and silicon of the leaf epidermis in the psammophyte Alyssum desertorum are sensitive to soil flooding

The ultrastructure of the leaf epidermis and the localization and content of silicon in epidermal cells of the psammophyte Alyssum desertorum Stapf (Brassicaceae) were investigated using electron microscopy and laser confocal microscopy. The study aimed to examine the effect of flooding on the epidermal structure of the leaves, study the presence, localization, and content of silicon in the epidermal cells and determine whether changes in soil moisture affect the silicon content in the leaf epidermis. Silicon inclusions were observed in trichomes and typical epidermal cells on both leaf surfaces, with varying content depending on the cell type, leaf surface, and conditions growth. Soil flooding was found to influence the leaf epidermis ultrastructure and the silicon content in the epidermal cells of A. desertorum. Trichomes and pavement cells were identified as the main accumulators of silicon inclusions and wax-like structures. These findings suggest that changes in leaf microstructure and silicon content contribute to the normal functioning of psammophyte plants and can be considered signs of plant phenotypic plasticity and adaptive markers depending on water supply conditions.

Adaptation of the Invasive Plant Sphagneticola trilobata to Flooding Stress by Hybridization with Native Relatives

Hybridization is common between invasive and native species and may produce more adaptive hybrids. The hybrid (Sphagneticola × guangdongensis) of Sphagneticola trilobata (an invasive species) and S. calendulacea (a native species) was found in South China. In this study, S. trilobata, S. calendulacea, and Sphagneticola × guangdongensis were used as research materials to explore their adaptability to flooding stress. Under flooding stress, the ethylene content and the expression of key enzyme genes related to ethylene synthesis in Sphagneticola × guangdongensis and S. calendulacea were significantly higher than those in S. trilobata. A large number of adventitious roots and aerenchyma were generated in Sphagneticola × guangdongensis and S. calendulacea. The contents of reactive oxygen species and malondialdehyde in Sphagneticola × guangdongensis and S. calendulacea were lower than those in S. trilobata, and the leaves of S. trilobata were the most severely damaged under flooding stress. The results indicate that hybridization catalyzed the tolerance of Sphagneticola × guangdongensis to flooding stress, and the responses of Sphagneticola × guangdongensis to flooding stress were more similar to that of its native parent. This suggests that hybridization with native relatives is an important way for invasive species to overcome environmental pressure and achieve invasion.

Comparative transcriptomic analysis reveals potential mechanisms for high tolerance to submergence in arbor willows

BACKGROUND

Submergence threatens plant growth and survival by decreasing or eliminating oxygen supply. Uncovering the complex regulatory network underlying the tolerance of Salix to submergence and identifying the key regulators are important for molecular-assisted breeding of Salix.

METHODS

In this study, we screened germplasm resources of arbor willows and discovered both submergence-tolerant and submergence-sensitive varieties. Then, by performing RNA-seq, we compared the differences between the transcriptomes of two varieties, i.e., the submergence-tolerant variety "Suliu 795" and the submergence-sensitive variety "Yanliu No. 1," and the different submergence treatment time points to identify the potential mechanisms of submergence in Salix and the unique approaches by which the variety "Suliu 795" possessed a higher tolerance compared to "Yanliu No. 1".

RESULTS

A total of 22,790 differentially expressed genes were identified from 25 comparisons. Using gene ontology annotation and pathway enrichment analysis, the expression pattern of transcriptional factors, important players in hormone signaling, carbohydrate metabolism, and the anaerobic respiration pathway were found to differ significantly between the two varieties. The principal component analysis and qRT-PCR results verified the reliability of the RNA sequencing data. The results of further analysis indicated that "Suliu 795" had higher submergence tolerant activity than "Yanliu No. 1" because of three characteristics: (1) high sensitivity to the probable low oxygen stress and initiation of appropriate responding mechanisms in advance; (2) maintenance of energy homeostasis to prevent energy depletion under hypoxic stress; and (3) keep "quiescence" through fine-tuning the equilibrium between phytohormones GA, SA and ethylene.

Modeling of the Potential Geographical Distribution of Three Fritillaria Species Under Climate Change

Fritillaria species, a well-known Chinese traditional medicine for more than 2,000 years, have become rare resources due to excessive harvesting. In order to balance the economical requirement and ecological protection of Fritillaria species, it is necessary to determine (1) the important environmental variables that were responsible for the spatial distribution, (2) distribution change in response to climate change in the future, (3) ecological niche overlap between various Fritillaria species, and (4) the correlation between spatial distribution and phylogenies as well. In this study, the areas with potential ecological suitability for Fritillaria cirrhosa, Fritillaria unibracteata, and Fritillaria przewalskii were predicted using MaxEnt based on the current occurrence records and bioclimatic variables. The result indicated that precipitation and elevation were the most important environmental variables for the three species. Moreover, the current suitable habitats of F. cirrhosa, F. unibracteata, and F. przewalskii encompassed 681,951, 481,607, and 349,199 km2, respectively. Under the scenario of the highest concentration of greenhouse gas emission (SSP585), the whole suitable habitats of F. cirrhosa and F. przewalskii reach the maximum from 2021 to 2100, while those of F. unibracteata reach the maximum from 2021 to 2100 under the scenario of moderate emission (SSP370) from 2021 to 2100. The MaxEnt data were also used to predict the ecological niche overlap, and thus high overlap occurring among three Fritillaria species was observed. The niche overlap of three Fritillaria species was related to the phylogenetic analysis despite the non-significance (P > 0.05), indicating that spatial distribution was one of the factors that contributed to the speciation diversification. Additionally, we predicted species-specific habitats to decrease habitat competition. Overall, the information obtained in this study provided new insight into the potential distribution and ecological niche of three species for the conservation and management in the future.