No abstract

[Objective] To investigate the salt resistance growth status and photosynthetic characteristics of Prunus mume and saline-alkaline resistance of different Prunus mume varieties against mixed salt stress, aiming to provide scientific basis for the application of Prunus mume in saline-alkali land. [Methods]. Taking the Prunus mume 'ZaohuaLve' and Prunus mume 'Meiren' under two years of cutting seedlings as examples, NaCl and NaHCO3 were prepared into treatment solution at a molar mass ratio of 1:1, with six gradients (i.e., 0 (CK), 100 (S1), 200 (S2), 300 (S3), 400 (S4) and 500 (S5) mmol L-1) to observe the growth status and photosynthetic reaction of test plants under different salt concentrations. [Results] With the increase of salt treatment concentration and stress time, the growth amount of leaf length, leaf width and ground diameter of the two kinds of Prunus mume decreased, and the Prunus mume 'ZaohuaLve' salt tolerance threshold (330.189 mmol L-1) is greater than Prunus mume 'Meiren' (292.453 mmol L-1). On the other hand,  the chlorophyll content of the two Prunus mume increased first and then decreased, and the maximum, actual quantum yield of PS Ⅱ and photochemical quenching coefficient decreased as a whole. The net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of the two Prunus mumes decreased overall. For the Prunus mume 'ZaohuaLve', Ci values increased at 0 - 10d, and the changes were inconsistent in Pn, Gs and Ci at later stages of salt stress. The overall trends in the Pn, Ci, and Gs values of Prunus mume 'Meiren' were consistent for the 100 and 200mmol L-1 treatments. [Conclusion] The growth index and photosynthetic index of the two Prunus mumes in the early stage of salt stress are not obvious with salt tolerance. The Prunus mume 'Meiren' salt stress was dominated by stomatal restriction in the early stage, while non-stomatal restriction was the main factor affecting photosynthesis in the later stage. By contrast, the two factors may coexist simultaneously in the Prunus mume 'Meiren'. Overall, the Prunus mume 'ZaohuaLve' was stronger than Prunus mume 'Meiren' regarding the saline-alkaline resistance.

Herbaceous peony (Paeonia lactiflora Pall.) is an ancient ornamental crop and, in recent decades, an emerging popular cut flower. Straight stems are a vital criterion for cut herbaceous peony selection, while many cultivars bend as the plant develops. Pectin helps maintain the mechanical strength of the cell wall. However, little is known about its role in the stem bending of herbaceous peony. Two herbaceous peony cultivars with contrasting stem morphologies (‘Dong Fang Shao Nv’, upright; ‘Lan Tian Piao Xiang’, bending gradually) at five developmental stages were used as materials to investigate the effects of pectin content and nanostructure on straightness using the carbazole colorimetric method and atomic force microscopy observations. The contents of water-soluble pectin (WSP), CDTA-soluble pectin (CSP), and sodium carbonate-soluble pectin (SSP) differed significantly between the two cultivars, and the contents and angle of the flower and branch showed correlations. For the pectin nanostructure, WSP showed agglomerates and long chains, with a higher proportion of broad agglomerates at the later stages of the bending cultivar than the upright cultivar. CSP showed branched chains, and the proportion of broad chains was higher in the upright cultivar at later stages, while CSP shape changed from agglomerates to chains in the bending cultivar. SSP mainly consisted of short linear main chains, and side chains in the upright stem were stacked, and the bent cultivar had more broad and short chains. It can be concluded that the contents, nanometric shape, and size of the three kinds of pectin are highly likely to affect herbaceous peony stem straightness. This study provides a theoretical basis for the role of pectin in the production and breeding of herbaceous peony cut flowers.