The Response of Photosynthetic Functions of F1 Cutting Seedlings From Physocarpus amurensis Maxim (♀) × Physocarpus opulifolius “Diabolo” (♂) and the Parental Seedlings to Salt Stress

Abstract

This paper selected clonal cutting seedlings from the F1 hybrid varieties of Physocarpus amurensis Maxim (♀) × P. opulifolius “Diabolo” (♂) as research material to study the response of the photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of P. amurensis hybrids and their parental leaves to NaCl stress (with concentrations of 0, 50, 100, and 200 mmol⋅L-1). The results showed that under salt stress, the stomatal conductance (Gs), transpiration rate (Tr), and net photosynthetic rate (Pn) of the three kinds of P. amurensis all significantly decreased. When the NaCl concentration was below 100 mmol⋅L-1, the intercellular CO2 concentration (Ci) of leaves of the three samples declined with the increase of salt concentration; however, when the concentration increased to 200 mmol⋅L-1, Ci did not decrease significantly, especially when the Ci of P. opulifolius “Diabolo” presented a slight increase. This indicated that the decline of photosynthetic carbon assimilation capacity induced by salt stress was the consequence of interaction between stomatal factors and non-stomatal factors, and the stomatal factors played an important role when the salt concentration was below 200 mmol⋅L-1. Compared with P. amurensis, the photosynthetic gas exchange capability of P. opulifolius “Diabolo” leaves was more sensitive to salt stress, and the limitation of non-stomatal factors was relatively evident. However, the photosynthetic capacity of hybrid P. amurensis leaves with the desired purple color was improved compared with P. amurensis. Under salt stress, the PSII activity of the three kinds of P. amurensis leaves declined, the electron transfer was inhibited, and obvious signs of photoinhibition were present. The PSII activity of P. opulifolius “Diabolo” leaves was more sensitive to salt stress than that in P. amurensis. Under salt stress, the NPQ of P. opulifolius “Diabolo” leaves decreased greatly, while under high salt concentrations the degree of photoinhibition in P. amurensis and hybrid P. amurensis were reduced due to a relatively high NPQ. With the increase of salt concentration, the Vk of P. amurensis and hybrid P. amurensis leaves presented a decreasing trend. However, the Vk of P. opulifolius “Diabolo” leaves increased slightly. This suggested that the effects of salt stress on the oxygen-evolving complex (OEC) of the three P. amurensis sample types were relatively limited and only the OEC of P.s opulifolius “Diabolo” leaves were slightly sensitive to salt stress. The VJ of all leaves from the three P. amurensis types increased under salt stress, and the VJ increased significantly when the salt concentration increased to 200 mmol⋅L-1, indicating that salt stress obviously impeded the electron transfer chain from QA to QB on the PSII receptor side. Moreover, high salt concentrations caused thylakoid membrane dissociation. The electron transfer and degree of damage to the thylakoid membrane of P. opulifolius “Diabolo” leaves were obviously higher than that of P. amurensis. However, the electron tr...

Nitric Oxide Is Associated With Heterosis of Salinity Tolerance in Brassica napus L.

“…In this study, we found that the hybrid of B. napus resulted in the promotion of seed germination and seedling growth under salt stress (Figures 1A-D), which were confirmed by the alleviation of reduction in plant height (Figure 1E), chlorophyll (Figure 1F), relative water content (Figure 1G), and biomass (Figure 1H). These results in B. napus were consistent with previous studies (Akram et al, 2010;Fujimoto et al, 2012;Bagum et al, 2017;Xu et al, 2018), showing that hybrid plants were more tolerant against salinity.…”

“…Improved germination was observed in the hybrid plant of chickpea because of its reduced ROS level (Pandey et al, 2019). In addition, hybrids showed obvious heterosis for photosynthesis under salt stress (Xu et al, 2018). However, very little is known about the corresponding mechanisms regarding heterosis of salinity tolerance in plants.…”

“…hybrid plants confer increased salt stress tolerance partly by maintaining ion homeostasis, showing a lower Na + /K + ratio in the stressed hybrids than parental lines (Figures 2E-G). Further experiments regarding kinetic changes in K + retention and Na + exclusion and the corresponding mechanism related to NO signaling (Pérez-Alfocea et al, 1996;Zhao et al, 2004Zhao et al, , 2007Xu et al, 2018;Farooq et al, 2020) should be carried out in the near future.…”

“…Many investigations regarding the tolerance mechanisms underlying heterosis of salinity tolerance have been reported (Akram et al, 2010;Fujimoto et al, 2012;Bagum et al, 2017;Xu et al, 2018;Farooq et al, 2020). However, the role of NO in heterosis has been rarely considered.…”

“…It is understood to be the sum of multiple physiological and phenotypic traits, including changing flowering time and rate of botanic growth, increased biomass accumulation and yield, and resistance to biotic and abiotic environmental stresses (Lippman and Zamir, 2007;Baranwal et al, 2012;Ko et al, 2016;Feys et al, 2018). Importantly, heterosis is observed when plants are subjected to salt stress (Pérez-Alfocea et al, 1994;Xu et al, 2018). However, the traditional dominance and overdominance genetic models do not sufficiently explain the entire spectrum of growth and stress tolerance characteristics of heterosis in crop plants (Lippman and Zamir, 2007;Birchler et al, 2010;Krieger et al, 2010;Goff, 2011;Schnable and Springer, 2013).…”