Storage Period and Different Abiotic Factors Regulate Seed Germination of Two Apocynum Species — Cash Crops in Arid Saline Regions in the Northwestern China

Abstract

On degraded land in arid regions, cultivation of Apocynum species can provide significant environmental benefits by preventing soil erosion and desertification. Furthermore, Apocynum venetum and Apocynum pictum, which are mainly distributed in salt-barren lands in the northwestern region of China, are traditionally used to produce natural fiber and herbal tea. Direct sowing of both species may encounter various abiotic stresses such as drought and salinity. However, these effects on germination remain largely unknown, especially for seeds with different storage periods. The aim of this study was to evaluate the effects of storage period, light condition, temperature regime, drought, and salinity on germination performances of both species. Germination experiment was carried out in November 2017. There were four replicates for each treatment, and each petri dish contained 25 seeds. The results indicated that prolongation of storage period significantly decreased the germination percentage and velocity, especially under abiotic stresses. Light did not affect seed germination of A. venetum and A. pictum under any conditions. Seeds had better germination performance at 10/25 and 15/30°C than those of seeds incubated at any other temperatures. With the increase of polyethylene glycol (PEG) and salinity concentrations, seed germination for both species gradually decreased, especially for seeds stored for 2 years. Low PEG (0–20%) and salinity concentration (0–200 mM) did not significantly affect germination percentage of freshly matured seeds. However, long-time storage significantly decreased drought and salinity tolerance in A. venetum and A. pictum during germination stage. For saline soils in arid and semi-arid regions, freshly matured seeds or 1-year-stored seeds of both Apocynum species are recommended to be sown by using drip-irrigation in spring.

Physiological and transcriptional responses of seed germination to moderate drought in Apocynum venetum

“…Apocynum venetum L. (family Apocynaceae) is a perennial semi-shrub species that widely distributed in the temperate zones of Eurasia, North America, northern China, etc., especially in saline-alkali land and sandy soils (Flora of China, 1977;Xie et al, 2012;Rong et al, 2015). The plants can provide significant environmental benefits by preventing land degradation caused by salinization and desertification and offer opportunities to develop desert farming in the arid zones (Ping et al, 2014;Rouzi et al, 2018;Jiang et al, 2021). Meanwhile, it commonly known as "luobuma" in China and has been widely used as a traditional Chinese medicine to treat cardiac disease, hypertension and nephritis, and used for anti-irritability, anticancer and anti-radiation in recent years (Xie et al, 2012).…”

“…In the semi-arid lands, A. venetum plants present flourishing growth because they are easy to propagate and have the ability to withstand the harsh desert environment (Ma et al, 2000;Ning et al, 2010;Jiang et al, 2021). As is known, seed germination is the key stage for the plant life cycle and affects the growth and distribution of plant populations, especially under adverse abiotic conditions (Ren et al, 2011;Campobenedetto et al, 2020).…”

“…In order to find out the effects of abiotic stresses on seed germination of A. venetum, several studies have been conducted on the physiological and biochemical changes. Specifically, the seed germination rate of freshly matured seeds was promoted to some extent under low PEG-6000 (0 to 10%), not significantly affected under low salinity concentrations (0 to 200 mmol/L), while significantly decreased with the increasing of drought and salinity stresses (Zhang et al, 2007;Xu et al, 2015;Jiang et al, 2021); in addition, the seed germination rate was better performance at 10/25 and 15/30 • C (12-h alternating) than any other temperatures, significantly decreased with prolongation of seed storage period, while not affected by the light (Liu et al, 2015;Jiang et al, 2021). For the physiological changes during seed germination in response to drought stress, the contents of electrolyte leakage rates and osmolytes [i.e., MDA, Pro and soluble sugar], and the activities of antioxidant enzymes [i.e., SOD, APX, GR and POD] were increased, while the CAT activity was descended in general trend with the increasing of PEG-6000 concentrations (0-30%) (Xu et al, 2015;Zhao and Dai, 2015).…”

“…To date, seed germination characteristics and physiological changes under drought stress have been conducted, and germination rate promoted under moderate drought has been demonstrated for the psammophytes A. venetum (Zhang et al, 2007;Xu et al, 2015;Zhao and Dai, 2015;Jiang et al, 2021), while the response mechanism to drought stress is still unknown. In this study, the difference of the seed germination characteristics and the changes of antioxidant enzyme activity, osmolytes content and genes expression…”

Total Flavonoids Extracts of Apocynum L. from the Ili River Valley Region at Different Harvesting Periods and Bioactivity Analysis

“…In China, Apocynum plants are mainly grown in Xinjiang Uygur Autonomous Region, especially in the area where agriculture is severely limited by soil salinity, alkalinity, and drought, owing to the plant’s excellent tolerance to stresses [ 17 ]. The Ili River Valley Region in the northwestern part of Xinjiang is the wettest [ 18 ].…”