We studied the effects of exogenous spermidine (Spd) on plant growth and nitrogen metabolism in two cultivars of tomato (Solanum lycopersicum) that have differential sensitivity to mixed salinity-alkalinity stress: ‘Jinpeng Chaoguan’ (salt-tolerant) and ‘Zhongza No. 9’ (salt-sensitive). Seedling growth of both tomato cultivars was inhibited by salinity-alkalinity stress, but Spd treatment alleviated the growth reduction to some extent, especially in ‘Zhongza No. 9’. Exogenous Spd may help reduce stress-induced increases in free amino acids, ammonium (NH4 +) contents, and NADH-dependent glutamate dehydrogenase (NADH-GDH) activities; depress stress-induced decreases in soluble protein and nitrate content; and depress nitrate reductase, nitrite reductase, glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT), glutamate oxaloacetate transaminase (GOT), and glutamate pyruvate transaminase (GPT) activities, especially for ‘Zhongza No. 9’. Based on our results, we suggest that exogenous Spd promotes the assimilation of excess toxic NH4 + by coordinating and strengthening the synergistic action of NADH-GDH, GS/NADH-GOGAT, and transamination pathways, all during saline-alkaline stress. Subsequently, NH4 + and its related enzymes (GDH, GS, GOGAT, GOT, and GPT), in vivo, are maintained in a proper and balanced state to enable mitigation of stress-resulted damages. These results suggest that exogenous Spd treatment can relieve nitrogen metabolic disturbances caused by salinity-alkalinity stress and eventually promote plant growth.
Yi Zhang, Xiao-Hui Hu, Yu Shi, Zhi-Rong Zou, Fei Yan, Yan-Yan Zhao, Hao Zhang, and Jiu-Zhou Zhao
Hai-fei Yan, Xue-jun Ge, Chi-ming Hu, and Gang Hao
Nine microsatellite loci were isolated from Primula obconica using the FIASCO protocol. We used 30 individuals from three populations for the assessment of microsatellite variation. Seven loci were detected with microsatellite polymorphism. The number of alleles per locus ranged from three to seven. The average observed heterozygosity and expected heterozygosity ranged from 0.167 to 0.6 and from 0.409 to 0.653, respectively. These microsatellite markers will be useful to assess the genetic variation and genetic structure of P. obconica.