A 30‐day experiment was performed to investigate the effects of bioflocs on water quality, and survival, growth and digestive enzyme activities of the white shrimp Litopenaeus vannamei. Altogether 28 shrimp (7.4 ± 0.1 g) were stocked in each 150 L tank. Two bioflocs treatments and one control were managed: ‘bioflocs 1’ and ‘bioflocs 2’ based on two different densities of the bioflocs, and clean water control without the bioflocs. Brown sugar was added to the bioflocs 1 and bioflocs 2 treatment tanks accounting for 28% and 80% of the shrimp feed respectively (corresponding to proximate C/N ratios of 10 and 14 in daily additions of organic matter respectively), so as to promote bioflocs production and approximately 14 mL L−1 in treatment bioflocs 1 and 20 mL L−1 in treatment bioflocs 2 were maintained from day 15. Monitoring of selected water quality parameters throughout the whole experiment period showed that all parameters remained within recommended levels for shrimp culture in the bioflocs treatments at zero‐water exchange, especially low total ammonia nitrogen and nitrite nitrogen levels. By the end of the experiment, shrimp survival rates were above 86%, with no significant differences (P > 0.05) among the three groups. Both weight gain rate and special growth rate tended to increase in the bioflocs treatments compared to those in the control. Meanwhile, the overall specific activities of protease, amylase, cellulase and lipase of the shrimp in the bioflocs treatments were all higher than those in the control; and for the specific activity of the same digestive enzyme, the differences between the bioflocs treatments and the control performed inconsistently among different organs: hepatopancreas, stomach and intestine. Present results suggest that the bioflocs can not only maintain favourable water quality conditions for shrimp culture and help shrimp grow well in zero‐water exchange culture systems, but may also have a positive effect on digestive enzyme activities of the shrimp.

Endophyte-mediated salinity tolerance is largely unknown in tall fescue [Schedonorus arundinaceus (Schreb.)]. The experiment was designed to characterize growth, ion accumulation, and antioxidant metabolism of tall fescue infected by the endophyte Epichloë coenophiala to different levels of salinity stress. Endophyte-infected (E +) and endophyte-free (E−) tall fescue (cv Kentucky 31) plants were exposed to 10 d of 0 (unstressed control), 100 and 200 mM NaCl treatments in a greenhouse, respectively. Salinity stress caused reductions in plant height, leaf fresh weight (LFW), leaf dry weight (LDW), and leaf water content (LWC), and increased Na + concentration, but E + plants had significantly higher LFW, LDW, and LWC under both NaCl treatments and lower Na + than E− plants under 200 mM NaCl. Salinity stress decreased K + and Mg 2+ and did not alter P, and increased Ca 2+ in E + plants and caused no change in Ca 2+ in E− plants; however, endophyte had no effects on these elements. Chlorophyll fluorescence (Fv/Fm), malondialdehyde (MDA) concentration, and activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) remained unchanged in E + plants, but Fv/Fm was reduced and MDA level and enzyme activities were elevated in E− plants under 200 mM NaCl, where E + plants had significantly higher Fv/Fm and lower MDA, SOD, and APX activities than E− plants. Peroxidase activities increased in E + plants under 200 mM NaCl and in E− plants under both NaCl treatments. The results indicated that endophyte promoted salinity tolerance in tall fescue through maintaining higher growth and photochemical efficiency and lowering Na + accumulation and lipid peroxidation. The significantly induced antioxidant enzyme activities and lipid peroxidation in E− plants suggested a possible enhanced oxidative injury in endophyte-free plants exposed to a high level of salinity stress.