No abstract

Machine transplantation results in serious transplant shock in seedlings and results in a longer recover stage, which negatively impacts the growth of low-position tillers and the yield of machine-transplanted rice. A barrel experiment was conducted to examine the effect of the foliar application of triacontanol (TRIA) on machine-transplanted rice during the recovery stage. TRIA (0, 1, 5, and 10 μM) was sprayed over leaves 2 days before transplanting. The chlorophyll content, sucrose content, oxidative damage, antioxidant enzyme levels, glutathione (GSH), and ascorbate (ASA) redox states, tiller dynamics and yield components of the plants were investigated. The results show that foliar-applied TRIA significantly alleviates the growth inhibition and oxidative damage caused by transplant shock. Furthermore, the application of TRIA increased the chlorophyll and sucrose contents of the plants. Importantly, TRIA not only significantly improved the activity of catalase (CAT) and guaiacol peroxidase (POD), demonstrating that POD can play an important role in scavenging H2O2 during the recovery stage, but it also enhanced the redox states of ASA and GSH by regulating the activities of enzymes involved in the ASA–GSH cycle, such as ascorbate peroxidase (APX) and glutathione reductase (GR). A dose of 10 μM TRIA was the most efficient in reducing the negative effects of transplant shock, increasing the panicles, grain filling, and grain yield per hill by 17.80, 5.86, and 16.49%, respectively. These results suggest that TRIA acts to reduce transplant shock in association with the regulation of the redox states of ASA and GSH and antioxidant enzymes and serves as an effective antioxidant to maintain photosynthetic capacity and promote the occurrence of low tillers.

Looming labor shortages and lower efficiency demand a shift from the cultivation of seedlings via the traditional nutritive soil method (CK) to hydroponically grown long‐mat seedlings (HLMS), a new method of raising rice (Oriza sativa L.) seedlings. This study was conducted to investigate the seedling quality and field growth characteristics of HLMS. We examined the effect of HLMS on seedling quality, mechanical transplantation quality, field growth characteristics, yield and benefit/cost ratio compared with those of CK (as a control). A widely grown conventional japonica rice cultivar (Wuyunjing24) and an indica hybrid rice cultivar (6Liangyou9368) were used as test material. The HLMS and CK showed no significant differences in weight/height ratio, seedling emergence rate, N content of leaves or antioxidant enzyme activities after transplantation; however, HLMS exhibited a more vigorous root system, a significantly decreased leaf area index and an extended transplantation period. The mechanical transplantation quality of HLMS was similar to that of CK but showed a significantly improved force of root entanglement. Compared with CK, the dry matter accumulation of HLMS differed quite low at the early field growth stage, whereas increased rapidly at the late growth stage. The yield and benefit/cost ratio of HLMS were equivalent or superior to those of CK. Briefly, the seedling quality of HLMS was better than that of the control, and its mechanical transplantation quality was comparable to that of the CK, enabling high‐yield and high‐efficiency rice production.Core Ideas Hydroponically grown long‐mat rice seedlings is a novel seedling cultivation method that reduces labor costs and improves efficiency. The force of root entanglement of hydroponically grown long‐mat rice seedlings was significantly improved. The yield and benefit/cost ratio of hydroponically grown long‐mat rice seedlings were equivalent or superior to those of the control.