| Coix1401 is a novel and wild type feeding grass, which has diverse abiotic tolerance abilities, especially for waterlogging. Performing comprehensively characteristic identification of waterlogging tolerance ability not only provides theoretical basis for experimental demonstration and cultivar certification, but also benefits for understanding the genetic basis of waterlogging. Main results are as follows:(1) The plant height (PH), dry weight (DW), root surface area (RSA), root vitality (RV) and tillering were measured as the index of water logging for two Coix (YY1 and YY8), one teosinte (TZ04) and one maize inbreed line (Mo 17). YY1 has the highest average water logging indexes (0.726), while that of YY8, TZ04 and Mo 17 were 0.680, 0.518 and 0.394, respectively. YY8 has the highest PH; TZ04 has the highest shoot dry weight (SDM); while YY1 has the highest RSA, RV and tillering. During each treatment phase, YY1 showed not significantly suppressed increasing for PH, DM, RSA and RV. The PH increasing of TZ04 and Mol7, the SDW increasing of YY8, TZ04 and Mo 17, and the RSA increasing of YY8 were suppressed significantly when suffered from water logging for 10-20d. In addition, the RVs of YY8 and TZ04 were also decreased during the 10-30d water logging stage.(2) The activity of SOD, CAT and the concentration of MDA in leaves, and the activity of PDC and ADH in roots of YY1 and TZ04 were measured. YY1 had the activity peak of SOD (9.96 U/g) when suffered from waterlogging for 12h while the peak (8.95 U/g) occurred to TZ04 after 48h under treatment condition. YY1 also showed the activity peak of CAT (1103 U/g) when water logged 6h while TZ04 had the peak (775 U/g) suffered more 6h-treatment than YY1. As to the concentration of MDA, YY1 showed a stable concentration (18.26 nmol/g) trend after 12h-treatment, and on the contrary, the concentration in TZ04 were fluctuating, especially twice increasing and reducing happened during the 48h-treatment. As for PDC activity, it was almost stable during the early stage (0-12h), and then (24-48h) dramatically increased to 0.73 U/g in YY1. However, it was gradually increasing to 0.69 U/g in TZ04 during 0-48h logging. The activity peak of ADH in YY1 (0.29 U/g) was appeared at a very early stage (6h), while that in TZ04 (0.08 U/g) was appeared later than YY1 (12h).(3) We also compared the structure of different roots of YY1 under waterlogging. Pneumatophore's structure is complete, which has epidermis, corter, endodermis, xylem, phloem. Impressively, the ratio of aerenchyma to corter in pneumatophore was 21.44%, which was significant more than that in adventitious roots. Moreover, the ratio of xylem to stele was 77.39%, which was also significant more than that in adventitious roots.(4) Pneumatophore primordium originate from pericycle cells. And pericycle cells have several pneumatophore primordius in the same small area.(5) In addition, we found that ethylene was produced in YY1 when under water logging, and when exogenous 1-MCP was added into the water, the total root length was reduced by 18%, the root tips was reduced by 22%, while the average root diameter was increased by 16%, resulting in the total root surface not changing significantly.The above results suggest that, the water logging tolerance of YY1 is better than YY8, TZ04 and Mo 17, which may result from rapidly response of antioxidant enzymes, anaerobic respiration enzymes and advanced pneumatophore. The architecture of the pneumatophore was complete but different from adventitious roots. Pneumatophore primordium originate from adventitious root's pericycle cells, ethylene was induced in YY1 under water logging; and the root number of YY1 was reduced and the average root diameter of YY1 was increased when suffered from water logging and exogenous 1-MCP. |
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