Physiological characters and yield formation of corn (Zea mays L.) under waterlogging stress in jointing stage

Maize jointing stage is an important period for reproductive growth and vegetative growth and also in this stage, corn is sensitive to waterlog. In the study area in the jointing stage of corn, frequent waterlog in field often occur causing damage of corn yield. Therefore finding out the upper threshold for number of days that corn can endure waterlog, and understand the corn physiological reaction after flooding can help to develop management tools to improve corn production. The bottomless pit measurement was set at different waterlogging days (1, 2, 3, 5, and 7 d) to determine the corn response to waterlogging duration and the effect of waterlogging duration on corn growth, grain fill, dry mater distribution and yield characteristics. At the vegetative growth stage, the results showed that the average plant height of corn with 1, 2, 3, 5, and 7 days of waterlog was reduced by 2.26%, 2.26%, 2.45%, 11.36% and 10.17%, respectively, and the LAI (leaf area index) was decreased respectively by 23.79%, 18.93%, 13.04%, 32.74% and 34.27% as compared with the CK (control treatment). With the waterlogging duration more than 5 days at the jointing stage, the plants became dwarf and the leaves turned yellow. For plant physiological response, three days after each flooding duration test showed that chlorophyll content of leaves with the flooding duration of 1, 2, and 3 days was higher (p<0.05) than CK, and root activity increased. But the chlorophyll content of leaves and root activities of flooding duration of five and seven days decreased as compared to the CK. The result also showed that with the flooding duration more than 5 days, chlorophyll content of leaves from corn filling stage to milk-ripe stage was 10.87% lower (p<0.05) than that of the CK. Therefore once the waterlogging duration was more than five days at the jointing stage, chlorophyll content of leaves would stay lower and not be recovered. For the reproductive growth stage, flooding duration at the corn jointing stage affected the grain quality of post filling. The result indicated that compared with the CK, the grain yield of waterlogging duration with 1, 2, and 3 days was rather similar, but with 5 days, it was lower (p<0.05) and it was the lowest with flood duration of 7 days. The ear rows and ear width of corn decreased with the increase of the number of days of flooding, but it was not significantly different as compared to the CK. The corn ear tip-barren had significant difference (p<0.05) than the CK. The corn ear tip-barren from waterlogging duration of 1, 2, 3, and 5 days was about two times higher than the CK, the flooding duration of the 7 days was five times higher than the CK. The ear length, ear weight, ear grain weight and hundred-grain weight of corn decreased as the waterlogging day increased. The yield of corn with 1, 2, 3, 5, and 7 waterlogging days were reduced by 16.58%, 16.65%, 26.11%, 34.32% and 39.01%, respectively. Therefore waterlogging duration over 5 days not only affected the normal growth of corn, but also reduced the yield significantly. The research provided information for waterlogging monitoring, fast evaluation of damage and waterlogged field drainage standard determination.