Study On Responses Of Summer Maize Ecophysiological And Growth Characteristics To Drought Process

Maize is one of the most widely planted crops in the world, and its total yield is the highest among the three major grain crops. In China, the contribution rate of maize total yield increase to national grain yield increase was the highest in recent years. However, the maize yield reduction caused by drought during growing season was even more than the sum of yield reduction caused by other factors. In this thesis, based on the data from summer maize drought manipulation experiment beginning from 7-leaf stage in Gucheng Ecological Environment and Agrometeorological Station in 2013, the responses of maize leaf ecophysiological and growth characteristics to drought occurrence and development were studied. The main conclusions are listed as follows.(1) During the manipulation experiment of summer maize drought occurrence and development, light drought occurred after 15 days of water controlling, and moderate drought happened one month later, extreme drought appeared two months later. Midday depression phenomenon of leaf photosynthesis occurred during the jointing stage under the conditions of light drought. The photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency of the first peace of maize leaf were sensitive to drought, implying they were able to be indicative indices.(2) The photosynthetic rate, transpiration rate and stomatal conductance of maize leaf during growing season decreased significantly with the decrease of soil relative moisture. The difference of all these parameters between water treatments declined with the development of consecutive drought. The water use efficiency showed a rising trend and its difference between water treatments was small at earlier stage, but enlarged at later stage with the aggravation of consecutive drought.(3) The leaf water content decreased linearly with the drought occurrence and development during growing season and it was significantly correlated with soil relative moisture, implying that the leaf water content is able to be an index of crop drought. As to main limiting factor of photosynthesis, there was a conversion process from stomatal limitation to non-stomatal limitation during growing season. The occurrence time of theconversion process was positive related with drought intensity and consecutive time.(4) The leaf SPAD value was not as sensitive as the photosynthetic rate to drought,which reflected its hysteretic nature. Electron transfer rate, photochemical quenching coefficient and photochemical efficiency decreased significantly from filling stage to milk stage.(5) The summer maize stem water content reached the maximum at jointing stage(about93%) and it was not as sensitive as leaf water content to drought. The leaf area index reached the maximum at tasseling stage for the treatment under higher soil relative moisture, while for the treatment under lower soil relative moisture it reached the maximum at filling stage. The specific leaf area declined rapidly in the early stage, while it showed a stable trend. The specific leaf weight showed an opposite trend, and it was significantly higher in the late stage than in the early stage.(6) The summer maize aboveground biomass was sensitive to soil water content, and it decreased with the decrease of soil relative moisture at all stages. The reduction caused by drought at jointing and tasseling stages was obvious. The average daily increase of summer maize aboveground biomass was between 1.15 g to 1.74 g, and the increase rate declined with the decrease of soil relative moisture.