Relationship of quality formation and ultrastructure of cotyledon cells in two quality types of peanut

Abstract

Aims There are great differences in yield and quality of different quality types of peanut(Arachis hypogaea),and there is a significant negative correlation between different quality traits in one cultivar.We conducted an experiment to study the differences of quality formation and cell ultrastructure in different quality types of peanut.Methods A high-protein variety,'XB023',and a high-fat variety,'Luhua 9',were planted in an agricultural experiment station field with a randomized block design in the 2010-2011 growing season.We observed the protein,fat and soluble sugar content of seeds while the pegs grew into the soil for 10-60 days,the components of amino acids and fatty acids and the changes of ultrastructureincotyledoncellsduringdifferentdevelopmentphases.Important findings The protein content of 'XB023' was lower than that of 'Luhua9' in the earlier stage of seed development,but significantly higher in the late development phase.The essential amino acid contents of 'XB023' were higher than those of 'Luhua 9',with glutamate,lysine and leucine contents being significantly different.Accumulation of fat in 'XB023' was lower than that of 'Luhua 9' throughout the development phases,and fat content of 'XB023' decreased in the late stage.The content of soluble sugar and the oleic/linoleic(O/L) ratio of 'XB023' were significantly lower than in 'Luhua 9'.Starch grains,lipid bodies and protein bodies in cotyledon cells of the two varieties had begun to form while the pegs grew into the soil 10 days.With the number of lipid bodies and protein bodies increasing ceaselessly,the size of starch grains increased at first and then narrowed gradually with cotyledon development.The time when lipid bodies of 'XB023' reached maximum size was earlier than that of 'Luhua 9',and the time of rapid accumulation of lipid bodies in 'Luhua 9' was longer than that of 'XB023'.The protein bodies of the two varieties both reached the maximum size when the pegs grew into the soil for 40 days.The number of protein bodies of 'XB023' grew fast during the late period.The protein content of seeds was determined by size and number of protein bodies,and the fat content was mainly determined by the number of lipid bodies in the cotyledon cells.