Keywords: 
• seedless litchi A4 /
• physiological fruit drop /
• regular pattern /
• dynamic observation

Abstract: T Trees of seedless litchi A4（Litchi chinensis Sonn.） of 10 years old were used as the experimental material to regularly observe their physiological fruit drops during the fruit growth and development after blossom fall.During the whole process of fruit development,the seedless litchi A4 showed four fruit-dropping peaks which appeared at 9 to 12 days,21 to 27 days,39 to 42 days and 51 to 60 days（before harvest）,respectively,after blossom fall.Among the four stages of physiological fruit drop,the number of dropped fruits was significantly higher at the first time stage than at the other three stages.However,the rate of fruit drop at the pre-harvest stage was up to 69.84%,which was significantly higher than that at the other fruit drop stages.The abscission site of physiological fruit drop at the four stages was consistent,and the fruits all fell from the union between the flower axis and the subaxis at the end of the fruit stem.The numbert of single fruit drop was 20% higher than that of paired fruit drop,and the yellow fruit（fruit peel color turned yellow） was dropped 3.65 times higher than that the red fruit.Moreover,the yellow fruits were lower in transverse diameter,longitudinal diameter and single fruit weight than the red fruits.In this context,the pre-harvest fruit drop was the main factor of the yield loss for the seedless litchi A4.The small fruit was readier to drop when the fruit skin just turned yellow.In the future,attention should be focused on the regulation of the last two stages of fruit drop in cultivation,especially the pre-harvest fruit drop.