Relation between dynamic changes of free amino acid contents in Larix gmelinii needles and injuring factors

Larix gmelinii seedlings under the stresses of cutting needles and caterpillar(Dendrolimus superans) feeding were selected as object for this research.The purpose is to discuss the components and contents of free amino acids with the time which through treatment of cutting needles in different degrees and insect feeding.The change of free amino acid contents in needles was detected by HPLC.The results showed that there were 17 free amino acids in needles.The content of Phenylalanine was at the most,while increased 36.6% in healthy needles on 4 branches after cutting needles compared with control,and increased 98.3% after the treatment of caterpillar feeding 15 days later.The content of total amino acids between induced 25% and 50% in healthy needles had different significance(P0.05) after needles were cut 4 branches 15days later and fed by caterpillar 5 days later,and the variation of total amino acids quantity presented the same trend within 5 days to 15 days by two treatments and at 10 days which is the maximum content induced,.while the total quantity of amino acids after the treatment of caterpillar feeding was higher than cutting needles induced 25%,50% and 75% needles on 4 branches,but had no significant difference.Contents of free amino acids in healthy needles after needles on 4,8 and 12 branches were cut had no significant difference,which showed that larch needles were cut 4 branches could exceed the tolerance threshold and reach defense-induced effects.The contents of many free amino acids decreased and 8 amino acids in undamaged needles changed significantly(P0.05),which were Serine,Glutamate,Glycine,Histidine,Proline,Cysteine,Lysine and Phenylalanine separately.It showed that artificial leaf-cutting ways and larva feeding could induce changes of free amino acids of larch,and affect the growth and development of insects indirectly.