Study On Anatomical Structure And Histochemical Localization Of Immature Insect Gall Of Leptocybe Invasa Fisher & La Salle

The mechanism of insect gall formation remains unknown,anatomical structure of insect gall and physiological and biochemical changes of eucalyptus in leaf and insect gall had been studied,however,there are not reports about histochemical localization of insect gall.The feature of morphology and structure of immature insect of Leptocybe invasa Fisher&La Salle in petiole of eucalyptus clones DH201-2,and their metabolites localization were investigated using anatomy and histochemistry methods in this paper.These researches aimed at giving probative value for formation mechanism of insect gall in eucalyptus,deepening the understanding of relationship between Leptocybe invasa and eucalyptus and providing scientific and theoretical basis for control of Leptocybe invasa Fisher&La Salle.The results showed that the anatomical structure of normal petiole consisted of epidermis,cortex,vascular bundle and pith,Leptocybe invasa Fisher&La Salle parasitized near the vascular tissue,where formed gall room,the gall room consisted of three layers,they were respectively outer layer,nutritive tissue and gall hole,from outside to inside.Lipid droplets were not detected in the cells of the cortex and vascular bundles of the non-galled petiole and the first stage gall,but in both the second stage and the third stage galls,a few lipid droplets were observed in the cells of cortex and gall room,the cell walls of epidermis were strongly stained.Starch was distributed in the cells of pith and cortex near the vascular bundles of non-galled petiole;in the immature galls,they dispersed in the cells of cortex,and starch grains in non-galled tissue were more than immature gall.In non-galled tissues,the histochemical reaction to proteins was more intense in the cells next to epidermis;in immature galls,a centripetal gradient of proteins was established,protein content in cells of gall room was the most.In both non-galled petiole and immature gall,calloses were only detected in cells of epidermis,the reaction for calloses was negative for other tissues.Acid invertase activities were labeled in non-galled petiole and immature galls of all developmental stages.This enzyme activity was more intense in parenchymal cells of vascular bundles and cortex parenchymal cells near vascular bundles of non-galled petiole,in immature gall,acid invertases were accumulated in the cortex parenchyma cells,xylem parenchyma and phloem parenchyma,acid invertase activities in the cells of gall room were the highest.Nucleic acid was histochemically distinct in qualitative and distribution sites of reaction in non-galled and immature gall tissues.Nucleic acid was detected in cortex and vascular bundles of non-galled petiole,but the content was few.In immature gall,nucleic acid was detected in cortex,vascular bundles and gall room,among which the cells of nutritive layer of gall room was strongly stained,and the DNA and RNA qualitative of parenchymal cells increased with the immature gall development.The results of localization of phytohormones showed that IAA,GA3 and ZR were little and equally distributed in non-galled petiole,in immature gall,IAA,GA3 and ZR were mainly accumulated in nutritive layer cells of gall room and the density of the GA3 in the cells of epidermis,cortex and vascular bundles was higher than IAA and ZR.Soluble sugar contents in non-galled petiole were obviously higher than immature gall.Abased on the above research,synthesized analysis the anatomical structure of immature insect of Leptocybe invasa Fisher&La Salle and changes of its metabolites accumulation,Leptocybe invasa induced hyperplasia of parenchyma cells in eucalyptus tissue and the formation of gall room,the larva of Leptocybe invasa lived in the centre of gall room and fed off tissues around,leading to the accumulation and distribution change of metabolites(protein,starch,lipid,nucleic acid,acid invertase,phytohormone and so on)in eucalyptus.