الفهرس 
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Abstract
This study was carried out on the stem galls induced by the gall-midges Rhopalomyia sp. on three important medicinal host plants in St. Katherine Protectorate namely, Seriphidium herba-album, Tanacetum sinaicum and Pterocephalus sanctus.
1. Morphology of plant galls
Galls induced in S. herba-album stems were large, densely white pubescent galls with several chambers, situated on stem sides and one larva developed in each gall. Galls induced in T. sinaicum were open cup-shaped galls. Each gall was composed of a single chamber in which a single larva developed. Galls induced in P. sanctus were knotty irregular-shaped galls. P. sanctus galls were formed of more than one chamber in which one larva developed. S. herba-album galls showed the induction of hairy non-glandular protective tissue covering the whole galls.
2. Micromorphological-induced effects of Rhopalomyia sp. in host plants
Cross sections of non-galled stems in Asteraceae plants S. herba-album and T. sinaicum were similar. Both stems showed typical primary structure. P. sanctus presented a secondary structure of the shoot where vascular bundles eventually collapsed to form a complete ring.
Cross sections of galls in the three studied plants showed the presence of nutritive tissue lining the larval chambers. This feeding tissue showed unique shape of cells as compared to other parts of the gall. The nutritive tissue was composed of small, compacted cells and the innermost cells were bookend-down. Storage parenchymal tissue with large and expanded cells was recorded surrounding the nutritive tissues and/or within empty chambers plants.
Cross sections of galls in studied plants showed the presence of extensive newly developed vascular tissues connecting the stem vascularization with the galls tissues. T. sinaicum and P. sanctus stem galls showed the formation of new vascular tissue within gall tissue to nourish the galls cells.
3. Primary metabolites induction by Rhopalomyia sp. on host plants
3.1 Carbohydrate content in the three studied plants
Carbohydrates were one of the main constituent of both galled and non-galled extracts (mainly stems) of the three studied plants. Galled tissues showed high percentages of carbohydrates in both ethanolic and aqueous extracts except for T. sinaicum. Identified compounds included common sugars, rare sugars, disaccharides and polyols. Identified polyols from the studied plants were mainly myo-inositol derivatives. Galled and non-galled tissues within studied plant could be considered as a source of rare sugars.
3.2 Fatty acid and fatty alcohol content in the three studied plants
Fatty compounds were identified in both galled and non-galled tissues of the three studied plants. Palmitic acid was found in considerably large proportions in galled tissues in the three studied plants extracts.
3.3 Acid content in the three studied plants
Lactic acid, an organic acid, was recorded in very high percentages in the leaf extract of the three studied plants. Phathalic acid was the only identified organic acid in S. herba-album and T. sinaicum galled tissues. Excess phathalic acid activated the antioxidant systems that induced gall formation in an indirect way.
3.4 Amino acid content in the three studied plants
Amino acids and their esters were identified from normal tissues of the studied plants however; they were not recorded in galled tissues.
3.5 Alcohol content in the three studied plants
Alcohols were detected in very low percentages in both galled and non-galled tissues of the three studied except from T. sinaicum galls. 3-Methylene-1,4-butanediol was the only identified alcohol in T. sinaicum galls and was detected in relatively high percentage (18% of the whole ethanolic extract)
4. Secondary metabolites induction in the host plants
4.1 Phenolic content in the three studied plants
Phenolic compounds were the main constituent in both galled and non-galled tissues of the three studied plants. Identified compounds included simple phenols, seven phenolic acids, flavnoides, coumarins, lignans and phenolic glucosides. Brayelin, a coumarin compound, was the main constitute of aqueous extract of S. herba-album stem as it represented 16.32% of the whole extract. Naringenin, a flavonoid compound, was identified only in the gall tissues of S. herba-album and represented 17.22% of the whole aqueous extract.
4.2 Terpene content within normal and galled tissues of studied plants
Terpenes were the main constituent in normal tissues of the three studied plant (mainly S. herba album) and was detected in considerable percentages in galls of T. sinaicum and P. sanctus. One diterpene, represented 13.29% of aqueous extracts of S. herba album stems. Thymol, a monoterpene, was recorded in high percentage (6.5%) in S. herba album leaf aqueous extracts.
4.3 Alkaloid content within normal and galled tissues of studied plants
Alkaloids represented one of the main constituents on both of galled and non-galled tissues in the three studied plant especially T. sinaicum, identified compounds included quinolones, pyrrols, pyrazols, indols, carbazols, pyridines and thiazoles, imazaquin, lysergide, sumatriptan methamphetamine, indols, benzaacridine, morphine, codeine and hydroxynicotinic acid. In S. herba-album, they represented 17%, 21% and 10% of whole aqueous extracts of stem, leaf and gall respectively, while they constituted 27% of the whole ethanolic extract of leaves. They represented 32% and 18% of aqueous extract of T. sinaicum leaves and galls and made up 35% and 27% of the ethanolic extract of leaves and galls respectively. Stems and leaves of P. sanctus recorded considerably high percentages of alkaloids (15% and 22% of the whole ethanolic extract).
4.4 Organometallic content within normal and galled tissues of studied plants
Identified organometallic compounds included molybdenum, nickel, silicon and boron-containing compounds. Silicon-containing compounds were the most abundant compounds especially within S. herba-album leaf ethanolic extract. It represented approximately 50% of ethanolic extract of leaves. Silicon-containing compounds were also recorded from normal tissues of both T. sinaicum and P. sanctus and the galls of T. sinaicum.
Boron-containing compounds (Bo+2) were identified from both normal and galled tissues of S. herba-album and from T. sinaicum galls. Molybdenum-containing compounds (Mo+2) were recorded from normal tissues of the three studied plants and from gall tissues of P. sanctus.
4.5 Amine content within normal and galled tissues of studied plants
Biogenic amines were recorded from the normal tissues of the three studied plants and from the galled tissues of S. herba-album and T. sinaicum.
4.6 Steroid content within normal and galled tissues of studied plants
Steroids were recorded from the normal tissues of the three studied plants and from galled tissues of S. herb-album and T. sinaicum. Identified steroid compounds were mainly mammalian sex hormones which act as precursors influencing plant development as well as gall development.
4.7 Sulfur-containing compounds within normal and galled tissues of studied plant
Sulfur-containing compounds (S-2) were recorded from normal tissues of S. herba-album and T. sinaicum and from S. herba-abum galls. The main role of sulfur-containing compounds was defense against pathogens, thus it played a major role in insect-plant interaction.
4.8 Triazines content within normal and galled tissues of studied plant
Identified triazines compounds included mainly cyanuric acid that was identified from normal tissues of S. herba-album and P. sanctus and galled tissues of T. sinaicum.
4.9 Vitamin content within normal and galled tissues of the studied plants
Vitamin B5 (Pantothenic acid) was the only identified vitamin in the studied plants. It was detected in the ethanolic extracts of T. sinaicum and P. sanctus leaves with high percentages representing 2% and 3.5% of the whole extracts respectively.
4.10 Xylenes, beta-lactans and alkanes content within normal and galled tissues of studied plants
Clavulanic acid, a beta-lactan that represented 6% of ethanolic extract S. herba-album galls.
4.12 Galactoarabinan, lactone, quinone and hydrazine content within normal and galled tissues of studied plants
Hydrazine, a carcinogenic compound, was recorded from aqueous extract of T. sinaicum galls in high percentage (more than 16%) and from normal tissues but in lower percentages (9% of whole aqueous extract of leaves).
4.13 Epipherine and phethalate content within normal and galled tissues of the studied plants.
Epinephrine, a hormone from the adrenal medulla in humans, represented a main consitituent of stem extract of P. sanctus as it represented 14% of the whole aqueous extract.