| Jiao-Gu-Lan [Gynostemma pentaphyllum (Thunb.) Makino], which belongs to Subgen. Gynostemma, Gynostemma, under Cucurbitaceae, is a perennial climbing herbal liana growing wild throughout tropical Asian, China, Korea and Japan. Gypenosides are the major medicinal components that are extracted from the leaf, stem, rhizome and root of this herb.After reviewing systematics, distribution, morphorlogy and structure, growth and development, physiology and ecology, chemical component, pharmacology, medical exploitation and comprehensive use, the technique of propagation and cultivation, we investigated the structure of the vegetative organs of G pentaphyllum and its correlation with medical components by using anatomy, histochemistry and phytochemistry. The structure and content of total gypenosides among 6 species of Gynostemma were also compared. By using physiological and ecological methods, the changes of leaf morphology, structure and photosynthetic characteristics, and gypenosides content under different shading treatment were described, and the coenology features of wild Gynostemma in two plots in Northwest Hunan province were investigated.The leaf of G pentaphyllum was bifacial, with distinct differentiation of palisade tissue and spongy tissue, and there was a single vascular bundle in mid rib, 5 vascular bundles in leaf stalk. The transverse section structure of stem was composed of epidermis, cortex and vascular cylinder. 9 bicollateral vascular bundles arranged in 2 rings were separated from one another by broad strips of ground tissue. There was a continuous ring of perivascular fibrous cells in the pericycle of stems, but this may become discontinuous in rhizomes. The rhizome had secondary structure. Primary xylem in young rootwas diarch, triarch or tetrarch, then second structure existed in old root.Ultrastructures were studied by transmission electron microscope. There was substance translocation in the sieve elements by some bubbles, but no evidence confirmed whether these substances in bubbles were gypenosides or not, for no special electron density bodies or osmiophilis granules related to gypenosides were seen in sieve elements, as did in assimilating tissue and phloem parenchyma.Histochemistry test in the vegetative organs showed that vanillin-acetic acid and perchlorid acid (1:1) reacted with ginsenosides-like substance to produce characteristic colors, from light red to purple. We used it as a test reagent to locate gypenosides and deduce its contents. Gypenosides were stored in palisade tissue and spongy tissue in leaf, the undifferentiated assimilating tissues appeared redder than the mature ones, and the effete leaf accumulated no gypenosides. The assimilating tissue, external phloem contained more gypenosides than epidermis and collenchyma, while the xylem and pith parenchyma contained no gypenosides. Epidermal hair and glandular hair had gypenosides also. The younger the organs were, the redder they developed. In rhizome and old root, gypenosides accumulated in secondary phloem and phelloderm.The contents of total gypenosides changed with seasons in a growth period. It showed a changing trend from low to high, then to low, during the period from vegetative growth, florescence and fructescence to withering. It was lowest in June, increased from July to September, reached the highest value in October, and dropped in November to the value of July to August. The content of total gypenosides in rhizome was significant higher than that in leaf and stem, leaf was higher than stem, younger organs were higher than older ones, male was higher than female. The total yield of gypenosides of tetraploid was higher than that of diploid. It was suggested that cultivating tetraploid G pentaphyllum and male plants more, harvesting the aerial parts only, and remaining the rhizome and root in florescence and fructescence (Sept. to Oct.) was of benefit to improving both herbal quality and quantity, and accelerating the sustainable utilization of wild resources.The structure features of stem and leaf of 6 species of Gynostemma were similar, with quantity difference in anatomic index, but no specific propertyto species. There was no significant correlation between the contents of total gypenosides and the structure index including the ratio of thickness of epidermis and cortex to stem diameter, palisade tissue to spongy tissue, vascular bundle area to stem area, external phloem area to stem area. G guangxiense, G. pentaphyllum, G cardiospermum and G. laxum had higher contents of total gypenosides than G. longipes and G. pentagynum did.The daily patterns of net photosynthetic rate (Pn) appeared as double-peak curves. The peak values appeared at 11:00 am. and 17:00 pm. There was a distinct phenomenon of "noon break" under strong light and high temperature. G pentaphyllum is a species of sciophiles. The leaf morphology and structure were largely affected by light intensity. Under shading treatments, the leaf featured with large size, dark green, thin thickness of leaf blade, palisade tissue and spongy tissue, and undeveloped vascular bundles compared with those under full sunlight. Meanwhile, the contents of chlorophyll and net photosynthetic rate under shading treatment were higher than those under full sunlight, while the contents of total gypenosides showed a reverse trend to the former. Shading treatment could accelerate the growth and development of G. pentaphyllum, thus increase the field yield and total gypenosides.There are 3 species of Gynostemma in Northwest Hunan province, including G pentaphyllum, G. laxum and G. pentagynum, all growing in shady and moist mountainous environment. Ficus heteromorpha, Camellia candata and Weigela japonica var. smica were mainly trees shading the community. The concomitant community of Gynostemma consisted of 158 species, 134 genera, 70 families of vascular plants, showing a higher index of diversity. Chrysosplenium lanuginosum and G pentaphyllum, as well as G. pentagynum and Artmisia lavanduaefolia were dominant species in the concomitant community of G. pentaphyllum and G. pentagynum respectively. Pilea notata was an important companion species for G pentaphyllum and G pentagynum. |
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