Adventitious Roots and Secondary Metabolism

Plants are a rich source of valuable secondary metabolites and in the recent years plant cell, tissue and organ cultures have been developed as an important alternative sources for the production of these compounds. Adventitious roots have been successfully induced in many plant species and cultured for the production of high value secondary metabolites of pharmaceutical, nutraceutical and industrial importance. Adoption of elicitation methods have shown improved synthesis of secondary metabolites in adventitious root cultures. Development of large-scale culture methods using bioreactors has opened up feasibilities of production of secondary metabolites at the industrial levels. In the present review we summarize the progress made in recent past in the area of adventitious root cultures for the production of secondary metabolites.

Micropropagation of yellow mangosteen:a valuable endemic tree of India

We developed a method for in vitro regenera- tion of Garcinia xanthochymus （yellow mangosteen） from matured seed segments. Multiple shoots were induced on woody plant （WP） medium supplemented with cytokinins. An average of 11 shoots per explant were regenerated from mature seed segments on WP medium containing 20 μM 6-benzylaminopurine. Histological analysis revealed that hypodermal cells of seed segments were initially involved in active division, which later developed into meriste- moids, subsequently leading to the formation of shoot buds. Shoot elongation was achieved by repeated subculturing of seed explants in shoot regeneration medium. Rooting of shoots was achieved on WP medium supplemented with indole-3-butyric acid or s-naphthalene acetic acid. Plant- lets were transplanted to pots containing soil： compost （1：1） and survival rate was 90 %.

Distribution of gymnemic acid in various organs of Gymnema sylvestre

The gymnemic acid contents in various organs of Gymnema sylvestre were investigated by High Performance Liquid Chromatography (HPLC) method. The results shows that the content of gymnemic acid in various organs, obviously different, was 54.29, 31.66, 28.82, 27.67, 25.39, 20.56 and 1.31 mg·g-1 DW in shoot tips, flowers, nodes, leaves, internodes, roots and seeds, respectively. The highest gymnemic acid content (54.29 mg·g-1 DW) was found in shoot tip, 1.96 fold higher than that in leaves (27.67 mg·g-1 DW). Maximum quantity of gymnemic acid (35.39 mg·g-1 DW) was observed in the young leaves, which was 1.52 times higher than that in old leaves (23.07 mg·g-1 DW). The content of gymnemic acid in young, middle and old internodes was 26.47, 25.77 and 23.94 mg·g-1 DW, respectively, all lower than that in leaves (27.67 mg·g-1 DW), whereas the content of gymnemic acid in young, middle and old nodes was 27.96, 28.81 and 29.66 mg·g-1 DW, respectively, all higher than that in leaves. The study provides the scientific evidences for the rational development and utilization of Gymnema sylvestre resources, since over exploitation of natural stands has caused depletion of these plants in nature.

Estimation of phenotypic divergence in a collection of <i>Cucumis melo</i>from Kerala State, Southern India

A collection of melon (Cucumis melo L.) from Kerala state, Southern India, consisting of thirty three accessions was evaluated for 22 quantitative and 14 qualitative characteristics to estimate the phenotypic diversity. The collection showed appreciable phenotypic diversity in fruit related traits. Principal component analysis (PCA) was performed to determine the relationships among the populations. The analysis revealed that the variations in stem hair length, number of nodes per plant on 60th day, fruit shape, fruit length, fruit weight, fruit colour at ripening, fruit rind hardness, flesh colour, flesh firmness, quality of flesh, shelf life, seed colour were the principle characters to discriminate melon accessions evaluated in the present study. When the 33 populations were plotted on the first two principal components, accounting for 49.97% of the total variation, three clusters were identified, accounting for 36 morphological attributes used in the study. The greater part of diversity was accounted for fruit diameter, fruit weight, fruit length and width, fruit cavity length and diameter, seed length and colour. Flesh area of fruit, flesh thickness, leaf size, seed weight, seed index did not account for variation in the first six principal components of the melon collection. Scatter diagram segregated the acidulus and momordica into different clusters. This evaluation of fruit trait variability can assist geneticists and breeders to identify populations with desirable characteristics for inclusion in various breeding programmes.