Changes in Soluble Sugars, Sugar Profile, Starch and Proline in Developing Coconut (Cocos nucifera L.) Inflorescences
Abstract
Changes in soluble sugars, sugars profile, starch and proline levels in inflorescence rachillae from individual coconut palms were investigated during inflorescence development with the aim of determining a possible correlation between these characters and morphogenic potential of inflorescence tissues. Rachillae for analysis were collected from unopened inflorescences of -1 to -13 stages (considering the youngest open inflorescence as 0 stage) in decreasing order of maturity (–1 stage is the most mature stage whereas –13 is the most immature stage). Important differences among the maturity stages were observed for total sugars. In very tender inflorescences (-13 and -12), the total sugar content was very low whereas a gradual increase was observed from -11 to -7 stages, with -7 stage having the highest level. The total sugar content in more mature inflorescences was relatively low, with the exception of -2 stage, which had a high total sugar content. In regard to sugar profiles, sucrose, fructose and glucose were the main soluble sugars present in coconut inflorescence and sucrose was the most abundant sugar in -5 to -9 maturity stages. Total soluble sugars and sucrose in maturity stages from -5 to -9 showed a very similar variation and significantly higher levels of sucrose were observed in -6 to -8 stages. The proline content in the mature stages, -1 to –3, was significantly lower than in the other stages with no significant variation in the stages –4 to –11. The pattern of variation in starch content was similar to that of proline which decreased with increasing maturity of inflorescence. In view of the results obtained, the higher accumulation of sucrose and total sugars in -6, -7 and -8 stages may have some significance in morphogenesis, especially as an energy source. The 10 cm length inflorescence that responds better for callusing falls within this range. Thus total sugar and sucrose content may be possible biochemical markers for assessing the morphogenic potential of inflorescence explants.
References
Bernier, G., Havelange, A., Houssa, C., Petitjean, A., and Lejeune, P. (1993) Physiological signals that induce flowering. Plant Cell 5: 1147-1155
Branton, R. L. and Blake J., (1983) Development of organized structures in callus derived from explants of Cocos nucifera L. Annals of Botany 52: 673-678
Claussen, W. (2005), Proline as a measure of stress in tomato plants. Plant Science 168: 241-248
Cueto, C. A., Ebert, A. W., Rillo, E.P. and Orense, O.D. (1997) In vitro regeneration of coconut (Cocos nucifera L.) from immature inflorescences of tall cultivars. ISHS Acto Horticulturae 447: -
Dubois, M., Gilles, K.A., Hamilton, J. K., Rebers, P.A., and Smith, F. (1956). Colorimetric method for determination of sugars and related substances. Analytical Chemistry 28: 350-356.
Hare, P. D., Cress, W.A., and Staden, J. van., (1999). Proline synthesis and dehydration: a model system for elucidating stress-related signal transduction. Journal of Experimental Botany 50: 413-434
Hornung, R. and Verdeil J-L., (1999) Somatic embryogenesis in coconut from immature inflorescence explants In: Orapeza, C., Verdeil, J. L., Ashburner, G. R., Cardena, R. and Santamaria, J. M. (Eds), Current Advances in Coconut Biotechnology. Kluwer Academic Publishers, Dordrecht, The Netherlands, 297-309.
Ito A, Hayama H, Kashimura Y, (2002), Sugar metabolism in buds during flower bud formation; a comparison of two Japanese pear {Pyrus pyrifolia (Burm.) Nak} cultivars possesing different flowering habits. Scientia Horticulturae 96: 163-175.
Jackson, D.I. and Sweet, G.B. (1972), Flower initiation in temperate woody plants. Hort Abst. 42: 9-24
Olley, C.M., Joyce, D.C. and Irving, D.E., (1996) Changes in sugar, protein, respiration and ethylene in developing and harvested Geraldton waxflower (Chamelaucium uncinatum) flowers Newzealand Journal of crop and Horticultural Science 24: 143-150.
Ranwala, A.P. and Miller, W.B., (1998) Sucrose- cleaving enzymes and carbohydrate pools in Lilium longiflorum floral organs. Physiologia Plantarum 103: 541-550.
Rodrigues-Otubo, B. M., Penteado, M. I. de O. and Valle, C. B. do (2000) Embryo rescue of interspecific hybrids of Brachiaria spp. Plant Cell Tissue and Organ Culture 61(3): 175-182
Samaras, Y., Bressan, R.A., Csonka, L.N., Garcia-Rios, M.G., Paino, D., Urzo, M. and Rhodes, D. Proline accumulation during drought and salinity, In: Smirnoff N. (Ed.), Environment and Plant Metabolism, Bios Scientific Publishers, Oxford, 1995. 161-187
Verdeil, J.L., Huet, C., Grosdemange, F. and Buffard-Morel, J. (1994) Plant regeneration from cultured immature inflorescence of coconut (Cocos nucifera L.): evidence for somatic embryogenesis, Plant Cell Reports 13: 218-221
