Roles of lipids in coconut (Cocos nucifera L.) embryogenesis
File(s)
Author(s)
Lopez Villalobos, Arturo
Type
Thesis
Abstract
The coconut palm (Cocos nucifera L.) is an important crop world-wide but to maintain
its status, a method of somatic embryogenesis to produce clonal populations is required.
Despite recent improvements in callus production the formation of somatic embryos and
plantlet regeneration remain problematic.
This thesis identified lauric acid accumulation as a potential marker for coconut
seedling development and used it as a nutrient in combination with other culture
conditions to promote embryogenesis or germination. It was found that lauric acid
content was correlated with seedling development. The fatty acid together with
naphthaleneacetic acid, 6-benzylaminopurine and 77Z}'o-inositol in the culture medium
increased the growth of the organs (shoots, roots and haustorium) of seedlings
mimicking, to some extent, the development of intact nuts. Metabolic studies showed
that lauric acid is used as a precursor of other fatty acids and complex lipids and that
their contents varied with the organ and the developmental stage of the seedling. In
somatic embryogenesis, lauric acid combined with ABA promoted callus differentiation
and formation of proembryos.
Studies of 2,4-D metabolism revealed that deciding upon the optimum concentration of
the auxin to use in coconut somatic embryogenesis is complicated by its rate of
metabolism and conditions of culture (sucrose and 2,4-D concentrations). Five classes
of metabolites (glucose esters, peptide conjugates, basic metabolites, triacylglycerol
analogues containing short-chain elongated forms of 2,4-D and triacylglycerol
analogues containing long-chain elongated forms of 2,4-D) were formed in the explants
and their proportions varied according to the growth of the cultured tissue. The presence
of non-polar metabolites was associated with de-differentiation of cxplants.
Finally an improved protocol for somatic embryogenesis is suggested but many details
remain to be improved.
its status, a method of somatic embryogenesis to produce clonal populations is required.
Despite recent improvements in callus production the formation of somatic embryos and
plantlet regeneration remain problematic.
This thesis identified lauric acid accumulation as a potential marker for coconut
seedling development and used it as a nutrient in combination with other culture
conditions to promote embryogenesis or germination. It was found that lauric acid
content was correlated with seedling development. The fatty acid together with
naphthaleneacetic acid, 6-benzylaminopurine and 77Z}'o-inositol in the culture medium
increased the growth of the organs (shoots, roots and haustorium) of seedlings
mimicking, to some extent, the development of intact nuts. Metabolic studies showed
that lauric acid is used as a precursor of other fatty acids and complex lipids and that
their contents varied with the organ and the developmental stage of the seedling. In
somatic embryogenesis, lauric acid combined with ABA promoted callus differentiation
and formation of proembryos.
Studies of 2,4-D metabolism revealed that deciding upon the optimum concentration of
the auxin to use in coconut somatic embryogenesis is complicated by its rate of
metabolism and conditions of culture (sucrose and 2,4-D concentrations). Five classes
of metabolites (glucose esters, peptide conjugates, basic metabolites, triacylglycerol
analogues containing short-chain elongated forms of 2,4-D and triacylglycerol
analogues containing long-chain elongated forms of 2,4-D) were formed in the explants
and their proportions varied according to the growth of the cultured tissue. The presence
of non-polar metabolites was associated with de-differentiation of cxplants.
Finally an improved protocol for somatic embryogenesis is suggested but many details
remain to be improved.
Version
Open Access
Date Issued
2002-08
Date Awarded
2002
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Hornung, Roland
Dodds, Peter
Sponsor
Consejo Nacional de Ciencia y Tecnología (Mexico)
Publisher Department
Agricultural Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)
Author Permission
Permission granted