Most dicots, such as Arabidopsis, seed development
follows two distinct phases and the embryo grows to full size and
replaces most of the endosperm at maturity. During the first
phase, the syncytial phase, a rapid growth and proliferation of the
endosperm occurs, which generates a large multinucleate cell and
results in a larger embryo sac or seed cavity . This
syncytium is then partitioned into individual cells by a specific type
of cytokinesis called cellularization .During the second phase,
embryo growth takes place at the expense of the endosperm. Upon
maturity, the seed contains only a single layer of endosperm cells
inArabidopsis.But in some dicot plant seeds,like coster bean,the endosperm still retained at maturity. What is the difference between these two kind of plant during the seed development? is there a key gene control the different development process？
Most eudicots embryos consume the endosperm but there are exceptions like castor bean. Most monocot seeds contain endosperm. When the endosperm is present, in both eudicot and monocot seeds, the cotyledon(s) is/are thin and function in mobilizing and transferring the nutrients from the endosperm to the seedlings after germination. I do not see it as a disadvantage or delayed developmental event as stated in the previous comment. We need to take into consideration the type of germination in each case. Most eudicots have an epigeal germination and the cotyledons become photosynthetic, so in a way it makes sense for the endosperm reserves to be transferred and stored in cotyledons. Most monocots have a hypogeal germination during which the nutrient reserves in the endosperm are directly used by the seedling via the cotyledon which remains in the seed underground.
Interesting question.
As you said, in most dicots the endosperm is 'consumed' during embryo development phase. This process is considered advanced because the endosperm is a separate entity as it is formed by fertilization of polar nuclei by the second sperm nucleus. On the other hand, cotyledons are an integral part of embryo, formed as a result of fertilization of the egg cell. In castor, the 'consumption' of the endosperm happens during germination and the cotyledons which were papery in the seed grow out into food reserves of the germinating seed. Please see link below:
https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcSnOfvSytiuH51_UJsLdJ-KRxlfZFhGAIBvlo6mbuLDLs9j3JnP0w
So, my guess is, genes controlling transfer of reserves to cotyledons during seed maturation of 'normal dicots' are expressed only during germination in castor. This is a delayed developmental event and I think this has a disadvantage, an energy consuming two step process as far as storage reserve mobilisation is concerned.
Most eudicots embryos consume the endosperm but there are exceptions like castor bean. Most monocot seeds contain endosperm. When the endosperm is present, in both eudicot and monocot seeds, the cotyledon(s) is/are thin and function in mobilizing and transferring the nutrients from the endosperm to the seedlings after germination. I do not see it as a disadvantage or delayed developmental event as stated in the previous comment. We need to take into consideration the type of germination in each case. Most eudicots have an epigeal germination and the cotyledons become photosynthetic, so in a way it makes sense for the endosperm reserves to be transferred and stored in cotyledons. Most monocots have a hypogeal germination during which the nutrient reserves in the endosperm are directly used by the seedling via the cotyledon which remains in the seed underground.
- Badges
- Science topic
- Similar topics
- Biological Science
- Botany
- Plant Biology