- I'm working on somatic embryogenesis of Polianthes tuberosa L. (Agavaceae). In a publication it has been reported that heart-shaped, torpedo-shaped and cotyledonary stages were observed during somatic embryogenesis of Polianthes tuberosa. To the best of my knowledge these stages are occurred during somatic embryogenesis of dicots. Embryo development in monocots includes proembryo, globular, scutellar, and coleoptilar stages.
- 1. Are there any exceptions to these pathways of embryogenesis?
- 2. Are these pathways different between zygotic and somatic embryogenesis?
In date palm, which is a monoct, the stages of somatic embry ogensis are pre-globular, globular. bipolare and cotyledonary shaped. the difference between zygotic and somatic embryogensis, is that somatic embryogenesis gives rise to plant-let, while the zygotic embryo gives rise to seed.
As explained Abbas, in dare palm size of embryos is very large and structures are clearly visible. But in several other monocots like cereals and liliaceae, size of developing structures is very small and it will depend upon the experience and expertise of researcher to observe them, at right time and at right developing stage. If you miss to observe the cultures for 1-2 days, you may miss the stage. The stages may not be exactly same as dicots.
Dear Professor Abbas and Professor Ramawat,
Thank you very much for your comments.
For example, can we see heart-shaped stage in a monocot plant such as date palm or tuberose?
Please, read the attached paper on date palm.it shows you,heart -shaped stage, etc.
Dear Ali,
Basically heart shape leads to two cotyledons which are absent in monocots. Therefore, it is not possible to see a clear shape. Generally it is elongated.
Thanks for attached file.
Figures of this article are of poor quality. All stages show some globular bodies that look alike and there is no distinct trend. Moreover, there is no histological evidence. In fact, according to Hartmann and Kester’s plant propagation: principles and practice (2011), heart-shaped stage does not occur during monocots embryogenesis.
Dear Professor Ramawat,
I agree with you. However, authors of this article have claimed that "By viewing cv. Khanizi under a binocular microscope we observed different stages of embryogenic callus: globular, heart, torpedo and cotyledonary stage (Ramawat, 2003) (Figure 1a-d)."
I cannot accept this claim.
Dear Dr Ali
As I know that the somatic embryogenesis in monocot is a bit different than dicots. The earlier stages are similar up to globular stage (one can also see somthing like early hear shape stage. From this stage (early heart shape) in monocot embryo only one cotyleden grow and normally you donot see torpedo and cotyledeonary stages. However, cultures can behave differently and any abnormality could be seen depending upon the concentration of plant growth regulators (PGRs). Especially when high concentration of auxin is present, this could lead to development of additional cotyledons. Here I refer to an article of Liu et al (1993; In the special issue of The Plant Cell), where it was clearly established that such things can happen in culture, which is due to passive diffusion of auxin. In the absence of exogenous auxin in medium the monocot embryogenesis proceed in a normal way (like typical monocot embryogenesis), an example of the same you can seen in our article on glasiolus "Kumar A, Sood A, Palni LMS, Gupta AK (1999) In vitro propagation of Gladiolus hybridus Hort. Synergistic effect of heat shock and sucrose on morphogenesis. Plant Cell, Tissue & Organ Culture 57:105-112." I hope this will serve your query.
Regards
Anil Kumar
The monocot somatic embryos lack the hart shape seen in dicot somatic enbryos. Other stages are seen in both. www.msu.edu/~stickle1
Dear Dr. Anil Kumar,
Thank you very much for your comprehensive answer.
Dear Professor Mariam Sticklen,
It's my pleasure to see your helpful answer.
In angiosperms development stages during somatic embryogenesis are: globular, heart, scutellar and coleoptilar
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