Week 6 - Totipotency and Reproduction in Plant

This week we continue with last week topic, which is about the cell division in plant cell, mainly focusing on totipotency. There are four ways for an explants (for example, a piece of leaves) to form it’s shoots and roots :

i.                     Direct organogenesis – The explants will be differentiated directly to form its shoots and roots.

ii.                   Direct somatic embryogenesis –The explants will form an embryo, and the embryo will then developed into shoots and roots.

iii.                  Indirect organogenesis – The explants will form callus, a groups of undifferentiated cells and then it will develop to form organs such as roots or shoots

iv.                 Indirect somatic embryogenesis – The explants will first form callus, the callus then develop into an embryo, and then shoots and roots will be formed from the embryo.

This are the ways where tissue culture is carry out. In this topic I learn that it is very important to know the ratio or auxin and cytokinin in order to let the explants or callus to develop it shoots or roots. Auxin will be stimulating the growth of shoots, while cytokinin stimulates the growth of roots. The correct amount is needed to determine the degree of shoot and/or root formation in tissue culture. A high ratio of cytokinin to auxin favours shoot production, whereas a high auxin to cytokinin ratio favours root production. Intermediate levels of both hormones enhance callus formation. Besides that we should know that when the plants have undergoes tissue culture, we cannot transfer it immediately to exposure of sun. This is because during tissue culture, they had adapted to the environment where the humidity is high and the sun exposure is low. Directly bringing the tissue-cultured plant will causes the plant to be dehydrated and die. Moreover there are some factors that need to be considered when we are doing tissue culture, such as the air flow, fresh media and also sufficient food for the plant. No stress should be given to the plants, as stress will lead to the increase or hormone ethylene, excessive of this hormone will cause the retardation of growth. Next there are also factors need to be considered and decide when totipotency is carry out such as sources of explants, age of explants, the size of explants, energy sources, the season where the plant will grow and etc. However there are many successful cases for tissue culture, there is still a problem to tissue culture woody plant. Hence woody plant is known as recalcitrous.

Next, we study about reproduction in plant. There are 2 types of reproduction which are asexual (budding, rhizomes etc. ) and sexual. Sexual reproduction is the fusion of male and female gametes, where asexual doesn’t involves the fusion of gametes.

Sexual Reproduction

During embryogenesis, the zygote has suspensor which is important for the plant growth. Without it, it will not grow. There is four types of tissue culture, which are embryo culture, organ culture, callus culture and cell culture. If we use anther in culturing this plant we will get a haploid plant.

Embryogenesis of dicotyledon plant - where the heart at the heart stage is visible.

Beside the lecture, we discuss again about our Trainee Scientist, our topic is on transport mechanism in cell membrane. We are asked to prepare on our proposal, listing the learning outcomes, activities that we are doing and also questionnaire. The Trainee Scientist program basically is to gain interest of primary student on science subjects. In order to do that, we need to prepare interesting activities, hands on to involve them in it. Besides this is also to inspire them, to make them understand more about the fun of learning sciences, that science is really interesting.I really looking forward for this Trainee Scientist program, where I get the opportunity to inspire the younger generation, make them love science and they might be a successful scientist in the future.