Plant growth regulators

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Plant Hormones and Plant Growth Regulators

Another factor in plant growth is the influence of plant hormones.  Hormones are chemicals produced by plants that regulate the growth processes.

Plant growth regulators are chemicals applied by a horticulturist to regulate plant growth.  In plant propagation, cuttings are dipped in a rooting hormone to stimulate root development.  In greenhouse production, many potted flowering plants may be treated with plant growth regulators to keep them short.  Seedless grapes are treated with plant growth regulators to increase the size of the fruit.  In special situations, turf may be treated to slow growth and mitigate the need for mowing.  

Plant Hormones

Different hormones affect different plant processes.  Understanding how hormones work allows horticulturists to manipulate plants for specific purposes. 

• Auxins produced in the terminal buds suppress the growth of side buds and stimulate root growth.  They also affect cell elongation (tropism), apical dominance, and fruit drop or retention.

• Gibberellins affect:


• The rate of cell division
• Flowering
• Increase in size of leaves and fruits
• Seed and bud dormancy
• Induction of growth at lower temperatures (used to green up lawns 2 to 3 weeks earlier)


• Cytokinins promote cell division, and influence cell differentiation and aging of leaves.


• Abscisic acid is considered the “stress” hormone.  It inhibits the effects of other hormones to reduce growth during times of plant stress.

Pollination and embryo development

A Look at Pollination

All living organisms have one major goal in common, which is to pass along their genetic information to the next generation by creating offspring. Flowering plants create seeds, which carry the genetic information of the parents and develop into a new plant. In order for seeds to be created, a process called pollination must occur.

Pollination is when pollen grains from an anther, the male portion of a flower, are transferred to a female part in the flower, known as the stigma. In order for pollination to be successful, the pollen grains transferred must be from a flower of the same species.

After the pollen grains land on the stigma, they create a pollen tube through the length of the style or stalk connecting the stigma and ovary. Once the pollen tube is complete, the pollen grain will send sperm cells from the grain down to the ovary. When the sperm cells reach the ovary and the egg cells, fertilization will occur, which will result in the formation of the seed. The seed will then be released from the parent plant and will be able to grow into a plant and continue the reproductive cycle using the method of pollination.

Zygotic embryogenesis in higher plants describes the developmental period in which the zygote undergoes a series of differentiation events, leading to the formation of a mature embryo. Establishment of the major embryonic organs and shoot and root apical meristems occur though partitioning events along the apical–basal axis, and many of these events are guided by the hormone auxin. Formation of the three embryonic tissue systems occurs along a radial axis perpendicular to the apical–basal axis. The mature zygotic embryo is generally developmentally arrested, metabolically quiescent and enclosed within maternal tissues of the seed. Somatic cells can be induced to divert from their normal fate and develop into embryos in a process termed somatic embryogenesis. Auxin and other plant hormones appear to play critical roles in inducing embryogenic competence. Zygotic and somatic embryogenesis represent parallel developmental programs in which cells acquire embryogenic cell fate and develop into mature embryos.

Somatic embryogenesis has been the method of choice for tissue culture, regeneration and transformation of maize for over twenty years. Somatic embryogenesis plays an important role in clone propagation. When integrated with conventional breeding programs and molecular and cell biology techniques, somatic embryogenesis provides a valuable tool to enhance the progress of commercial crop species.

Endosymbiosis and the Evolution of Eukaryotes

What is endosymbiosis?The topic that was brought before is about cell theory.But how do cell form?There are a few main point to explain how the cell form itself.

Endosymbiosis is the concept of one cell engulfing another and both cells benefiting from the relationship.

Endosymbiosis was originally considered after the observation of the similarity between plant chloroplasts and free-living cyanobacteria.

Endosymbionts may have transferred some of their DNA to the host nucleus, thus becoming dependent on the host for survival and completing full integration into a single organism.

The Endosymbiotic Hypothesis

The endosymbiotic hypothesis concerns the origin of mitochondria and chloroplasts, two organelles contained within various eukaryotic cells.  According to this hypothesis, these organelles originated as separate prokaryotic organisms that were taken inside a primordial eukaryotic cell.  Such symbiotic relationships in which two species are dependent upon one another to varying extents served as crucial elements of the evolutionary progression of eukaryotic cells. 

The Cell Theory

When Schleiden and Schwann proposed the cell theory in 1838, cell biology research was forever changed. The cell theory states that: All life forms are made from one or more cells. Cells only arise from pre-existing cells. The cell is the smallest form of life. The cell theory also provides us with an operational definition of "life." We will learn about prokaryotes, eukaryotes, and viruses.For now time being there are another 4 modern cell theory Modern Cell Theory -has additional 4 statements: the cell contains hereditary information which is passed on from cell to cell during cell division All cells are basically the same in chemical composition and metabolic activities All basic chemical and physiological functions are carried out inside the cells (movement, digestion,homeostasis etc.) Cell activities depends on the activities of subcellular structures within the cell (organelle, nucleus and plasma membrane)

From what I understood cell theory refers to the idea that cells are the basic unit of structure in every living things.. This theory is one of the foundations of biology. The theory says that new cells are formed from other existing cells, and that the cell is a fundamental unit of structure, function and organization in all living organisms.

Two types of cells

There is another basic cell structure that is present in many but not all living cells: the nucleus. The nucleus of a cell is a structure in the cytoplasm that is surrounded by a membrane (the nuclear membrane) and contains, and protects, most of the cell's DNA. Based on whether they have a nucleus, there are two basic types of cells: prokaryotic cells and eukaryotic cells.

Prokaryotic cells are cells without a nucleus. The DNA in prokaryotic cells is in the cytoplasm rather than enclosed within a nuclear membrane. Prokaryotic cells are found in single-celled organisms, such as bacteria. Organisms with prokaryotic cells are called prokaryotes. They were the first type of organisms to evolve and are still the most common organisms today.

Eukaryotes  are organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. The most characteristic membrane bound structure is the nucleus.. Animals, plants, fungi, and protists are eukaryotes.

Eukaryotic cells allow larger and more complex organisms to be made, and asingle eukaryotes cell complex than prokaryotic cells. Whether eukaryotic cells live singly or as part of a multicellular organism, their activities can be much more complex and diversified than prokaryotic. In prokaryotes, all internal cellular events take place within a single compartment, the cytoplasm. Eukaryotes contain many subcellular compartments called organelles. Even single-celled eukaryotes can display remarkable complexity of function; some have features as specialized and diverse as sensory bristles, mouth parts, muscle-like contractile bundles, or stinging darts.

The History of Life




A few weeks ago I learned about The History of  Life-how life begin.There are afew approaches or ways or ideas on how at first the life begin.First it is stated that an organic molecule is form as a product of inorganic molecule after go through all the natural phenomena on earth and the second one stated that organic molecule could be come from other planet through the comets ,asteroids.At first we must understand that an organism is made up of organic molecule.Organic molecule is the basic component of genetic materials.Back to the first ideas or theory it is really something provable as an experiment has been conducted known as Miller-Urey’s experiment (1953).Here I would like to say that the first idea is quite logic but not to say that the second idea is not acceptable.Yes of course it is proved by experiment that organic chemicals is produced from inorganic chemicals through out certain processes however it can be that organic chemicals come through comets and asteroids from other undiscoverable point of view.The natural was created by the super-natural. Creation is beyond human understanding and analysis. Truth has a certain ring..when you hear it, you just know. The more you study science, the more you believe in God, because the theory is never ever complete, there is always a missing part.

Theory of  evolution



Evolution is the changes of an organism through time.The idea of evolution first started by Aristotle.Aristotle said that organisms from simple to complex and moving to perfectness.Then the idea followed by Jean Baptiste Lamarck.Lammarck said that evolution occurred by the inheritance of acquired characteristics of an organism.He also said that an organism are subject to a force which moves them from simplicity to complexity by mean that organisms change to adapt to the enviroment.Before Charles Darwin theory there is another theory by Charles Lyell which stated that the earth is very old and a lot of natural process had happened until  what earth look like now..Charles Lyell theory leads to the most famous Charles Darwin theory which stated that evolutionary change comes through the production of variation where the process is called the natural selection .

1. Evolution: species come and go through time, while they exist they change.
2. Common descent: organisms are descended from one, or several common ancestors and have diversified from this original stock
3. Species multiply: the diversification of life involves populations of one species diverging until they become two separate species; this has probably occurred billions of times on earth!
4. Gradualism: evolutionary change occurs through incremental small changes within populations; new species are not created suddenly.
5. Natural selection: evolutionary change occurs through variation between individuals; some variants give the individual an extra survival probability.