References:

• Plant cell biology - Google Books http://books.google.ie/books?id=zhbtZbWTEt8C&lpg=PA479&dq=seed%20germination%20and%20amylase&pg=PA479#v=onepage&q=seed%20germination%20and%20amylase&f=false
• http://www.google.ie/images?hl=en&source=hp&biw=1066&bih=590&q=seed+germination+and+amylase&btnG=Search+Images&gbv=2&aq=f&aqi=&aql=&oq=
• http://books.google.ie/books?id=hSYBjgwbjY4C&lpg=PA215&dq=seed%20germination%20and%20amylase&pg=PA215#v=onepage&q=seed%20germination%20and%20amylase&f=false
• Salisbury, Frank B. & Ross, Cleon W. 1992. Plant Physiology. Volume 1. Wadsworth Pub. Co., 1992. University of California. Page 329-382.
• Popper. Zoe. 2011. Aquatic Plant science II: Laboratory handout. Experiment 5. Pages 27-29 & Page 33.

Discussion:

During cereal seed germination, active GAs induce de-novo synthesis of α-amylase RNA. The GAs stimulate the aleurone cells to transcribe the hydrolytic enzyme α-amylase, in the aleurone layer of the cereal seed.  The aleurone layer secretes α-amylase and other hydrolytic enzymes such as protease, ribonuclease, β-amylase, and α-1,3-glucanase. α-amylase plays an important role in hydrolysis of stored starch in the endosperm, converting it to simple sugars such as glucose, which provide the energy for development of shoots and roots. Many other enzymes that hydrolyse lipids and proteins are also produced in the aleurone layer. Sugars and amino acids are released into the scutellum, where they are absorbed by the embryo, providing nourishment for it to develop into a seedling. It is apparent that the growth regulating hormone Gibberellin is vital for the stimulation of seed germination, resulting in shoot and root emergence from the seed coat. 

Role of GAs in seed germination.

Results:

• The seeds are removed from the petri dishes.
• A dark yellow-brown aqueous iodine solution is poured over the agar plates. Iodine solution is used to test whether starch hydrolysis has occurred. A colourless 'halo' around the seed halves indicates starch hydrolysis. Where starch is present, the iodine solution will turn from yellow-brown to blue-black.
• The skimmed milk plates are flooded with biuret reagent and left for 2 minutes.
• Biuret reagent is used to detect peptide bonds, following hydrolysis of protein molecules. A positive result for proteolytic hydrolysis occurs when the reagent changes from blue to violet. 
• The results of these treatments show that upon germination, the embryo begins to produce amylase and proteolytic enzymes.
• The boiled seeds, which act as a control, are unable to synthesise proteins, as they are dead.

Iodine test.

Biuret test.

                                  

Investigation of enzyme activity during seed germination: Methodology.

Broad bean seeds showong cotyledons.

• The germination process was accomplished in the laboratory by soaking half-broad bean ( Vicia faba ) seeds in starch and milk agar present in two petri dishes.
• A control was used, to compare the findings. This was achieved by boiling the barley seeds before putting them into the petri dish soaked with water.
• Four barley seeds are split in half, seperating the cotyledons.
• Two of the split seeds are killed by boiling, for 5 minutes. These are used as the controls.
• All the seeds are sterilised for ten minutes, by soaking in disinfectant solution.
•  The petri dishes are labelled so as to avoid confusion eg 'Raw and Boiled seeds.'
• The seed halves are placed face down, in the appropriate petri dishes containing filter paper which have been saturated with either starch or milk agar.
• The plates are incubated at room temperature ( 18-20 degrees celcius) for 48hours.
• The results were analysed.

Petri dishes with filter paper.

Introduction.

Molecular structure of Gibberellin (GA).

Gibberellins, a group of plant growth hormones, are synthesised in high concentrations in developing seeds. They are also synthesised in varying amounts in other parts of the plant eg apical shoot buds and root tips. One particular and important function of gibberellins is there role in stimulating hydrolysis and transport of stored macromolecules, to the developing embryo. Following water uptake, in the initiation of germination, gibberellin diffuses to a specialised layer of cells, called the aleurone layer. In response to gibberellin, these cells which are rich in protein, produce and release enzymes that hydrolyse lipids, starch and proteins in the  endosperm. The starch, lipids and proteins are converted to sugars, fatty acids and amino acids, respectively. The embryo will use these for growth and development.

In this experiment carried out on germinating barley seeds, the results showed that the release of gibberellin from the embryo, triggers the synthesis of the hydrolytic enzyme alpha-amylase, which digests starch in the endosperm. It is hypothesised that gibberellins, in this instance atleast, turn on the genes encoding for alpha-amylase.