Leghaemoglobin protein

Leghaemoglobin protein- In case of nitrogen-fixing root nodules of leguminous plants which belongs to family fabaceae nodule formation takes place.

Nodules contain an oxygen binding heme protein called leg-haemoglobin . 

Location -This protein is present in cytoplasm of infected nodule cells at high concentration (700uM). 

It gives the nodule a pink colour apperance. The host plant produces the globin portion of the leg haemoglobin in response to infection by rhizobia bacteria. The bacterial symbiont produces the heme portion. 

Properties-

• Leg haemoglobin has a high affinity for oxygen about 10 times higher than B-chain of human haemoglobin.

• It stores enough oxygen to support nodule respiration for a few seconds.

• Leghemoglobin buffers the concentration of free oxygen in the cytoplasm of infected plant cells to ensure the proper function of root nodules.

                                Image source-http://biology4isc.weebly.com/3-mineral-nutrition.html

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Hydropathy index

Hydropathy index-  

It is related to amino acids. It represents the hydrophobic properties of amino acid side chains.The larger the number in the scale the more hydrophobic the amino acid .

HYDROPATHY SCALES (a measure of hydrophobicity) -- a way of quantitating whether a 20 amino acid segment might be hydrophobic enough to be a transmembrane helix. More hydropathy index means more energy is required to stabilize in the aquous environment .

• More + numbers indicate more hydrophobic R groups;
•  more - numbers indicate more hydrophilic R groups.

The free energy change accompanying movement of amino acid side chain from hydrphobic solvent into water .

Charged (polar )-Exergonic Aromatic and Aliphatic-Endergonic 

Hydropathy plots (plot of hydropathy index vs. residue number where the residue number is actually the average hydropathy value for a "sliding window" of, say, 7 residues, moving down the protein from N to C-terminus -- for example, average values for residues 1-7, then for 2-8, then 3-9, etc. are plotted.

• Depends on the hydropathy scale being used (i.e., what nonpolar solvent was used for the partitioning experiments to determine relative solubilities in H₂O vs. nonpolar solvent); zero is always the midpoint of being neither hydrophilic or hydrophobic, and negative values are more hydrophilic, while positive values are more hydrophobic.

                                           Image source credit- http://slideplayer.com/slide/7360690/

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Radial micellation

Stomata- Openings of plant leaves particularly found in lower epidermis

surrounded by a pair of highly specialized cells called guard cells.  Guard cell  has a cell wall, chloroplasts, nucleus, mitochondria, endoplasmic reticulum, golgi apparatus, ribosomes and lack a plasmodesmata (cytoplasmic connections).  

 Cell walls of guard cells are unique in being unevenly thickened and having radial micellation of microfibrils. The region of cell wall that lines the periphery of the pore is thicker than the rest.when guard cells become turgid, the thicker region of the cell wall cannot stretch lengthways and, hence bends opening the pore. Inside the leaf, beneath the stomatal pore and guard cells there is a substomatal cavity. This cavity is filled with water vapor formed due to evaporation of water from cell walls of the cells lining it.

Radially micellated guard cell

Image source credit-http://hubpages.com/education/The-Crucial-Role-of-Stomata-in-Plant-Transpiration-and-Photosynthesis



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