What postulates that the state and activity of a particular region of chromatin depends upon the specific modifications, or combinations of modifications, to the histone tails in that region? It suggests that the pattern of modifications adorning the tails of the core histones contains encoded information governing the properties of the nucleosomes containing them. the DaVinci code the chemiosmotic hypothesis the histone code the genetic code Solution Answer is the histone code. Modifications to the histone proteins which bind to the dna, make the fragment of dna accessible to various enzymes..

1. What process causes plant ion-uptake to acidify soil? What soil pH range generally promotes the
greatest availability of cations?
Solution
The process that causes plant ion-uptake to acidify soil is known as soil acidification. It is a
process by which the soil pH decreases over time without producing any visible signs. Slow soil
acidification occurs under natural conditions over thousands of years, with high rainfall areas
most affected, whereas, rapid acidification occurs over a few years under intensive agricultural
practices. Soil acidification affects the surface and the subsoil simultaneously. However, areas
that remain unaffected by industrial pollution, there soil acidification is mainly caused by the
release of protons (H+) during the oxidation of carbon (C), sulphur (S) and nitrogen (N)
compounds in soils. During nitrogen cycling, the major processes leading to acidification
consists of the cation imbalance over anion during uptake in the rhizosphere of plants, during
nitrification from fixation or from the fertilizers, and during the removal of plant and animal
products by leaching. The uptake of excess cations over anions by plants results in the
acidification of the rhizosphere which is a “localized” effect and can be balanced by the release
of hydroxyl (OH-) ions during subsequent plant decomposition.
Soils are considered acidic below a pH of 5, and alkaline above a pH of 7.5 and very alkaline
above a pH of 8. It has been observed that the “ideal” soil pH is close to neutral, which fall
within a range from a slightly acidic pH of 6.5 to slightly alkaline pH of 7.5. It has been
determined that most plant nutrients are optimally available to plants within this range helpful for
plant root growth. However, Nitrogen (N), Potassium (K), and Sulfur (S) are major plant
nutrients that enhance plant growth and development. Most of the plant nutrients (cations) tend
to be less available when soil pH is above 7.5, and are optimally available at a slightly acidic pH
in the range of 6.5 to 6.8.