Insights Secure PRELIMS – 05 August 2014

Vernalisation

Vernalization is the acquisition of a plant’s ability to flower in the spring by exposure to the prolonged cold of winter, or by an artificial equivalent. After vernalization, plants have acquired the ability to flower, but they may require additional seasonal cues or weeks of growth before they will actually flower.

Many plants grown in temperate climates require vernalization and must experience a period of low winter temperature to initiate or accelerate the flowering process. This ensures that reproductive development and seed production occurs in spring and summer, rather than in autumn. The needed cold is often expressed in chill hours. Typical vernalization temperatures are between 5 and 10 degrees Celsius (40 and 50 degrees Fahrenheit

Caspian Sea

60 years

39, 29 and 11 respectively

The employed members of Mohan’s family are honest

I  and IV

A’s son

C and E

Kaivalya

http://en.wikipedia.org/wiki/Kevala_Jnana

56.25 km per hour

The valleys are cooler than the ridges

Portugese

II and III

None in the group

The size of the shadow of the moon on the earth is small compared to the cross section of the earth

If the Moon were in a perfectly circular orbit, a little closer to the Earth, and in the same orbital plane, there would be total solar eclipses every single month. However, the Moon’s orbit is inclined (tilted) at more than 5 degrees to Earth’s orbit around the Sun (see ecliptic) so its shadow at new moon usually misses Earth. Earth’s orbit is called the ecliptic plane as the Moon’s orbit must cross this plane in order for an eclipse (both solar as well as lunar) to occur. In addition, the Moon’s actual orbit is elliptical, often taking it far enough away from Earth that its apparent size is not large enough to block the Sun totally. The orbital planes cross each year at a line of nodes resulting in at least two, and up to five, solar eclipses occurring each year; no more than two of which can be total eclipses.^[1][2] However, total solar eclipses are rare at any particular location because totality exists only along a narrow path on Earth’s surface traced by the Moon’s shadow or umbra.

Multiple reflection and interference

The iridescent colours of a soap film are caused by interfering of (internally and externally) reflected light waves, a process called thin film interference and are determined by the thickness of the film. This phenomenon is not the same as the origin of rainbow colours (caused by the refraction of internally reflected light), but rather is the same as the phenomenon causing the colours in an oil slick on a wet road.

http://www.animations.physics.unsw.edu.au/jw/light/soap-bubbles.htm

A is true but R is false

http://chemistry.about.com/od/howthingsworkfaqs/f/how-does-salt-melt-ice.htm

If there is high temperature during the time of ripening

Growth is closely related to temperature. Optimum temperature for sprouting (germination) of stem cuttings is 32° to 38°c. It slows down below 25°, reaches plateau between 30°-34°, is reduced above 35° and practically stops when the temperature is above 38°.Temperatures above 38° reduce the rate of photosynthesis and increase respiration. For ripening, however, relatively low temperatures in the range of 12° to 14° are desirable, since this has a noticeable influence on the reduction of vegetative growth rate and enrichment of sucrose in the cane.
At higher temperatures reversion of sucrose into fructose and glucose may occur besides enhancement of photorespiration thus leading to less accumulation of sugars. Severe cold weather inhibits bud sprouting in ratoon crop and arrests cane growth. Temperatures lower than 0°C induces freezing of less protected parts such as young leaves and lateral buds. The damage depends upon the length of the cold period. Smut initiation and spread is high at ambient temperatures of 25° -30°. Similarly the spread of red not disease is high at higher temperatures (37°-400°) when all other conditions are similar. Rust incidence is high when the minimum temperatures are drastically reduced. Shoot-fly incidence is high in summer when the air temperatures are very high. Also higher shoot fly incidence was observed when the difference between maximum (day) and minimum (night) temperature are low.

1.8 m

6.5 to 7

The first order of business is a quick review of pH and the associated terminology. Soil pH or soil reaction is an indication of the acidity or alkalinity of soil and is measured in pH units. The pH scale goes from 0 to 14 with pH 7 as the neutral point. As the amount of hydrogen ions in the soil increases, the soil pH decreases, thus becoming more acidic. From pH 7 to 0, the soil is increasingly more acidic, and from pH 7 to 14, the soil is increasingly more alkaline or basic.

Using a strict chemical definition, pH is the negative log of hydrogen (H⁺ ) activity in an aqueous solution. The point to remember from the chemical definition is that pH values are reported on a negative log scale. So, a 1 unit change in the pH value signifies a 10-fold change in the actual activity of H⁺, and the activity increases as the pH value decreases.

To put this into perspective, a soil pH of 6 has 10 times more hydrogen ions than a soil with a pH of 7, and a soil with a pH of 5 has 100 times more hydrogen ions than a soil with a pH of 7. Activity increases as the pH value decreases.

Agronomists generally use soil pH as measured in a 2:1 water-to-soil mixture as an index of a soil’s acidity or alkalinity. In a soil test report, pH is often reported with descriptive modifier as shown in Table 1.

Table 1. Soil pH and Interpretation
5.0	5.5	6.0	6.5	7.0	7.5	8.0
Strongly Acid	Medium Acid	Slightly Acid	Neutral	Neutral	Mildly Alkaline	Moderately Alkaline
			Best Range for Most Crops