51.
Match List-I with List-II and select the correct answer:
List-I (Diseases) List-II (Causative agents)
a. "Fire blight" of apple and pear 1. Pseudomonas solanacearum
b. "Crown gall" of tomato 2. Pseudomonas cirri
c. "Citrus canker" 3. Bacterium tumefaciens
d. "Brown rot" of Solanaceae 4. Bacillus amylovorus

52.
Consider the following statements and choose the correct answer:
1. The biogeographical realms are regions made up of whole continents, or of large parts of a continent, separated by major geographic barriers and characterized by the presence of certain unique animals and plants
2. In each biome the kind of climax vegetation is uniform - grasses, conifers, deciduous trees but the particular species of plant may vary in different parts of the biome
3. There is usually a sharp line of demarcation between adjacent biomes
4. The definition of biome includes not only the actual climax community of a region but also the several intermediate communities that precede the climax community

53.
Consider the following statements regarding the embryological features of Exocarpus and choose the correct answer:
1. The development of anther is normal
2. Four celled pollen grains are shed at the time of dehiscence of anther
3. Development of 8 nucleate Polygonum type of embryo sac takes place
4. The seed is not 'naked'

54.
Consider the following statements and choose the correct answer:
1. Control of land loss can be attempted through restoring forest and grass cover to check erosion and floods
2. Shifting cultivation can be replaced by crop rotation, mixed cropping or developing piantation crops which would improve fertility and support a large population
3. Salinity can be prevented by covering the area with appropriate plant species and by raising trees as wind breaks
4. Shifting sand can be controlled by mulching

57.
Consider the following statements regarding the Andaman and the Nicobar islands and choose the correct answer:
1. The islands have nearly 450 and 13.8 square miles of mangrove forests
2. This forest develops in areas covered by brackish water at high tide such as mud-flats along tidal streams
3. The dominant family in these islands is Acanthaceae
4. The mangrove forests are largely composed of single species or a few allied species

58.
In many temperate plants, subjecting them to very low temperatures for a short duration may result in rapid and more flowering when returned to normal temperature which is referred to as

59.
Match List-I with List-II and select the correct answer:
List-I List-II
a. Orthotropous ovule 1. The ovule is completely inverted in its orientation due to approximately 180° curvature of the funiculus
b. Anatropous ovule 2. The ovule is erect and is devoid of any curvature with the micropyle distal and directed away from the placenta
c. Hemianatropous ovule 3. The body of ovule is twisted only half way so that the degree of curvature is at right angle to the funicle
d. Campylotropous ovule 4. The body of ovule becomes curved so that the micropyle and chalaza come to lie on either side of the funicle