Question

1. Name the closest relatives to the land plants.

2. List advantages and problems faced by early plants when they started colonizing terrestrial habitats.

3. List all the similarities that all current land plants share with charophytes. What distinguishes modern plants from charophytes?

4. Plants can be classified based on the presence or absence of___________________. Nonvascular plants are called……

5. Which form dominates the nonvascular plant life cycle? Which form is dominant for vascular plants?

6. Which additional characteristics are specific for vascular plants?

7. Describe life cycles of nonvascular and seedless vascular plants. Specifically, differentiate gametophytes in each group. How does fertilization occur in each case? Which structure produces and disperses spores in each case?

8. Describe the differences between seedless and seed producing vascular plants. What is pollen? Where are gametangia located? What does it mean heterosporous?

9. How Gymnosperms and Angiosperms differ from each other?

10. What is the composition of seeds?

11. Which other adaptations seed plants have? Describe the life cycle of Gymnosperms and Angiosperms.

12. What is the function of lowers? What is the origin of different parts of the flowers?

13. What are fruits? What is their contribution to the fitness of angiosperms?

14. List differences between monocots and eudicots.

15. What is etiolation? What happens during de-etiolation? In general what happens during signal transduction (describe each step)?

16. What causes the coleoptile to bend towards light? Where is the signal produced? Which part of the coleoptile is affected? Plant cells are surrounded by cells walls. How can they elongate? Describe the acid growth hypothesis.

17. List an example of a plant hormone that can exert different effects depending on concentration.

18 What are cytokinins doing?

19. What is the role of gibberellins?

20. Which molecule is responsible for ripening of the fruits and abscission of leaves?

21. To which hormones are brassinosteroids similar?

22. What are major roles of abscisic acid?

23. How can mechanical stress change plants morphology?

24. Phytochromes exist in active and inactive form. How is light influencing these forms?

25. When short-day plants are flowering? How about long-day pants?

26. Cyclic changes (for example opening of flowers) observed in plants during 24h period are called…

27. What is meant by stress for plants? How plants cope with stress? List abiotic factors affecting plants and means by which plants cope with them.

28. List defense methods used by plants against pathogens. What is the role of salicylic acid?

Answer 1

9. Class Gymnospermae (Cycads Conifers, and Ginkgos) Class Angiospermae(flowering plants)

1. No vessels in xylem, only tracheids(except Gnetales) no companion cells in phloem.

1. Xylem has vessels, phloem contains companion cells

2. Usually have cones on which sporangia and spores develop.

2. Produce flowers in which sporangia and spores develop

3. Seeds are naked that is the seeds are exposed; they are not enclosed in ovary.

3. Seeds are enclosed in ovary. 4. No fruit because no ovary

4. After fertilization ovary develops into fruit.

10. The gram seeds are brown in colour. They are pointed at one end and round at the other end. These are contained in a small fruit called, the pod. The gram pod is two or three-seeded. The seeds are attached to the wall of the pod by a stalk called the funiculus. When the mature seed is detached, the funiculus leaves a scar on the seed called the hilum. Just blow the hilum lies the micropyle in the form of a small pore. Water is absorbed through the micropyle during the germination of seed. If the soaked seed is squeezed, water is seen to ooze out of the micropyle. The seed is covered by the tough seed coat. The seed coat consists of two layers, outer brownish testa and the papery white membranous tegmen. The function of seed coat is protective. It protects the seed from desiccation, mechanical injury and extremes of temperature. It also protects the seed from the attack of bacteria, fungi and insects. On removing the seed coat, two massive and fleshy cotyledons are seen. The two cotyledons are attached laterally to the embryonal axis. The embryonal axis projects beyond the cotyledons on either side. The lower pointed end of the axis is the radicle which represents the embryonic or rudimentary root. The other end is feathery. It is called the plumule. It represents the first apical bud of the future plant and develops into the shoot. The plumule is seen only after separating the two cotyledons. The portion of the axis between radicle and the point of attachment of the cotyledons to the axis is called the hypocotyl and the portion between the plumule and the cotyledons is the epicotyl. The axis along with the cotyledon constitute the embryo.

11. Gymnosperms have the ovule/seed borne externally to all. Pollination is direct. The pollen grains possess a prothallus of two or more cells, one of which produces two non-motile or rarely motile male gametes. The embryo sac contains a tissue before fertilization which is known as rudimentatry prothallium and two or more archegonia. The haploid tissue of the female gametophyte itself is the endosperm of the seed. The seed habit is based on heterospory. It involves the retention of megaspore and female gametophyte within the ovule of the parent sporophyte until the embryo is well established.

An angiosperm starts its life cycle with the germination of the embryo contained in the seed. Within the frontiers determined by the species, the seedling grows into a plant that lives for a variable period of time but always goes through an early vegetative phase and later a reproductive phase either only once or several times. During the vegetative phase the plnat puts forth roots, stems and leaves and during the reproducitve phase, flowers and subsequently fruits and seeds.

12. the flower is a modified shoot, is only a figurative expression, and implies that the floral leaves are vegetative leaves and transformed to do a different function of reproduction, in the place of the ordinary function of photosynthesis.

When several flowers arise in a cluster on a common axis, the structure is referred to as an inflorescence. The common axis is the inflorescence axis which is also called rachis or peduncle. Several single flowers are attached to the inflorescence axis. In case of plants possessing underground rhizomes, the rachis or peduncle arises directly from the rhizome. Such a rachis is referred to as scape. In the case of lotus, the scape gives rise to a solitary flower. In plants like onion, the scape gives rise to an inflorescence.

13. The fruit may be defined as a fertilized and developed ovary. Fruits and seeds develop from flowers after completion of two processes namely pollination and fertilization. After fertilization, the ovary develops into fruit. The ovary wall develops into the fruit wall called pericarp and the ovules inside the ovary develop into seeds. The branch of horticulture that deals with study of fruits and their cultivation is called pomology.

14. Dicotyledon and Monocotyledon Seeds On the basis of number of cotyledons in the seed, angiosperms have been divided into two groups: 1. Monocotyledons having embryo with one cotyledon only, eg. maize, rice, wheat and onion. 2. Dicotyledons having embryo with two cotyledons, eg. pea, gram, bean and castor.

18. Physiological effects of cytokinin: The most important function of cytokinin is the promotion of cell division. In association with IAA, cytokinin initiates bud and root formation in callus tissue. External application of cytokinin promotes the growth of lateral buds even if the apical bud is intact. Cytokinin breaks the dormancy of many seeds and also promotes germination. Application of cytokinin delays the process of ageing in plants. This is also known as Richmond Lang effect.

19. Physiological effects of gibberellin m Gibberellins produce extraordinary elongation of stem. The elongation of stem is caused by the cell division and cell elongation induced by gibberellic acid. One of the most striking effects of the gibberellins is the reversal of dwarfism in many genetically dwarf plants. For e.g. ‘Rosette’ plant of sugar beet, when treated with GA undergoes marked longitudinal growth of axis attaining the normal size. m Rosette plants usually show reduced internodal growth. These plants exhibit excessive internodal growth when they are treated with gibberellin. This sudden elongation of stem followed by flowering is called bolting. Many biennials usually flower during the second year of their growth. For flowering to take place, these plants should be exposed to cold season. Such plants could be made to flower without exposure to cold season in the first year itself, when they are treated with gibberellins. Formation of seedless fruits without fertilization can also be induced by gibberellin treatment in many plants. eg. Tomatoes, apples, cucumbers, etc., Some of the light sensitive seeds can germinate by the treatment of gibberellic acid even in complete darkness. eg. barley, Gibberellin breaks dormancy in potato tubers.

22. Physiological effects of abscisic acid m Abscisic acid acts as growth inhibitor and induces bud dormancy in a variety of plants. ABA is a powerful growth inhibitor. It causes 50 per cent inhibition of growth of oat seedlings. As the name suggests abscisic acid is an hormone that stimulates abscission. ABA controls geotropic responses of roots. It stimulates positive geotropism in roots. Abscisic acid causes closure of stomata.

24. Phytochromes and flowering In 1959, Butler et al. were able to discover a photoreceptor flower inducing pigment in plants which they name phytochromes. It is believed to be widely present in all green plants. Chemically, phytochrome is a biliprotein and exists in two forms. One form absorbs red with the wave length of 660 nm called Pr and the other form absorbs far red with the wave length of 730 nm called Pfr. The two forms of phytochrome are interconvertible as shown below: Based on the absorption spectra, Pr is also called P 660 and Pfr is P 730. In short day plants, Pr promotes flowering while Pfr suppresses it , while it is viceversa in long day plants.

25. Plants are classified into three classes 1. The plants requiring longer exposure to light than their critical period are known as long day plants eg. wheat and oats. 2. The plants requiring light for a shorter period than their critical period are known as short day plants eg. tobacco and Chrysanthemum. 3. The plants in which flowering is unaffected by the photoperiod are known as day neutral plants eg. sunflower and maize.