1. List the changes observed in angiosperm flower subsequent to pollination and fertilization.
A: Flower is the reproductive shoot which possesses androecium and gynoecium to produce
male and female gametes respectively. Depending on the type of plant species self or cross pollination takes place to transfer the pollen with male gametes to the stigma.
The pollination is followed by pollen tube entry into the ovule and embryosac and fertilization
of the male gamete with the egg cell in the embryosac. The changes that occur in a flower after fertilization are :
The calyx and corolla wither and fall off (Sometimes the calyx may be persistant)
Ex: Tridax, Brinjal
The stamens fall off.
The style and stigma fall off.
The ovary transforms into a fruit.
The ovules transform into seeds.
Zygote and endosperm are formed in the seed.
2. List three strategies that a bisexual chasmogamous flower can evolve to prevent self pollination (Autogamy).
A: Bisexual chasmogamous flowers prevent self pollination by the following out breeding devices:
a) Dichogamy: Maturation of androecium and gynoecium at different times in a flower is called Dichogamy. If the pollen is released before the stigma becomes receptive it is called Protandry.
Ex: Sunflower. If the stigma becomes receptive before the release of pollen it is called Protogyny. Ex: Datura.
b) Herkogamy: If the anthers and stigma are placed at different positions so that the pollen cannot come in stigma of the same flower it is called Herkogamy.
Ex: Gloriosa and Hibiscus.
c) Heterostyly: The styles of the flowers of the same species are in different heights.
d) Self-sterility: The germination of self-pollen on the stigma is prevented. Ex: Abutilon.
3. Discuss the various types of pollen tube entry into ovule with the help of diagrams.
A: Pollen grains germinate on the stigma of the flower and produce pollen tube which carries male gametes towards the ovule and embryosac. The pollen tube is formed by the intine of the ovule and emerges through the pores in the exine and grows down into the style. Later it enters the ovule by any of the following methods:
Porogamy: The pollen tube enters the ovule through the micropyle.
Mesogamy: The pollen tube enters the ovule through the integuments.
Chalazogamy: The pollen tube enters the ovule through the chalaza.
4. What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
A: During fertilization in angiosperms one male gamete fuses with the egg cell to form a diploid zygote. The second male gamete fuses with the diploid secondary nucleus present in the central cell. This fusion of three haploid nuclei (one male gamete and two nuclei in the secondary nucleus) inside
the embryosac is called triple fusion. Triple fusion takes place inside the embryosac. The nuclei involved in triple fusion are one male nucleus and two polar nuclei which has formed a diploid secondary nucleus.
5. Describe the essential floral parts of plants belonging to Liliaceae.
A: Androecium and gynoecium are the essential floral parts. In Liliaceae the androecium and gynoecium show the following features:
Androecium: Six stamens in two whorls of three each, free or epiphyllous (attached to
tepals), anthers are dithecous, basifixed, introrse and show longitudinal dehiscence.
Gynoecium: Tricarpellary, syncarpous, ovary superior, trilocular with ovules on axile placentation. Style is terminal, stigma trifid or capitate.
6. Describe the essential organs of Solanaceae.
A: Androecium and gynoecium are the essential organs in the flowers of Solanaceae.
Androecium: There are five stamens alternating with petals in epipetalous condition. The filaments are long. The anthers are dithecous, basifixed and introrse.
Gynoecium: Bicarpellary, syncarpous gynoecium with bilocular (unilocular in chillie) superior ovary with many ovules on swollen axile placenta. The carpels are arranged obliquely at 45°. Terminal style and stigma capitate.
7. Give economic importance of plants belonging to Fabaceae.
A: Economic importance of Fabaceae: The plants are a good source of proteins (pulses).
Ex: Cajanus, Cicer
Pods of beans are used as vegetables. Ex: Phaseolus
Edible oil is obtained from soya bean and groundnut. Ex: Arachis
Timber is produced by rose wood. Ex: Dalbergia
Blue dye from Indigofera and yellow dye from Butea are obtained.
Derris is used in medicine. Crotalaria, Phaseolus are used as fodder. Sesbania and Tephrosia are used as green manure.