Sexual Reproduction in Flowering Plants Test - 4

• Homogamy: The anther and stigmas of a bisexual flower mature simultaneously.
  The pollen grains reach the mature stigma either by contact, wind, gravity, raindrop, or even insects.
• Self-pollination brought about by contact is called autogamy and remaining agencies perform indirect autogamy.

The flower which contains either male or female reproductive part is called a unisexual flower.
Papaya plant produces either male or female flower in separate plants.

Hybridisation is the process to develop hybrid plants with desired traits. In bisexual flower, the stamen is removed with the help of forceps to avoid self-pollination. This method is called emasculation.

Bisexual flower have four main parts. Pistil or carpel is located at center followed by stamen, carpel and sepals. Pistil contains stigma, style and ovary.

The flower in which pollen grain is transferred from anther to stigma of anther flower by insects are colorful to attract insects and contain nectar.

• A germ pore is a small pore in the fungal pore’s outer wall from which the germ tube then exits at germination. If its location is taken into consideration then it can be apical or eccentric.
• Germ pore plays an essential part in the fertilization of plants. It helps in pollen tube formation and releases the male gamete during fertilization.

Angiospermic embryo sac is 8-nucleate but 7-celled at maturity. This includes 3- celled egg Synergids, 3 antipodal cells and 2 polar nuclei.

Ovule/s are located inside the ovary. The point of attachment of the ovule to the ovary is called the funicle. Funicle extends to hilum as stalk.

The female gametophyte in angiosperms is called Embryo sac. It contains egg apparatus, antipodal cells and polar nuclei. After fertilisation embryo sac changes into seed.

In ovule female gamete is formed at micropylar end and three antipodal cells at chalazal end. The two central nuclei are called polar bodies that fuse with one of male gamete to form endosperm.

Maize flower is pollinated by winds. The transfer of pollen grain from anther to stigma by wind is known as anemophilus.

Lotus is an aquatic plant but the flower of lotus is outside and above the water surface. So, it cannot be pollinated by water. It is generally pollinated by insects.

The transfer of pollen grain from anther to stigma is called pollination. Pollination is caused by winds, insects, water, and some other means. Insect pollinated flowers are called Entomophilous flowers.

About 60% of angiosperms, pollen grains are shed at two celled stage. The larger cell is called vegetative cell and the smaller one is called generative cell. Each generative cell produces two male gametes.

Anther is bilobed structure at the tips of stamen. Each lobe consists of two theca. Each theca change into microsporangium. Anther forms four sided structure having four microsporangia in which pollen grains are formed.

Endosperm is present around the growing embryo. It provides nutrition to the growing embryo. In leguminous plants, it is completely consumed by the embryo and nothing remains in seed as in pea.

PEN (primary endosperm nucleus) divides into two nuclei and subsequent division of nucleus produce large number of nucleus without cell wall formation. These types of endosperm are called free nuclear type of endosperm.

Double fertilisation involves fusion of one male gamete with egg during Syngamy and fusion of two polar nuclei with other male gametes. So, total 5 nuclei are involved in double fertilisation.

Maize grain is monocotyledonous, having a single cotyledon. This cotyledon is also called scutellum.

The part of axis above the level of attachment of scutellum is called epicotyl. It has as shoot apex and few leaf primordia enclosed in a hollow foliar structure called coleoptile. Epiblast represents rudiments of second cotyledon.

The seedless fruit develops without fertilisation by using some plant hormones. The fruit so formed are called parthenocarpic.

Placenta is located inside the ovarian cavity. It help in transport of nutrient to megasporangium or ovule. Ovule is attached to placenta by means of stalk called funicle.

Seeds dispersed by water are contained in light and buoyant fruit, giving them the ability to float. Coconuts are well known for their ability to float on water to reach the land where they can germinate. The coconut seed is especially well adapted to increase its range by the method of ocean dispersal. The seed floats when its outer layers dry out. The buoyant coconuts drift on ocean currents and end up on tropical beaches where they germinate and take root.

• True Fruit: A true fruit is one that develops only from the ovary. 
  Example: Mango, Coconut, Zizyphus etc.
• False Fruit or Pseudocarp: In some fruits, it is not the ovary that forms the fruit. In fact, some other parts of the flower, like the thalamus, inflorescence, calyx are modified to become a part of the fruit. These types of fruit are called false fruits. 
  Example: Apple, Strawberry etc.

The study of fruits and their cultivation is known as pomology. This is one of the fasted growing fields of horticulture combined with genetically modified fruits.