Sexual Reproduction in Flowering Plants Test - 3

• The exine of the pollen grain is made of sporopollenin. Sporopollenin is one of the most resistant organic compounds.
• It can withstand high temperature, strong acids, and alkalis and cannot be degraded by any of the known enzymes.
• Hence, it acts as a shield and protects the pollen grain from getting damaged.

Structure of pollen grain:

Embryo sac: The female gametophyte of flowering plants, which produces the two female gametes – the egg cell and central cell – for double-fertilization by the two sperm cells of the male gametophyte (pollen grain).

First we should know about germ pore to answer this question.

• A germ pore is a tiny pore in a fungal spore’s outer wall. It can be apical or eccentric in its position, and can be visualised as a lighter coloured region on the cell wall on light microscopy. The mushroom spore that has a pore at one end is the apical germ pore.

Now, let us find the solution from the options:

• A germ pore is a small pore in the outer wall of the fungal pore from which the germ tube comes out.
• Water is absorbed by the embryo in the seed germination process, which results in the cells being rehydrated and extended. Thus, the option A is incorrect.
• The root of a number is a radical, which may be square roots, cube roots, and so on. A radical is sometimes considered a square root. Any function identified by a root is a radical function. Thus, the option C is incorrect.
• The germ pore plays an important function in plant fertilization. It assists in the creation of pollen tube and releases male gametes during fertilisation.

Thus, the correct answer is option ‘D’ Initiation of pollen tube.

Generative cell which is a cell of the male gemetophyte or pollen grain in seed plants that divides to give rise directly or indirectly two male gametes.

Additional information:

• Each pollen grain contains vegetative or non-reproductive cells and a generative cell or reproductive cell.
• In flowering plants, the vegetative tube cell produces the pollen tube, and then the generative cell divides to produce two sperm cells or male gametes.
• Pollens present in these microsporangia. The microsporangia are also called pollen sac.
• It is also said that the pollen sac develops from a parent cell called the archesporial cell.
• The archesporial cell is divided into the outer and inner layers.
• The inner layer produces the sporogenous tissue which eventually forms the pollen mother cell.
• This sporogenous tissue is surrounded by the tapetum layer which provides nourishment to the pollen or microspore mother cell present within the sporogenous tissue.
• The microspore mother cell is diploid and divides meiotically to make haploid microspores of pollen. This describes the method of microsporogenesis.

So, the right answer is option D that is Generative cell.

• Megaspores are produced by meiosis in the megaspore mother cells. Megaspore then develops into a female gametophyte or embryo sac.
• Megagametophyte or the female gametophyte is the embryo sac that develops from the megaspore through megagametogenesis.
• Megasporangium is a structure that along with its protective coverings forms the ovule.
• The female gamete is the egg cell which upon fusion with the male gamete forms a diploid zygote.

Hence, embryo sac represents megagametophyte.

Starting from the innermost part, the correct sequence of parts in an ovule is egg, Embryosac,  nucellus, integument. This sequence can be seen in following

  A diagrammatic view of an ovule 

In angiosperms or flowering plants, the megasporocyte produces a megaspore that develops into an embryo sac through two distinct processes. 

• Megasporogenesis: formation of the megaspore in the nucellus, or megasporangium.
• Megagametogenesis: development of the megaspore into the embryo sac, or megagametophyte.

A synergid cell wall forms a highly thickened structure called the filiform apparatus at the micropylar end consisting of numerous finger-like projections into synergid cytoplasm. These synergid cells are necessary for pollen tube guidance in the ovule.

• The gynoecium represents the female reproductive part of the flower and consists of pistil.
• Each pistil has three parts, i.e., stigma, style and ovary. Inside the ovarian cavity, the placenta is located. Arising from the placenta there are the mega sporangia, commonly called ovules.
• The functional megaspore undergoing the meiotic division develops into the female gametophyte or embryo sac.
• In option 'b' thalamus is not a part of gynoecium. Thalamus is the part of flower which form the base on which all the floral whorls rest upon, it is not associated with gynoecium.
• In option 'c' tapetum is not a part of gynoecium. Tapetum is the inner most nutritive layer or microsporangium.
• In option 'd' stamens not a part of gynoecium. Stamen is male reproductive part (androecium) of plant. Therefore, the other options are wrong. 

• A plant having both reproductive organs in the same plant is known as monoecious plants. It may also be known as homothallic conditions.
• Dioecious plants are those which have only one reproductive organ, also known as unisexual plants. Another word for dioecious plants is heterothallic.

hence, Cucurbits and coconuts are examples of Monoecious.