Eight nucleate embryo sacs area)Always tetrasporicb)Sometimes monosporic, bisporic and tetrasporicc)Always monosporicd)Always bisporicCorrect answer is option 'B'. Can you explain this answer?

Question

Answer

Embryo sacs can be divided into three types: monosporic, bisporic, and tetrasporic. In the monosporic, or Polygonum-type embryo sac, meiosis of the diploid megaspore mother cell in the nucellus produces four haploid megaspores.

Answer

Generally, only one megaspore takes part in the formation of the embryo sac nd is known as monosporic. But in some angiosperms, the embryo sac may be monosporic, bisporic, tetrasporic depending upon the no. of megaspores taking part in the formation of the embryo sac. Hope uh got it :)

Answer

Embryo sacs are female gametophytes that develop within the ovules of flowering plants. The development of embryo sacs involves meiosis, mitosis, and cellular differentiation, and the number of nuclei and cells in the mature embryo sac varies among different plant species.

Eight nucleate embryo sacs refer to the type of embryo sac that contains eight nuclei, which are distributed among seven cells. The eight nuclei consist of one egg cell, two synergids, three antipodal cells, and two polar nuclei that fuse to form a central cell.

The formation of eight nucleate embryo sacs can occur through different modes of megasporogenesis and megagametogenesis, which determine the number of meiotic events and the number of functional megaspores that give rise to the embryo sacs. These modes are:

1. Monosporic: This mode involves the development of a single functional megaspore from each megasporocyte after meiosis. The megaspore undergoes three rounds of mitosis to form the embryo sac, which contains eight nuclei. Most angiosperms use this mode of megagametogenesis.

2. Bisporic: This mode involves the development of two functional megaspores from each megasporocyte after meiosis. One of the megaspores undergoes three rounds of mitosis to form the embryo sac, while the other degenerates. Some species of grasses and sedges use this mode of megagametogenesis.

3. Tetrasporic: This mode involves the development of four functional megaspores from each megasporocyte after meiosis. Three of the megaspores degenerate, and the remaining one undergoes three rounds of mitosis to form four embryo sacs, each containing eight nuclei. Some species of flowering plants, such as Polygonum and Allium, use this mode of megagametogenesis.

Therefore, eight nucleate embryo sacs can be monosporic, bisporic, or tetrasporic, depending on the mode of megasporogenesis and megagametogenesis. Option B is the correct answer.

Answer

C

Answer

Its wrong .Polygnum embryo sac  is always  monosporic

Answer

Based on the number of megaspores, embryo sacs can be divided into three types: monosporic, bisporic, and tetrasporic ... In tetrasporic embryo sacs, cell plates fail to form after both meiotic divisions, resulting in a single four-nucleatemegaspore.

Answer

B

Answer

Correct answer is option 'B'

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