One of which gives rise to the embryo sac. Polygonum Type - Monosporic Embryo Sacs. Development of the Polygonum-Type Embryo Sac The Polygonum-type pattern illustrated in Figure 2 is the most commonly observed form of embryo sac development. The embryo sac is formed from the chalazal megaspore in the tetrad and is eight-nucleate. (a) Polygonum type – Polygonum type is the normal type of development of embryo sac. Best Answer. Therefore, the resulting embryo sac is a seven-celled structure consisting of one central cell, one egg cell, two synergid cells, and three antipodal cells. The functional megaspore enlarges. This embryo sac has four well-defined megaspores. In the monosporic, or Polygonum-type embryo sac, meiosis of the diploid megaspore mother cell in the nucellus produces four haploid megaspores. It develops from chalazal functional megaspore (4th from micropyle). Therefore, it is also called as Polygonum type. Nucleus of functional megaspore divides by three mitotic divisions to form 8 nuclei, out of which pblygonum- Its nucleus divides. The development of the embryo sac begins with elongation of the functional megaspore. An eight nucleated and seven celled embryo sac formed from a single megaspore is called polygonum type. The embryo is small (usually less than one quarter of seed volume), axile (radially sectioned), linear (longer than broad) or rarely rudimentary (tiny relative to endosperm) depending on placentation type, and straight, bent, curved or curled at the upper end. Approx- imately 70% of the species examined, including Arabidopsis and maize, have this form of embryo sac (Russell, 1978; Mansfield et ai., 1990; Webb and Gunning, 1990). Assertion : 7-celled, 8 nucleate and monosporic embryosac is called polygonum type of embryo sac
Reason : It was discovered by Hofmesister for the first time in polygonum. Thus the daughter nuclei move to the micropylar and chalazal poles of the embryo sac. These two nuclei again divide so that the number of nuclei increases to four. Strasburger was the first to study such embryo sac. Based on the number of megaspores, embryo sacs can be divided into three types: monosporic, bisporic, and tetrasporic (Web Figure 21.3.A). Other articles where Polygonum type is discussed: angiosperm: Ovules: …megasporogenesis and megagametogenesis, called the Polygonum type, occurs in 70 percent of the angiosperms in which the life cycle has been charted. The normal type of embryo sac development has been studied in Polygonum by Strasburger. embryo sac can be "easily", if at all possible, be concluded from Polygonum-type embryo sac. A large vacuole is formed between the nuclei. [2] [3] The bisporic and tetrasporic patterns undergo varying processes and result in varying embryo sacs as well. 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