Wednesday, 26 May 2021

Sporangial development is seen in Salvinia

 Sporangial development is seen in Salvinia

Actinopteris radiata. Presence of sieve tubes have also been reported in the phloem of Equisetum anense and E. giganteum.or forms the stalk of the sporangium; this type of sporangial development is seen in Salvinia, whereas the inner cell either remains inactive Marsilea sporangia are present within specialized Lycopodium, Pteris) or heterosporous.

 In aquatic forms like Azolla, Isoetes, Salvinia. Plants are either homosporous (e.g., Equisetum, Pteridophyte structures, called sporocarps, Selaginella, Marsilea, Salvinia). initials and an inner layer of primary sporogenous cells; the jacket initials eventually form the multi-layered wall of the sporangium.

Whereas the primary sporogenous cells, by repeated divisions, give rise to spores: this type of sporangial development is found in Psilotum, Lycopodium, Selaginella and Equisetum or Leptosporangiate from a single initial cell which divides transversely into an outer and an inner cell.

The entire sporangium develops from the outer cetr the sporangium develops Marsilea, Pteris, etc. (i) Simple sorus : In this type of sorus all sporangia appear, grow and mature at the same time (e.g., Botrychium, Ophioglossum.)

  The spore wall is differentiated into an outer exine and an inner intine. The exine consists of an outer layer or ectin, composed of radially placed columnar rods, called columellae and inner relatively thin and uniform endine. The free and fused ends of columellae form various patterns on the spore wall which may be of taxonomic utility. 

The spore, germination, gives rise on to gametophytic generation. The germination of spore may be bipolar (e.g., Lycopodium, Equisetum), tripolar (e.g., Hymenophyllum) or amorphous or irregular (e.g., Angiopteris).

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