haplostele – consisting of a cylindrical core of xylem surrounded by a ring of phloem. An endodermis generally surrounds the stele. A centrarch (protoxylem in the center of a metaxylem cylinder) haplostele is prevalent in members of the rhyniophyte grade, such as Rhynia. [6]

(a) Haplostele: This is the most primitive type of protostele. Here the central solid smooth core of xylem remains surrounded by phloem (e.g., in Selaginella spp.). (b) Actinostele: This is the modification of the haplostele and somewhat more advanced in having the central xylem core with radiating ribs (e.g., in Psilotum spp.). (c) Plectostele:

(a) Haplostele This is the most primitive type of protostele. Here the central solid smooth core of the xylem remains surrounded by uniform layers of phloem (e.g., in Selaginella spp., Gleichenia, Lycopodium).

Jan 12, 2025 · Brebner (1902) suggested that protostele may be of two types- Haplostele and actinostele. In the haplostele, there is a smooth circular core of the xylem and the phloem forms a continuous layer surrounding it. Eg. Selaginella. A haplostele is supposed to be the most primitive than the actinostele.

Mar 11, 2020 · Furthermore, the three types of protostele arrangements are haplostele, actinostele, and plectostele. In the haplostele, a cylindrical core of xylem is present and a cylindrical ring of phloem surrounds it.

Haplostele: This is the most primitive type of protostele. Here the central solid core of xylem is surrounded by a layer of phloem, e.g., Salaginella sp. b. Actinostele: Central xylem core with radiating ribs or a star shaped appearance surrounded by phloem.

Ø There are FIVE types of protosteles in Pteridophytes, they are: (a) Haplostele, (b) Actinostele, (c) Plectostele, (d) Mixed protostele and (e) Mixed protostele with pith. (a). Haplostele. Ø A protostele with a smooth core of xylem surrounded by uniform layers of phloem. Ø Named by Brebner in 1902.

A protostele having a central smooth core of xylem (almost circular in transverse section) surrounded by the phloem and the pericycle is known as haplostele (Fig. 1A) e.g., Rhynia, Selaginell, chrysocaulos, S.kraussiana.

haplostele (ectophloic protostele) A monostele type of protostele in which in cross-section the xylem occurs as a central strand surrounded by the phloem. Compare ACTINOSTELE, HYPOPHLOIC HAPLOSTELE, and SOLENOSTELE.

haplostele A * protostele in which the central core of xylem is circular when seen in transverse section. This is believed to be the most primitive type of protostele and was present in the earliest vascular plants, e.g. Rhynia.