Ectocarpus BSc (Hons) Part I Prepared by- Paper I – CRYPTOGAMS Dr. Jyoti Pandey Systematic Position: Fritsch (1945) Lee (1999) Class-Phaeophyceae Phylum-Phaeophyta Order-Ectocarpales Class-Phaeophyceae Family-Ectocarpaceae Order-Ectocarpales Genus – Ectocarpus Family- Ectocarpaceae Genus - Ectocarpus Order Ectocarpales- Ectocarpales include about 60 genera which inhabit cold sea of temperate and polar regions. It is the least specialized and most primitive group of Phaeophyceae where majority of the plants are annuals. The body plan is heterotrichous with prostrate creeping disc holdfast and monosiphonous filament making erect system. The plant body exhibits great range of morphological diversity. The group has simple filamentous types as in Ectocarpus siliculosus as well as relatively elaborate forms with compact filaments. The growth is trichothallic and the cell divisions are intercalary. Reproduction is isogamous as in E. siliculosus to anisogamous as in E. secundus. Life cycle is diplo-haplontic, and is primarily isomorphic as in Ectocarpus sp. But in relatively advanced forms like Colpomania sinuosa, it is heteromorphic. The asexual reproduction takes place by zoospores formed in unilocular and plurilocular sporangia. Habit and habitat It is of worldwide distribution preferring temperate waters. It grows attached to rocks and stones but may occur as an epiphyte attached to other algae and plants. Ectocarpus fasciculatus is epizoic and grows on the fins of certain fish. Some species are epiphytes on other algae like 1 members of Fucales and Laminaria. E. dermonematus is endophytic species. Ectocarpus is normally fixed to the substratum but it may be detached, surviving as a floating thallus. Thallus Structure: Genetically the thalli may be haploid or diploid. But both the types are morphologically alike. The thallus consists of profusely branched uniseriate filaments. It shows heterotrichous habit. There are two systems of filaments. These are prostrate and projecting system. The filaments of the projecting system arise from the filaments of prostrate system • a) Prostate system: The prostrate system consists of creeping, irregularly branched filaments. These filaments are attached to the substratum with the help of rhizoids. This system enters the host tissues in epiphytic conditions. Prostrate system is poorly developed in free floating species. • b) Projecting system: The projecting system arises from the prostrate system. It consists of well branched filaments. Each branch arises beneath the septa. The main axis and the branches of the projecting system are uniseriate i.e. joined end to end. In many species the terminal portion of a branch may end in a colourless hair with a basal meristem. In some species the older portions of main axis are ensheathed (corticated). This sheath is formed of a layer of descending rhizoidal branches. Structure of Cell: The cells are small. They are cylindrical or rectangular and uninucleate. 2 The cell wall is differentiated into two layers, the inner firm layer is made of cellulose and the outer gelatinous layer contains alginic acid. These are characteristic gelatinous substances of the walls of brown algae. The chromatophores may be ribbon-like with irregular outline or discshaped. Pyrenoid-like bodies-are associated with the chromatophores. The dominant pigment of Ectocarpus is fucoxanthin. It gives this algae golden brown colour. The other photosynthetic pigments are chlorophyll-a, -c, beta -carotene and other xanthophylls. All other eukaryotic organelles are present. Fucosan vesicles or granules are present in large number along with pyrenoid like bodies in the cell. The reserve food material is in form of laminarin and mannitol. Growth Growth of filaments in projecting system may be intercalary or apical • a) Intercalary: In some species, an intercalary meristem is present in the base of the hair. It is called trichothallic meristem. It increases the length of the terminal hair and vegetative cell of the branch. This growth is called trichothallic growth. • b) The growth in the prostrate system is apical …………………………………………………………..end of PART 1 Ectocarpus 3 .