Book : Botany
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Posted by: CHELSEA
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Writer CHELSEA

Marchantia Lifecycle

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Introduction

The plant body is dorsiventrally flattened, dichotomously branched. Thallus consists of distinct mid rib. On dorsal surface of mid rib, cup shape structure are found called gemma cups. These cups enclose reproductive bodies called gemmae. Ventral surface of thallus bears two types of structure – rhizoids and scales. Rhizoids are unicellular and unbranched. They are two types smooth walled and tuberculated. Scale are multicellular. They arrange in two rows on each side of mid rib.Internal structure- Vertical section of thallus has two distinct regions upper photosynthetic and lower storage region. Photosynthetic region is called assimilatory region. It consists of single layered epidermis, air pore, air chamber and assimilatory filament.Storage region present below the photosynthetic region. It is thick at mid rib and thin at margin. It consists of parenchymatous tissue which stores the food in the form of starch. In ventralsurface covered by lower epidermis. It consists of scale and rhizoids.

Vegetative Reproduction


Fragmentation- The older part dies and break branch of thallus. Each fragment of grow into new thallus. Adventitious branches- adventitious branch develop from ventral surface of thallus. The adventitious branches separate and each branch form a thallus. Gemma- it is a special mode of vegetative reproduction. In Marchantia gemma are develop inside the gemma cup. Gemma cup is a small cup like structure that develops on the dorsal side of thallus along with midrib. Gemma has small stalk and a multicellular discoid body. The body consists of two notches on the lateral sides. Gemma also possesses mucilage cells, oils cells and rhizoid cells. After maturation, mucilage hair absorb water and swollen up which creates an upward pressure. The pressure causes detachment of gemma from stalk. If they are carried to suitable substratum and gives rise to thallus.

Sexual Reproduction


In Marchantia, male and female reproductive organ are produce in different thalli. Male sex organ is called antheridiophore and female sex organ is called archegoniophore. Antheridiophore Antheridiophore are eight lobed receptacles. Receptacle consists of antheridal chamber and air chambers alternately. Each antheridal chamber consists of a antheridium. Mature antheridium is oval or conical structure present on short multicellular stalk. Single layered cell enclosed a mass of cells called androcytes. Each androcytes develop into a biflagellated antherozoid. Ruptured outer single layered jacket and release out antherozoid.

Archegoniophore

Archegoniophore consists of nine fingers like structures called rays. Archegonium occurs in ventral surface of lopes. Each archegonium is covered by a sheath called perigynium. Mature archegonium is flask shape structure swollen base with egg and ventral canal cell; narrow elongated neck with neck canal cell.

Fertilization

Ventral canal cell and canal cell disintegrate to produce mucilage which absorbs water and swells up. It creates pressure which results in the separation of cover cells. Many antheroziode enter into archegonium but only one unites with egg to form zygote.

Development of Sporophytes

Zygote divides and redivides to form embryo and embryo give rise to sporophyte. Each sporophyte is differentiated into foot seta and capsule. Foot: it is a basal part of sporophyte. It helps to absorption of food from gametophyte. Seta: the region between foot and capsule is called seta. It helps dispersal of spore. Capsule: capsule is oval in shape and it consists of spore and elaters. After maturation, spore are release out by ruptures the capsule wall.

Germination of Spore

The spore germination after falling on suitable substratum. Each spore germinates and forms a thallus. In life cycle of Marchantia, haploid gametophytic generation and diploid sporophytic generation come one after another to complete life cycle. So that, Marchantia shows alternation of generation.



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