Marchantia is a genus of non-vascular land plants commonly included in bryophytes. Technically, they come under the family of Marchantiophyta which again comes under the clade of Embryophyta under the Kingdom Plantae. The organisms falling under the Marchantia classification are commonly known as liverworts.
It is quite evident for you now that as they are non-vascular they lack appropriate differentiation into leaves, stems and true roots. Due to that distinction, Marchantia has a plant body which is called a thallus, a common occurrence in plants lacking any vascular system such as algae and fungi. But the characteristics that make the Marchantia genus distinguishable are the small barrel-shaped pores for gaseous exchanges and cup-shaped structures called gemma cups for reproduction. As you read through, you will learn more about these structures.
There are different characteristics that define various qualities and stages of the life of Marchantia classification. We will look at them one by one.
Let's start with structural characteristics. Already from above, you know that the plant body of the liverworts is thalloid. Even though it is flat, the thalloid body in this scenario is dorsiventral i.e. it has different upper and lower surfaces. The epidermal layer forms the dorsal or the upper surface while the ventral surface is composed of multicellular purple-coloured scales of single-cell thickness and unicellular rhizoids. Apart from that structurally this thalloid can be divided into two layers - (1) Photosynthetic part and (2) Storage part.
1. Photosynthetic Part: It is the dorsal part i.e. the surface part of the Marchantia thalloid. It consists of the openings of the barrel-shaped pores for gaseous exchange and has a well-defined epidermis. It also contains the cup-shaped gemma cups.
2. Storage Part: It is the lower part of the thalloid. It consists of the chambers present of the pores that are mentioned above.
The given Marchantia diagram depicts its structural qualities.
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As mentioned above, there are cup-shaped structures called gemma cups that are present on the thallus of Marchantia which are useful in the process of reproduction. But those structures are for the asexual mode of reproduction. An important feature of Marchantia reproduction is that it can be both asexual as well as sexual.
The asexual reproduction in the liverworts is carried out by the gamma cups. These gamma cups are present on the upper side of the dorsal side of the thalli. They contain gemmae which can be a single cell or a group of cells that develop into a new individual after detaching from the parent. In this case, when the rainwater fills the gamma cups, it spills out the gemmae and these gemmae when spread into the nearby region develop into a new independent plant.
This kind of Marchantia reproduction is classified under fragmentation asexual reproduction occurring via the gemmae. You should also know that the asexual reproduction in Marchantia also occurs when older parts of the plant die and the newer ones that survive develop into a new identical organism.
Even though Marchantia reproduction can occur via asexual and sexual mode, you should know that the Marchantia are sexually dioecious i.e. the male and female reproductive systems are present on different thalli, not one. Thus, they are not bisexual in nature unlike most plants in Kingdom Plantae. Hence, in this mode, the female gametophytes present in a flask-shaped structure known as archegonium in the female plant are fertilised by the sperm from the antheridia on the male plant.
For the facilitation of the fertilisation, the archegonia swell after absorbing water and oozes out the neck canal cells and ventral canal cells. These discharged canal cells fuse and form a mucilaginous mass which contains chemical messengers that trigger a chemotic response in the male sperm known as the antherozoids. These antherozoids get attracted towards the archegonia and ultimately one of them fuses with the egg present in the archegonia/archegonium. A diploid zygote is formed by the fusion of the male and female nuclei.
The zygote over a period of time develops into a small sporophyte, which produces small spores. This sporophyte is dependent on the mature or larger gametophyte in whom the fertilisation takes place. The spores produced in time become independent male and female liverworts. You should note down that even though the zygote was diploid, these spores are haploid cells and hence, the plants that grow from them are also haploid in nature. This haploid stage is the dominant phase in the life cycle of plants falling under Marchantia classification.
From the above, you can easily understand that the life cycle of plants falling under Marchantia classification is a cycle between the haploid and diploid phases. Hence, Marchantia is haplodiplontic. The free-living phase is the haploid phase wherein there is the production of the male sperm and female ovum. This is followed by the diploid phase where the multicellular sporophyte is developed from the mitotic division of the zygote. During this cycle, the sporophyte as you already know is dependent on the mature gametophyte for nourishment and development. The sporophyte then produces spores which are haploid and formed by meiosis. These haploid spores now develop into new independent individual male and female organisms and the characteristic cycle continues.
Having gone through the short introduction about Marchantia it may interest you into further studying for the liverworts and their attributes. Understanding this introduction will provide you with a scientific reason, as to why you find the liverworts mostly in the moist and shady places because of the essential requirement of water for its life cycle and various other Marchantia characteristics.
1. What Type of Plant is Marchantia?
Ans: Marchantia is a genus of thalloid plants belonging to the family of Marchantiophyta. They are most commonly known as liverworts, a kind of moss, and are most commonly found in moist places for the availability of water as water plays a significant role in their life-cycle.
2. How Do Liverworts Get Nutrients?
Ans: Liverworts require water to survive and carry out most of their life processes. Hence, they need to be present at moist places which makes water availability easy as they lack proper differentiated organs such as stems, leaves and true roots.