Plant Biology and Classification

Vascular tissue in dicot stem consists of many vascular bundles which are arranged in the form of broken ring known as eustele.

The production of vast amount of grain is one of the most outstanding outcome of modern agriculture. Poaceae (monocot) and fabaceae (dicot) contribute to the species, that are responsible for the vast majority of grain production worldwide.

The earliest known flowering plants date back to about 130 million years ago. According to Cronquist (evolution and classification of flowering plants, 1988), the most primitive of all living angiosperms belong to the subclass Magnoliidae. This subclass contains several primitive plant families, including the water-lily family (Nymphaeaceae), buttercup family (Ranunculaceae) and magnolia family (Magnoliaceae). 

In pt eris antheridum is having (about 32) multiflagellated, coiled (2 - 3 coils) anthropoids or spermatozoids.

Option A is incorrectly matched - Therophytes are annual plants with surviving buds above soil, not 'well above'. Cryptophytes have buds underground, Hemicryptophytes have buds on soil surface, and Chamaephytes have buds at ground level.

Thallophytes lack differentiation of plant body into the stem and leaves. The plant body is called as a thallus. They lack vascular tissue, the sex organs are unicellular and when multicellular, all are fertile. Thus, the correct answer is option D.

Ulothrix is an example of division Thallophyta, while Funaria and Riccia are example of Bryophyta and Adiantum is an example of Pteridophyta. 

Stigeoclonium shows heterogeneous habit which differentiated into prostrate and erect system.

Ulva is a genus of edible green algae commonly referred to as sea lettuce due to its thin, flat, leaf-like thallus.

Non flowering plants are those plants which cannot produce flowers. They reproduce mainly through spores. Examples of non flowering plants include ferns, mosses and liverworts. They belong to cryptogams. Cryptogams are non flowering and seedless, spore-bearing plants. 

Thallophyta: salient features are- most primitive and simple plants. They do not possess a vascular system. The plant body is not differentiated into stem roots and leaves. The whole plant body remains in the form of an undivided mass of cells called thallus. The mode of nutrition is photosynthetic, parasitic or saprophytic. They reproduce both sexually and asexually. Asexual reproduction usually reproduction takes place by spore formation. Fertilization is not followed by embryo formation. The division Thallophyta includes two major classes, algae and lichens. 

The eyespot or stigma is a photoreceptive organelle found in the flagellate of green algae like Chlamydomonas and some other unicellular photosynthetic organisms such as euglenoids. It allows the cells to sense light direction and intensity and respond to it by swimming either towards the light (positive phototaxis) or away from the light (negative phototaxis). A related response occurs when cells are briefly exposed to high light intensity, causing the cell to stop, briefly swim backward, then change swimming direction. Eyespot-mediated light perception helps the cells in finding an environment with optimal light conditions for photosynthesis. Eyespots are the simplest and most common "eyes" found in nature, composed of photoreceptors and areas of bright orange-red pigment granules. Signals relayed from the eyespot photoreceptors result in alteration of the beating pattern of the flagella, generating a phototactic response.

According to the International Code of Nomenclature for algae, fungi, and plants, the names of suborders are formed by adding the suffix -ales to the stem of the name of the type genus.