The quiescent center is present at the root tip (root apex) of a vascular plant. The quiescent is a region of apical meristem in the root of vascular plants that comprises very slowly dividing or nondividing (quiescent) meristematic cells. Cells in this region resume the meristematic activity if the cells surrounding the quiescent get damaged.
The number of cells present in the quiescent center is about 1,000. The rate of synthesis of DNA is very less in these cells due to which they divide very slowly.
The photoperiodic response to the red (~700 nm λ) and far-red (700-750 nm λ) wavelength of light is mediated by the phytochromes. Phytochromes are a superfamily of photosensory receptors found both in eukaryotes (plant, fungi) and prokaryotes (bacteria). They are present in plants and algae as dimers (monomer molecular weights 120 kDa). They are encoded by phytochrome (PHY) genes in plants and green algae.
Phytochromes absorb the red and far-red wavelength of light in the region of the visible spectrum. They are of two types i.e. Type I that activated by far-red light (700-750 nm λ) and Type II that is activated by red light (~700 nm λ).
Fern is a noflowering vascular plants. Fern possess vascular tissue such as xylem and phloem. As they are nonflowring plants they do not produce seed and reproduce by spores. One of the important characteristic of fern is circinate vernation.
The green photosynthetic leaf in fern is called as the frond. The new leaf in the ferm is starts from a coiled or rolling arrangement of leaves in the bud called Circinate vernation. Circinate vernation or arrangement protects the growing tip of the frond.
Parallael type of venation is found in the monocot plants. Reticulate type of venation is found the dicot plants.
Elongation in the stem of grasses (monocots) after initial growth is due to the intercalary meristem. Meristems are tissues found in plants that consist of undifferentiated cells and have the ability of cell division. Meristematic tissues can give rise to other kinds of plant tissues and organs.
The intercalary meristems are present in the monocot plants. They are usually present at the leaf blades and base of nodes. The intercalary meristems undergo cell division and help in the growth of monocot plants. In bamboo, the rapid stem elongation is due to the intercalary meristems present at the nodes. Intercalary meristems are associated with the growth in the middle position of the stem.
Vascular tissues are the main conducting tissue primaryly composed of the xylem and phloem.
German botanist Johannes Hanstein (1822 – 1880) proposed the Histogen theory in 1868. The Histogen theory postulated that the shoot apex consists of three meristematic zones.
They are Dermatogen, Periblem and Plerome. The outermost layer is the Dermatogen and gives rise to the epidermis. The middle is the Periblem and gives rise to the cortex. The Plerome is the innermost layer of tissue that gives rise to vascular tissues.
The auxanometer is an instrument used for the measurement increase of growth (length) of plants. The term derived from the words auxain means “to grow” and metron means “measure”. The auxanometer is very sensitive and can measure the growth of plants as small as a micrometer (µM).
The auxanometers are used in laboratories to measure the change rate of growth of plants under various environmental or physiological conditions. German botanist Julius von Sachs (1832 – 1897) made a significant contribution to the development of various kinds of Auxanometers. They are (i) Arc- indicator, (ii) Autographic auxanometer, and (iii) Cathetometer apparatus.
The membrane that surrounds a vacuole of a plant cell is known as tonoplast. The tonoplast separates the contents of the vacuole from the cytoplasm in a cell. A vacuole is usually found in the plant, fungal cells as well as in some protists and microorganisms. Hugo de Vries in 1885 used the term “tonoplast” for the vacuolar membrane.
The tonoplast is a semipermeable membrane. The tonoplast possesses various transport proteins, proton pumps (the V-ATPase and V-PPase), aquaporins, and ion channels. Thus, tonoplast maintains the osmolytes concentration, storage of metabolites, metal, and nonmetal ions as well as water balance and maintains turgor pressure inside the cell.
The fleshy edible part of the apple fruit is the thalamus. Apple (Malus domestic) fruit is a pome or false fruit. The outer fleshy edible part of the apple is the receptacle or thalamus. Pome type of fruit is mainly produced by flowering plants belonging to the family Rosaceae.
The pome is an accessory fruit that contains one or more carpels and is surrounded by accessory tissue (the receptacle or the thalamus). The skin of the fruit is called the epicarp, the flesh of the fruit is called the mesocarp and the core of the fruit is called the endocarp.