photosynthesis

The synthesis of carbohydrates from carbon dioxide and water by chlorophyll using light as energy and producing oxygen.

phytochrome

A bluish conjugated plant pigment protein that exists in two forms, Pr and Pfr, that absorbs red light and then initiates physiological responses such as germination, growth and flowering.

phytohormones

Any of the chemical substances produced in a plant in minute quantities which affect physiological processes, growth and development.

phytoplankton

Free-floating, mainly microscopic, photosynthetic organisms, such as algae, dinoflagellates, and diatoms, in aquatic systems.

pioneer species

The first members of a population to arrive in a new area, usually a bare, barren, uncolonized or disturbed environment. Pioneer species begin the process of ecological succession and are usually replaced by successional species.

pistil

The female organs of a flower comprising the ovary, stigma and style.

plant canopy

The more or less continuous layer of vegetation formed by the foliage and branches of plants.

plant nutrition

The nutritional elements, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur, essential for normal plant growth, development, and reproduction. They are usually derived from the soil.

plasmids

Extrachromosomal, usually circular DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in genetic engineering as cloning vectors.

pleiotropy

Phenomenon whereby a particular gene affects multiple traits

pollen

The fertilizing element of plants that contains the male gametophytes.

pulpwood

wood destined or suited for pulp manufacture, including standing or felled trees, logging residues, sawmill wastes, etc.

Q banding

Staining of bands, or chromosome segments, allowing the precise identification of individual chromosomes or parts of chromosomes.

quantitative polymerase chain reaction

Methods used for detecting the amplified DNA products from the polymerase chain reaction as they accumulate instead of at the end of the reaction.

Colloid

Organic and inorganic matter with very small particles size and a corrsponding large surface area per unit of mass.

Catena

A sequence of the soils of about the same age, derived from similar parent material, and occuring under similar climatic conditions, but having different characteristics due to variation in draining relief.

Chelating substance

Chelates are those micro-organic complexes which are soluble and readily absorbed by plants. These compounds are not converted to insoluble forms when applied into the soil. The metalic ions, commercially ch elated, are iron,copper,zinc and manganese. The most important and useful compounds for agriculture in chelated forms are ethylene diaminetetra acetic acid (EDTAA), diethylene triamine-purtautic acid (DTPA), cyclohexane diaminetetra acetic acid and ethylene diamine di-hydroxphenoxy acetic acid (EDDHAA).

Chlorosis

A condition in plants leading to failure in chlorophyll formation in which the colour of leaves range from light green through yellow to almost white.

Capillary water

This the water retained in the fine soil capillaries after seepage and percolation proceeesses are over. It is available from of water for all biological activities and is held at 0.33 atmosphere i.e. between field capacity and hygroscopic coefficient.

Consumption use of water

It is the amount of water required by plants to meet their need for water In transpiration and growth. It is also referred as evapotranspiration.