Plant Form 
Plants might be grouped according to their form, such as a grass, flower, tree or shrub etc. The Raunkiær system is a common technical way of categorising plant life-forms and is based on the place of the plant's growth-point or bud.
Plant Hormones
These are molecules which have an influence over plant growth and development. Natural plant hormones are called phytohormones, whilst there are also manufactured synthetic hormones, all being typically referred to as plant growth regulators (PGR). Examples of plant hormones are auxins, cytokinins and gibberellins.
Plant Pathogen
An organism which infects a plant causing it harm.
Plant Renaming
Botanical names can change and evolve over time. The main reason for a change is due to a taxonomic reclassification where the plant is considered (at the time) to be more appropriately located elsewhere.
One example that can be used to show how a plant has been reclassified since it was originally credited to Carl Linnaeus as being the first person to describe it as Couch Grass.
Common Couch grass
1: Triticum repens L.
2: Agropyron repens (L.) Beauv.
3: Elymus repens (L.) Gould
4: It has also been classified as Elytrigia repens (L.) Desv. ex Nevski, but the current name used in the
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Plantae
A kingdom of eukaryotic organisms, mostly photosynthesizing ones, which includes green algae, mosses and vascular plants.
Ploidy
The number of complete sets of chromosomes within a plant cell: 2 sets of chromosomes are the norm for most grass species, with a normal species of perennial ryegrass, for example, having 14 chromosomes in each cell (these are called diploid plants or cultivars). Tetraploid cultivars (with 4 sets of chromosomes, 28 in each cell) of perennial ryegrass have also been bred. There are benefits and limitations for each type of ploidy depending on the required situation.
Plotless Sampling
This technique is mainly used for woodland, where individual plants can be more widely spaced out. There are four main methods of plotless sampling:
1. Point-centred quarter method: measures from the sampling point to the nearest individual in a quadrat. This is possibly the most accurate, but it can be biased where plants are evenly distributed.
2. Nearest individual method: measures from the sampling point to the nearest individual.
3. Nearest neighbour method: measures from the sampling point to the nearest neighbour of an individual. Requires identification of random individuals from wh
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Pollination
The transfer of pollen, from the anthers, to the stigma. This then starts the fertilisation process whereby a pollen tube is then formed from the stigma, which grows down in the style to the ovary, and then sperm cells are transferred down the tube for fertilisation to occur.
Polluter Pays Principle
The principle that the costs of environmental damage created by a production process, should be borne by the producer, i.e. the polluter.
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Polyculture