Phospholipids The principal class of lipids that are present in cell membranes; phospholipids are diglycerides (i.e., two fatty acids attached to a glycerol “molecular backbone”) to which is also attached a phosphate group. The principal sites in plants of lipid and fatty acid biosynthesis (manufacturing) are the endoplasmic reticulum, chloroplasts, and the mitochondria. See also LIPIDS, PLASMA

MEMBRANE, CELL, FATS, FATTY ACID, PHOSPHATE-

GROUP ENERGY, ENDOPLASMIC RETICULUM (ER),

CHLOROPLASTS, MITOCHONDRIA.

Phosphorylation The introduction of a phosphate group into a molecule. Formation of a phosphate derivative of a biomolecule, usually by enzymatic transfer of a phosphate group from ATP. See also ADENOSINE TRIPH-

OSPHATE (ATP).

∆Phosphorylation Potential A b b r ev i a t e d

∆Gp, it is the actual free-energy change of ATP hydrolysis under a given set of condi-

tions. See also PHOSPHORYLATION, FREE ENERGY,

HYDROLYSIS, ADENOSINE TRIPHOSPHATE (ATP).

Photon A single unit of light energy. See also

PHOTOSYNTHESIS, PHOTOSYNTHETIC PHOSPHORY-

LATION.

Photoperiod The optimum length or period of illumination required for the growth and maturation of a plant. The photoperiod is distinct from photosynthesis. See also PHY-

PTOCHROME, CENTRAL DOGMA (NEW).

Photophore See BIOLUMINESCENCE.

Photophosphorylation See CYCLIC PHOTOPHOS-

PHORYLATION.

Photorhabdus luminescens A soil-dwelling bacterium that produces certain toxins (effective against a variety of insect pests), antibiotics, antifungal compounds, lipases, proteases, and bioluminescent (light-produc- ing) compounds. Photorhabdus luminescens naturally colonizes the gut of the Heterorhabditis nematode which attacks certain insect pests (tobacco hornworm, mealworm, cockroaches, etc.). When that nematode enters those insects, the Photorhabdus luminescens is released inside the insect, which is subsequently killed via the toxins secreted by P. luminescens. P. luminescens synthesizes (manufactures) a protein that is high in content of the amino acids methionine and lysine; and that protein constitutes approximately

50% of the total protein content of

P. luminescens. See also BACTERIA, ANTIBI-

OTIC, TOXIN, LIPASE, PROTEASE, BIOLUMINES-

CENCE, CORN, PROTEIN, METHIONINE, LYSINE.

Photosynthesis The synthesis (production) of bioorganic compounds (molecules) using light energy as the power source. The synthesis of carbohydrates (hexose) occurs via a complicated, multistep process involving reactions that occur both in the light (light reactions) and in the dark (dark reactions). In eucaryotic cells the photosynthetic machinery necessary to capture light energy and subsequently utilize it is contained in structures called chloroplasts, which contain the molecule that initially captures light energy, called chlorophyll. Chlorophyll appears green. Green plants synthesize carbohydrates from carbon dioxide and water, which are used as a hydrogen source. The synthesis reaction, which is light-driven, liberates oxygen in the process. Other organisms use this oxygen to sustain life. From initial carbohydrates, plants subsequently also synthesize (manufacture) other compounds (e.g., fatty acids).

Plants are not the only users of photosynthesis technology. Other organisms such as green sulfur bacteria and purple bacteria also carry out photosynthesis, but they use other compounds besides water as a hydrogen

source. See also CARBOHYDRATES, CHLOROPLASTS, ORGANISM, EUCARYOTE, HEXOSE, CYCLIC

PHOTOPHOSPHORYLATION, CAROTENOIDS, GOLDEN

RICE, FATTY ACIDS, BACTERIA.

Photosynthetic Phosphorylation Also called photophosphorylation, it is the formation of ATP from the starting compounds ADP and inorganic phosphate (Pi). The formation is coupled to light-dependent electron flow in photosynthetic organisms. See also PHOTON,

PHOTOSYNTHESIS, ADENOSINE	TRIPHOSPHATE
(ATP), ADENOSINE DIPHOSPHATE (ADP), CYCLIC
PHOTOPHOSPHORYLATION.
Phylogenetic Constraint T h e	l i m i t a t i o n s

inherent in an organism as a result of what its ancestors were. For example, a horse will never fly and an ape will never speak, because the ancestors of neither possessed those capabilities. See also GENOTYPE, PHENO-

TYPE, GENOME, MORPHOLOGY.

© 2002 by CRC Press LLC

	Physical Map (of genome) A diagram show-	past childbearing age), the chelating (“com-
	ing the linear order of genes or genetic mark-	bining”-with) property of the phytate-source
	ers on the genome, with units indicating the	inositol causes it to act as a beneficial anti-
	actual distance between the genes or mark-	oxidant in the human body; which can help
	ers. See also GENETIC MAP, GENE, GENOME,	to protect against certain cancers (e.g., pros-
	POSITION EFFECT.	tate cancer). See also PHYTASE, LOW-PHYTATE
	Physiology The branch of biology dealing	CORN, LOW-PHYTATE SOYBEANS, ENZYME, DIGES-
	with the study of the functioning of living	TION (WITHIN ORGANISMS), HIGH-PHYTASE CORN
	things. The materials of physiology include	AND SOYBEANS, PROSTATE, CANCER, ANTIOXI-
	all life: animals, plants, microorganisms, and	DANTS, CHELATION.
	viruses.	Phytic Acid Also known as phytate or inositol
	Phytase A digestive enzyme that is present in	hexaphosphate. See also PHYTATE.
	the digestive systems of many plant-eating	Phyto-manufacturing Refers to the produc-
	animals to enable breakdown of phytate	tion of valuable substances (e.g., polyhy-
	(also known as “phytic acid”). Phytase is	droxybutylate biodegradable plastic,
	sometimes present within the plant material	industrial-process enzymes, etc.) in plants
	consumed by animals. For example, phytase	(e.g., genetically engineered plants). See
	is naturally produced in the seed coat of	also POLYHYDROXYLBUTYLATE (PHB), BIOPOLY-
	wheat. See also ENZYME, DIGESTION (WITHIN	MER, POLYHYDROXYALKANOIC ACID (PHA),
	O R G A N I S M S ) , P H Y T A T E , H I G H - P H Y T A S E	EXTREMOZYMES, NUTRACEUTICALS.
	CORN/SOYBEANS, LOW-PHYTATE CORN, LOW-	Phyto-sterols	See PHYTOSTEROLS.
	PHYTATE SOYBEANS.	Phytoalexins	Term utilized to refer to chemi-
	Phytate A chemical complex (large molecule)	cal compounds (enzymes, etc.) that are pro-
	substance (inositol hexaphosphate) that is	duced by certain plants in response to the
	the dominant (i.e., 60–80%) chemical form	presence of infectious agents (e.g., fungus,
	of phosphorus present within cereal grains,	bacteria) or their products. From the Greek
	oilseeds, and their byproducts. Monogastric	words phyton, plant, and alexein, to defend;
	animals (e.g., swine) cannot digest and uti-	phytoalexins possess antimicrobial (i.e., fun-
	lize the phosphorous within phytate, because	gus-killing, bacteria-killing) properties, so
	they lack the enzyme known as phytase in	they can help plants to protect themselves
				P
	their digestive system so that phosphorus	against those microorganisms. See also PHY-
	(phytate) is excreted into the environment.	TOTOXIN, ISOFLAVONES, ALLELOPATHY, STRESS
	When phytase enzyme is present in the	PROTEINS, PHARMACOENVIROGENETICS, ANTIBI-
	ration of a monogastric animal, at a high	OTIC, PHYTOCHEMICALS, ENZYME, FUNGUS, BAC-
	enough level, the monogastric animal is then	TERIA, ISOFLAVONES, PATHOGENIC, MICROBE,
	able to digest the phytate (thereby “releas-	MICROBICIDE, SALICYLIC ACID (SA), PATHOGENE-
	ing” most of that phosphorus for absorption	SIS RELATED PROTEINS, SYSTEMIC ACQUIRED
	by the body of the animal). However, the	RESISTANCE (SAR).
	(cleaved-off, “free”) inositol that was “liber-	Phytochemicals A term used to refer to certain
	ated” (from six phosphate atoms per mole-	biologically active chemical compounds that
	cule of phytate) can then quickly chelate	occur in fruits, vegetables, grains, herbs,
	(“combine” with) other minerals in the feed	flowers, bark, etc. Phytochemicals act to
	ration (iron, calcium, zinc, etc.). Thus, low-	repel or control insects, prevent plant dis-
	phytate crop varieties (i.e., containing inher-	eases, and control fungi and adjacent weeds.
	ently smaller amounts of inositol) are less	Phytochemicals also sometimes confer ben-
	likely to chelate important dietary minerals	eficial health effects to the animals (e.g.,
	such as iron (which can exacerbate malnu-	humans) that consume the plant (portions)
	trition in typically iron-poor diets such as in	containing those applicable phytochemicals.
	developing countries where adequate iron	For example, vitamin C in citrus fruits, beta
	content/iron fortification of human diets is	carotene in carrots and other orange vegeta-
	not common). In adult humans (e.g., those	bles, d-limonene in orange peels, tannins in

© 2002 by CRC Press LLC

ESCHERICHIA COLIFORM,

PLANT

CARO-

PHOTO-

RPS6

green tea, capsaicin in chili peppers, n-3 (omega-3) fatty acids in soybean oil and fish oil, genistein, saponins, vitamin E, and phytosterols in soybeans, etc.

Beta carotene has been found to aid eyesight and may help prevent lung cancer. d-Limonene has been found to protect rats against breast cancer. Tannins appear to help prevent stomach cancer. Quercitin appears to help prevent prostate cancer. Capsaicin can reduce arthritis pain. N-3 (omega-3) fatty acids help to lower triglyceride levels in the blood. Genistein appears to block growth of breast cancer tumors, prostate cancer tumors, and to prevent the loss of bone density that leads to the disease osteoporosis. Tocotrienols act as antioxidants, and also inhibit synthesis of cholesterol (in humans). See also CANCER,

DEXTROROTARY (D) ISOMER, FATTY ACID, LINO-

LENIC ACID, LINOLEIC ACID, GENISTEIN (Gen),

BIOLOGICAL ACTIVITY, MOLECULAR PHARMING,

FLAVONOIDS, RESVERATROL, NUTRACEUTICALS,

CHOLESTEROL, N- 3 FATTY ACIDS, PHYTOTOXIN,

ALLELOPATHY, ANTIBIOTIC, PHYTOALEXINS, ANTIOXIDANTS, ABRIN, RICIN, PFIESTERIA PISCICIDA,

P H Y T O S T E R O L S , L I G N A N S , P O L Y P H E N O L S ,

SAPONINS, FRUCTOSE OLIGOSACCHARIDES, LYCOPENE, LUTEIN, ANTHOCYANIN, SOYBEAN PLANT,

SOYBEAN OIL, VITAMIN E, XANTHOPHYLLS, SITO-

STEROLS, CAROTENOIDS, STEROLS, ALICIN, ELLAGIC

PACID, PROANTHOCYANIDINS, CAFFEINE, QUERCITIN,

ROSEMARINIC ACID, ZEAXANTHIN.

Phytochrome A protein plant pigment that serves to direct the course of plant growth and development and differentiation in a plant. The response is independent of photosynthesis, e.g., in the photoperiod (length of light period) response. See also

PERIOD, PROTEIN, PHOTOSYNTHESIS,

HORMONE.

Phytoene See GOLDEN RICE, LYCOPENE,

TENOIDS.

Phytoestrogens C o m p o u n d s p o s s e s s i n g molecular structures somewhat similar to that of estrogen and that are naturally found in all plants on earth. As a result every vegetable, fruit, cereal and legume contains at least one type of “phytoestrogen.” For example, flavones and flavonols are beneficial phytoestrogens (mostly redand yellow-col- ored pigments) found in colored vegetables

and fruits (red grapes, yellow grapefruit, oranges, etc.). See also PHYTOCHEMICALS, FLA-

VONOIDS, FLAVONOLS, LIGNANS, SELECTIVE

ESTROGEN EFFECT, ISOFLAVONES, ESTROGEN.

Phytohormone See PLANT HORMONE.

Phytopharmaceuticals See PHYTOCHEMICALS,

NUTRACEUTICALS, PHYTO-MANUFACTURING.

Phytophthora megasperma f. sp. glycinea A strain of Phytophthora fungus that can infect the soybean plant [Glycine max (L.) Merrill] under certain conditions, and thereby cause that soybean plant’s stem and root to degrade (so-called “rot”). See also FUNGUS, PATHO-

GENIC, SOYBEAN PLANT, STRAIN, ISOFLAVONES.

Phytophthora Root Rot A plant disease that is caused by a certain phytophthora fungus (Phytophthora sojae). Some soybean varieties are genetically resistant to as many as 21 races/strains of phytophthora fungi. See also

FUNGUS, RPS1c GENE, RPS1k GENE, GENOTYPE,

STRAIN, PATHOGENIC, SOYBEAN PLANT,

GENE, ISOFLAVONES.

Phytophthora sojae See PHYTOPHTHORA ROOT

ROT.

Phytoplankton Algae that float or are freely suspended in the water.

Phytoremediation Refers to the use of specific plants to remove contaminants or pollutants from either soils (e.g., polluted fields) or water resources (e.g., polluted lakes). For example, the Brazil water hyacinth (Eichhornia crassipes) naturally accumulates in its tissues toxic metals such as lead, arsenic, cadmium, mercury, nickel, copper, etc., and so has been utilized as a “biofilter” (e.g., in India). Insertion of the Escherichia coliform bacteria gene known as gsh 11 into the plant known as Indian mustard causes that plant to accumulate 40–90% higher amounts of cadmium (from cadmium-tainted soil) in its tissues than before; such genetically engineered plants could be utilized to extract cadmium from polluted sites. See also BIOREMEDIATION,

BIORECOVERY, BACTE-

RIA, GENE, GENETIC ENGINEERING.

Phytosterols A group of phytochemicals (i.e., solid alcohols consisting of ring-structured molecules) that are present in seeds produced by certain plants (e.g., the soybean plant Glycine max L.). Evidence shows that human consumption of certain phytosterols

© 2002 by CRC Press LLC

can help to prevent certain types of cancers, and can help lower total serum cholesterol and low-density lipoproteins (LDLP) levels; thereby reducing the risk of coronary heart disease (CHD). Evidence indicates that those phytosterols (e.g., campesterol, stigmasterol, beta-sitosterol) interfere with absorption of dietary cholesterol by the intestines, and decrease the body’s recovery and reuse of cholesterol-containing bile salts, causing more cholesterol to be excreted from the body than previously. In 2000, the researcher Joseph Judd fed phytosterols extracted from soybeans (Glycine max L.) to human volunteers that were consuming a “low-fat” diet. Their total blood serum cholesterol and low-density lipoprotein (LDLP) levels decreased by more than 10% in a short time. See also PHYTOCHEMI-

CALS, STEROLS, SITOSTANOL, SOYBEAN PLANT,

LOW-DENSITY LIPOPROTEINS (LDLP), CHOLES-

TEROL, CAMPESTEROL, STIGMASTEROL, BETA-

SITOSTEROL, SITOSTEROL, CORONARY HEART DIS-

EASE (CHD).

Phytotoxin Any toxic compound produced by

a plant. See also ALLELOPATHY, ANTIBIOTIC,

PHYTOCHEMICALS, PHYTOALEXINS, TOXIN, ABRIN,

RICIN, PFIESTERIA PISCICIDA, SOLANINE, GLUCOSAMINES, PSORALENE, GLUCOSINOLATES, GOSSYPOL, ALKALOIDS.

Picogram (pg) 10–12 gram or 3.527 × 10–14 ounce (avoirdupoir). See also MICROGRAM.

Picorna A “family” of the smallest known viruses. The viruses of this family are a cause of the common cold and Hepatitis A in humans, one form of hoof and mouth disease in animals, and at least one disease in corn (maize). In 1994, Dr. Asim Dasgupta discovered a cellular molecule within ordinary baker’s yeast that prevents picorna virus reproduction. This advance could lead to the creation of a treatment, in the future, to cure one or more of the above-mentioned diseases after infection has begun. See also

VIRUS, CLADISTICS, CLADES.

Pink Bollworm See PECTINOPHORA GOSSYPIELLA.

Pink Pigmented Facultative Methylotroph (PPFM) A type of bacteria that is naturally present in virtually all plants. PPFM produces cytokinin, which aids the cell division (growth) process in plants. PPFM also

produces a chemical substance similar to vitamin B-12. In 1996, Joe Polacco discovered that impregnation of aged seeds with PPFM improved the germination (sprouting) rate of those aged seeds. See also BACTERIA,

MITOSIS, CELL DIFFERENTIATION, VITAMIN.

	Pituitary Gland One of the endocrine glands,
	it lies beneath the hypothalamus (at the base
	of the brain). Along with the other endocrine
	glands, the pituitary helps control long-term
	bodily processes. This control is accom-
	plished via interdependent secretion of hor-
	mones along with the other glands
	comprising the total endocrine system. For
	example, the pituitary helps control the
	body’s growth from birth until the end of
	puberty by secreting growth hormone (GH).
	Secretion of GH by the pituitary is itself
	governed by the hormone known as growth
	hormone-releasing factor (GHRF), received
	by the pituitary gland from the hypothalamus.
	The pituitary gland also helps control
	reproduction (development and growth of
	ovaries, timing of ovulation, maturation of
	oocytes, etc.) by secreting two gonadotropic
	(reproductive) hormones named luteinizing
	hormone (LH) and follicle-stimulating hor-
	mone (FSH). Secretion of LH and FSH by
	the pituitary is itself governed by the hor-
	mones gonadotropin-releasing hormone
		P
	(GnRH, received by the pituitary from the
	hypothalamus) and estrogen/progesterone
	(received by the pituitary from the ovaries).
	See also ENDOCRINE GLANDS, ENDOCRINE HOR-
	MONES, HORMONE, ENDOCRINOLOGY, HYPOTHAL-
	AMUS, FOLLICLE-STIMULATING HORMONE (FSH),
	ESTROGEN, GROWTH HORMONE-RELEASING FAC-
	TOR (GRF or GHRF), GROWTH HORMONE (GH).
	Plant Breeder’s Rights (PBR) The intellec-
	tual property rights that are legally accorded
	to plant breeders by various laws, interna-
	tional treaties, etc. Similar to patent law for
	inventors. See also PLANT’S NOVEL TRAIT
	(PNT), PLANT VARIETY PROTECTION ACT (PVP),
	PLANT PROTECTION ACT, EUROPEAN PATENT CON-
	VENTION, EUROPEAN PATENT OFFICE (EPO), U.S.
	PATENT AND TRADEMARK OFFICE (USPTO), UNION
	FOR PROTECTION OF NEW VARIETIES OF PLANTS
	(UPOV), COMMUNITY PLANT VARIETY OFFICE.
	Plant Hormone An organic compound syn-
	thesized in minute quantities by certain

© 2002 by CRC Press LLC