Production of the phytohormone indole-3-acetic acid (IAA) is widespread among bacteria that inhabit the rhizosphere of plants. Several different IAA biosynthesis pathways are used by these bacteria, with a single bacterial strain sometimes containing more than one pathway. The level of expression of IAA depends on the biosynthesis pathway; the location of the genes involved, either on chromosomal or plasmid DNA, and their regulatory sequences; and the presence of enzymes that can convert active, free IAA into an inactive, conjugated form. The role of bacterial IAA in the stimulation of plant growth and phytopathogenesis is considered.

Bacterial biosynthesis of indole-3-acetic acid

1-Methylcyclopropene: a review

Because of their ability to transform atmospheric N2 into ammonia that can be used by the plant, researchers were originally very optimistic about the potential of associative diazotrophic bacteria to promote the growth of many cereals and grasses. However, multiple inoculation experiments during recent decades failed to show a substantial contribution of Biological Nitrogen Fixation (BNF) to plant growth in most cases. It is now clear that associative diazotrophs exert their positive effects on plant growth directly or indirectly through (a combination of) different mechanisms. Apart from fixing N2, diazotrophs can affect plant growth directly by the synthesis of phytohormones and vitamins, inhibition of plant ethylene synthesis, improved nutrient uptake, enhanced stress resistance, solubilization of inorganic phosphate and mineralization of organic phosphate. Indirectly, diazotrophs are able to decrease or prevent the deleterious effects of pathogenic microorganisms, mostly through the synthesis of anti...

Plant Growth-Promoting Effects of Diazotrophs in the Rhizosphere

The use of 1-methylcyclopropene (1-MCP) on fruits and vegetables.

Increased and accelerated global economic activities over the past century have led to interlinked problems that require urgent attention. The current patterns of production and consumption have raised serious concerns. In this context, greater emphasis has been put on the concept of sustainable economic systems that rely on technologies based on and supporting renewable sources of energy and materials. Average UK households produce around 3.2 million tonnes of packaging waste annually whereas 150 million tonnes of packaging waste is generated annually by industries in the UK. Hence, the development of biologically derived biodegradable polymers is one important element of the new economic development. Key among the biodegradable biopolymers is a class known as polyhydroxyalkanoates. Polyhydroxyalkanoates (PHAs) are a family of polyhydroxyesters of 3-, 4-, 5- and 6-hydroxyalkanoic acids, produced by a variety of bacterial species under nutrient-limiting conditions with excess carbon. These water-insoluble storage polymers are biodegradable, exhibit thermoplastic properties and can be produced from renewable carbon sources. Thus, there has been considerable interest in the commercial exploitation of these biodegradable polyesters. In this review various applications of polyhydroxyalkanoates are discussed, covering areas such as medicine, agriculture, tissue engineering, nanocomposites, polymer blends and chiral synthesis. Overall this review shows that polyhydroxyalkanoates are a promising class of new emerging biopolymers.

Polyhydroxyalkanoates: biodegradable polymers with a range of applications

Prestorage hot water treatments (immersion, rinsing and brushing)

GRAS, plant- and animal-derived compounds as alternatives to conventional fungicides for the control of postharvest diseases of fresh horticultural produce

A unique rapid hot water treatment to improve storage quality of sweet pepper

Inoculation of maize seedlings with 107 colony forming units (cfu) of Azospirillum plant−1 significantly increased the root surface area 2 weeks after sowing as compared to non-inoculated plants. Indole-3-acetic acid (IAA) was identified by gas liquid chromotography (GLC) and gas chromatography-mass spectrometry (GC-MS) in Azospirillum tryptophan-free culture medium. The amount of IAA in the medium was calculated from the gas chromatogram by isotope dilution analysis and found to be 32–40 ng ml−1. Roots of Azospirillum-inoculated maize seedlings were found to have higher amounts of both free and bound IAA as compared to control. The amount of free IAA significantly increased in the inoculated roots 2 weeks after sowing. IAA and indole-3-butyric acid (IBA) were identified by GC-MS only in the roots of Azospirillum-inoculated seedlings 2 weeks after sowing. The significance of the higher amounts of IAA following inoculation with the bacteria is discussed.

Elazar Fallik

Papers

Prestorage hot water treatments (immersion, rinsing and brushing)

GRAS, plant- and animal-derived compounds as alternatives to conventional fungicides for the control of postharvest diseases of fresh horticultural produce

A unique rapid hot water treatment to improve storage quality of sweet pepper

Identification and quantification of IAA and IBA in Azospirillum brasilense-inoculated maize roots

Light quality manipulation improves vegetable quality at harvest and postharvest: A review