Isolation and identification of PNP-A homologues from Xerophyta viscosa Baker
Maintenance of growth, development and normal physiological processes remains crucial for the survival of plants. Plant hormones are described as integrators of external signal and internal developmental process in plants. They also attribute as mediators of physiological and developmental adaptation throughout the plant life cycle (Wilkinson et al.,1997). It has been well over 50 years since Went and Thimann (1937) published their classical book Phytohorrnones. At that time, the term phytohorrnone was synonymous to auxin, although compounds like cell division factors were anticipated to be phytohormones based on physiological experiments. Since then a number of plant hormones were discovered and a series of studies concluded that plant hormones are at least partly responsible for plant growth, development, cell elongation, cell division, differentiation and stomatal movement in response to environmental stimuli. Plant hormones are categorized into three groups, known as classical, non-classical and peptide hormones. Here, Plant Natriuretic Peptide (PNP) will be reviewed as a proposed additional peptide hormone.