In Vitro Regeneration of Endangered Medicinal Plant Heliotropium kotschyi (Ramram).

Heliotropium kotschyi (Ramram) is an important endangered medicinal plant distributed in the Kingdom of Bahrain. Plant tissue culture technique is applied for ex situ conservation study. Nodal stem segments are cultured in modified MS media supplemented with various combination and concentration of plant growth regulators (PGRs). Plants are regenerated via shoot organogenesis from the nodal meristems. Plants are regenerated in three different steps: initial shoot development, shoot multiplication, and rooting. After 4 weeks of culture, 100 % explants respond to shoot initiation on the medium containing 8.88 µM BAP and 5.71 µM IAA. The highest frequency of shoot regeneration is observed in the same media after second subculture of shoots. The highest rooting frequency is observed in the presence of 2.85 µM IAA. After root development, the plantlets are transferred to pots filled with soil and 60 % of plants survived after 45 days. This plant regeneration protocol is of great value for rapid desert plant propagation program.

Polyamines in response to abiotic stress tolerance through transgenic approaches.

The distribution, growth, development and productivity of crop plants are greatly affected by various abiotic stresses. Worldwide, sustainable crop productivity is facing major challenges caused by abiotic stresses by reducing the potential yield in crop plants by as much as 70%. Plants can generally adapt to one or more environmental stresses to some extent. Physiological and molecular studies at transcriptional, translational, and transgenic plant levels have shown the pronounced involvement of naturally occurring plant polyamines (PAs), in controlling, conferring, and modulating abiotic stress tolerance in plants. PAs are small, low molecular weight, non-protein polycations at physiological pH, that are present in all living organisms, and that have strong binding capacity to negatively charged DNA, RNA, and different protein molecules. They play an important role in plant growth and development by controlling the cell cycle, acting as cell signaling molecules in modulating plant tolerance to a variety of abiotic stresses. The commonly known PAs, putrescine, spermidine, and spermine tend to accumulate together accompanied by an increase in the activities of their biosynthetic enzymes under a range of environmental stresses. PAs help plants to combat stresses either directly or by mediating a signal transduction pathway, as shown by molecular cloning and expression studies of PA biosynthesis-related genes, knowledge of the functions of PAs, as demonstrated by developmental studies, and through the analysis of transgenic plants carrying PA genes. This review highlights how PAs in higher plants act during environmental stress and how transgenic strategies have improved our understanding of the molecular mechanisms at play.