Pimchai Apavatjrut

A study of low-energy ion beam effects on outer plant cell structure for exogenous macromolecule transferring

Abstract The aim of this study was to investigate low-energy ion beam effects on inducing exogenous macromolecule transfer through cell walls into cells and the related dependence. The experiment focused on 20–30 keV Ar ion implantation in various plant tissues to doses ranging from 1014 to 1016 ions/cm2. Auxiliary 15–30 keV N ion implantation in the plant tissues as well as 25 keV Ar ion implantation in bacteria of E. coli was also carried out. The effects of ion beam bombardment on the outer cell structure and the ability of transferring large exogenous molecules of Trypan blue (TB) and plasmid DNA were investigated. Typical results show that the 20 keV Ar ion implantation only leads to retaining of the TB dye in the cell wall whereas the 30 keV Ar ion implantation can allow the dye to enter the cell. A discussion based on simulations of the ion implantation processes indicates that the cell wall composed of cellulose microfibrils is in a porous structure so that ions at certain low energies with appropriate doses can increase permeability of the cell wall and induce exogenous macromolecule transferring.

Ion penetration depth in the plant cell wall

Abstract This study investigates the depth of ion penetration in plant cell wall material. Based on the biological structure of the plant cell wall, a physical model is proposed which assumes that the wall is composed of randomly orientated layers of cylindrical microfibrils made from cellulose molecules of C6H12O6. With this model, we have determined numerical factors for ion implantation in the plant cell wall to correct values calculated from conventional ion implantation programs. Using these correction factors, it is possible to apply common ion implantation programs to estimate the ion penetration depth in the cell for bioengineering purposes. These estimates are compared with measured data from experiments and good agreement is achieved.

Characteristics of heavy ion beam-bombarded bacteria E. coli and induced direct DNA transfer

Abstract The goal of the work described here was to study ion beam interactions with bacteria and thus develop an understanding of the mechanisms involved in ion bombardment-induced direct gene transfer into bacterial cells. Ar ion beams at an energy of 26 keV and fluences ranging from 5×10 14 to 4×10 15 ions/cm 2 were used to bombard bacterial cells of Escherichia coli strain DH5α. The bacteria were able to survive the low-temperature and low-pressure treatment conditions for at least a few hours. The ion bombardment created novel crater-like structures on the surface of the bacterial cell envelope, as observed by scanning electron microscopy. Four variously sized DNA plasmids carrying the ampicillin resistance gene were transferred and expressed in E. coli cells bombarded with ion fluences of 1×10 15 and 2×10 15 ions/cm 2 . The dependence of the DNA transfer on the plasmid DNA size, ion fluence and incubation time all suggests that the ion beam-induced surface crater-like structures provide the pathway for the mechanism that is responsible for the ion beam-induced DNA transfer.

Some investigations of ion bombardment effects on plant cell wall surfaces

Abstract Recent developments in the field of ion beam bioengineering, for example our own work demonstrating ion beam-induced transfer of exogenous macromolecules into the interior cell region, have underscored the need for a better understanding of the effects of ion bombardment on the cell wall material. We describe here, our investigations of ion beam sputtering of plant cell wall material and ion beam-induced damage to the cell wall. The presently available ion implantation simulation programs are not adequate, and experimental results are not available, either. We have indirectly estimated the surface sputtering yield of plant cell wall composed of C6H12O6-compound by remodeling the cell wall material so as to use partial mass densities and surface binding energies in the available ion implantation programs. For bombardment with a 30-keV Ar-ion beam, the sputtering yield from the cell wall is estimated to be approximately 10 atoms/ion, which is somewhat greater than the value predicted by direct program simulation, but in good agreement with experimental results. We have also performed electron microscopy on the ion-bombarded cell walls. The micrographs show novel microcrater-like structures on the cell wall subsequent to ion bombardment, which could be the ion beam-generated pathways for exogenous macromolecule transfer.

Changes in nitrogenous compounds, carbohydrates and abscisic acid in Curcuma alismatifolia Gagnep. during dormancy

Summary Stubbed rhizomes of Curcuma alismatifolia Gagnep. were kept at room temperature with good ventilation during their dormant period and then were randomly sampled at different stages of dormancy, i.e. stage 1 (beginning of dormancy), stage 2 (middle of dormancy) and stage 3 (late in dormancy with the buds sprouting). Fresh and dry weights, water content, nitrogencontent and starch and total soluble sugar content decreased in the stubbed rhizome and storage roots during dormancy. Therhizome was the principal organ for N storage and the storage roots were the major organ for carbohydrate storage. Argin ne and glutamic acid were the predominant free amino acids in the rhizome and storage roots, respectively. Free abscisic acid in the rhizome increased from stage 1 to 2 and then decreased by stage 3, while the concentration in storage roots decreased continuously until buds sprouted.

Effect of nitrogen supply on nitrogen and carbohydrate constituent accumulation in rhizomes and storage roots of Curcuma alismatifolia Gagnep.

Abstract Curcuma (Curcuma alismatifolia cv. Gagnep.), a tropical flowering plant known as “Siam tulip”, were cultivated in a pot with vermiculite and supplied with different levels of nitrogen (N). Rhizomes with storage roots were harvested at 215 days after planting. Results indicated that a high level of N supply increased flower numbers and promoted continuous new rhizome formation, but storage root growth was depressed. The N supply to the plants increased the N concentrations both in the rhizomes and in the storage roots. The predominant nitrogenous compounds related to total N increase were proteins in the rhizomes. The N of the insoluble fraction of 80% ethanol or the N of the soluble fraction of 10% trichloroacetic acid was the predominant fraction of N that accumulated in the storage roots. A lack of N supply increased the starch concentration both in the rhizomes and in the storage roots. These results suggested that a high level of N supply to the curcuma plant increased new rhizome formation because of increased flower numbers, but depressed new storage root formation because of reduced starch accumulation.

Evaluation of Curcuma as potted plants and cut flowers

Summary Sixteen accessions of Curcuma germplasm that included C. alismatifolia ‘Chiang Mai Pink’, and ‘Lady Di’ and C. thorelii ‘Chiang Mai Snow’ and C. alismatifolia ‘Pink’, C. parviflora ‘White Angel’, and C. sp. ‘CMU Pride’ were evaluated for use as potted plants or as cut flowers. All cultivars of C. alismatifolia and C. thorelii ‘Chiang Mai Snow’ were considered suitable for cut-flower and pot-plant use, respectively. C. parviflora ‘White Angel’ also proved to be a suitable cultivar for potted plant production. Optimum storage temperatures for rhizomes in relation to greenhouse forcing and ethanol-soluble glucose, fructose and sucrose concentrations were determined. Storing rhizomes at 25° – 30°C for 2 – 3 months after harvest is recommended to break dormancy. Plants of C. parviflora ‘White Angel’ flowered 50 – 89 d after potting and can be used as potted plants. Plants of C. alismatifolia flowered 96 – 133 d after potting, with floral stem-lengths suitable as cut flowers. High levels of boron or manganese were correlated with burn symptoms at the margins of the leaves [‘leaf-margin burn’ (‘LMB’)] and were observed in old leaves of ‘CMU Pride’ at flowering. Levels of ethanol-soluble fructose, glucose and sucrose in the tuberous roots of Curcuma were higher than the levels in rhizomes, and increased as storage temperatures increased. Accelerated leaf emergence from rhizomes stored at 30°C took 16 d and was associated with increases in glucose and fructose contents. Very similar morphological characters between C. thorelii ‘Chiang Mai Snow’ and C. parviflora ‘White Angel’ emphasised that identification of Curcuma accessions using DNA-markers is required for future studies.