Yi Tang

Effect of culture conditions on the plant regeneration via organogenesis from cotyledonary node of cowpea ( Vigna unguiculata L. Walp)

A rapid and efficient regeneration system via organogenesis from cotyledonary node explants of cowpea (Vigna unguiculata L. Walp) has been established. The cotyledonary node explants excised from 4 days old seedlings, placed in vitro on medium containing salts of Murashige and Skoog and vitamins of Gamborg’s media (MSB 5 ). Adventitious shoots occurred at the basal end of the initiated axillary buds that preexisted at the node regions. BAP at 1.25 mg/l was the optimum for shoot induction. The combination of BAP with IBA had worthless effect on shoots proliferation. The number of adventitious buds was promoted when the seeds were preconditioned with appropriate concentrations of BAP (2 to 3 mg/l), whereas was depressed with higher concentrations of BAP (5 to 15 mg/l). The regeneration system was further optimized due to the presence of cotyledons attaching to the cotyledonary node explants. Explants with two entire cotyledons from 4 days old seedlings produced the greater number of shoots (7.83) after 3 weeks on MSB5 medium supplemented with 1.25 mg/l BAP. Regenerated shoots could well elongate on regulator-free basal medium and well root with 100% of success on the half strength medium supplemented with various concentrations of IBA (0, 0.1, 0.3, and 0.5 mg/l). The regenerated plantlets were cultured on the pots containing sterilized vermiculite and soil (1:1) with 27% of survival. Key words : Cowpea, plant regeneration, cotyledonary node, organogenesis.

Optimized system for plant regeneration of watermelon (Citrullus lanatus Thumb.)

The objective of this study was to establish an efficient and reproducible in vitro plant regeneration for Citrullus lanatus cv. Zaojia. To achieve optimal conditions for adventitious shoot induction, five explants (entire cotyledons, distal cotyledons, proximal cotyledons, cotyledonary node A and cotyledonary node B) were tested on MS medium supplemented with different concentrations and combinations of growth regulators (0 to 0.2 mg/L IAA and 1.0 to 5.0 mg/L BA), the results showed that entire cotyledons cultured in MS + BA (2.0mg/L) + IAA(0.2mg/L) achieved the highest regenerated rate (89.67%) and the optimal protocol screened in this experiment had 7.69 ± 0.10 shoots per explants. Adventitious shoots were able to elongate both on MS medium with 0.2 mg/L KT and 0.2 mg/L NAA; IBA 0.3mg/L was found to be effective in the production of root. Acclimatized plantlets transferred to pot resumed growth, and their stems and leaves elongated and expanded in one month. Key words: Watermelon (Citrullus lanatus Thumb.), optimized system, regeneration, cotyledon explants, cotyledonary node.

In vitro induction of multiple buds from cotyledonary nodes of Balsam pear (Momordica charantia L.)

In this study, cotyledonary nodes of Changbai, Dabai and Youlv Balsam pear (Momordica charantia L.) were used for tissue culture to establish regeneration system, and the effects of different genotypes of Balsam pear, hormone combinations, seedling ages, dark period and AgNO3 concentrations on the bud regeneration were compared. The results show that eight-day old seedling was the best for multiple buds regeneration. The combination of 6-benzylaminopurine (6-BA) and indole-3-butyric acid (IBA) had the best effect on the induction of multiple buds. The optimum medium for the induction of multiple buds in Balsam pear was Murashige and Skoog (MS) medium supplemented with 2.5 mgL -1 of 6-BA and 0.1 mgL -1 of IBA. Inducing frequency varied with the genotypes, of which Changbai showed highest percentage of induction. One week dark treatment could increase the rate of shoot regeneration from 76.91 to 80.91%. The addition of AgNO3 which varied from 1 to 6 mg L -1 in the medium could not help to

Melatonin Improves Heat Tolerance in Kiwifruit Seedlings through Promoting Antioxidant Enzymatic Activity and Glutathione S-Transferase Transcription

Evidence exists to suggest that melatonin (MT) is important to abiotic stress tolerance in plants. Here, we investigated whether exogenous MT reduces heat damage on biological parameters and gene expression in kiwifruit (Actinidia deliciosa) seedlings. Pretreatment with MT alleviates heat-induced oxidative harm through reducing H2O2 content and increasing proline content. Moreover, MT application raised ascorbic acid (AsA) levels and the activity of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). We also observed elevation in the activity of enzymes related to the AsA-GSH cycle, such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR). Furthermore, MT application increased the expression of 28/31 glutathione S-transferase (GST) genes, reducing oxidative stress. These results clearly indicate that in kiwifruit, MT exerts a protective effect against heat-related damage through regulating antioxidant pathways.

The influence of endogenous hormones on the formation of buds from stems of bitter melon ( Momordıca charantıa L.)

Stems of bitter melon ( Momordica charantia L.) cv. Dabai were used to establish in vitro cultures. The endogenous hormone concentrations (indoleacetic acid [IAA], abscisic acid [ABA], gibberellins 3 [GA 3], zeatin [ZT]) of the calluses were determined by means of high pressure liquid chromatography (HPLC). The endogenous ZT was higher in the stem calluses that had formed buds, and there was a higher IAA/ZT ratio and GA 3/ZT ratio in the calluses having no capacity for buds formation. The results showed that addition of plant growth regulator influences endogenous hormone status and it will be helpful for in vitro propagation of bitter melon.

Effects of living hyperaccumulator plants and their straws on the growth and cadmium accumulation of Cyphomandra betacea seedlings

To determine whether the living hyperaccumulator plants and their straws have the same effects on the growth and heavy metal accumulation of common plants, two pot experiments (intercropping experiment and straw mulch experiment) were conducted to study the effects of living hyperaccumulator plants (Solanum photeinocarpum, Tagetes erecta, Galinsoga parviflora and Bidens pilosa) and their straws on the growth and cadmium (Cd) accumulation of common plant Cyphomandra betacea seedlings. Intercropping with T. erecta or B. pilosa promoted the growth of C. betacea seedlings compared with the monoculture, while intercropping with S. photeinocarpum or G. parviflora inhibited that. Intercropping with S. photeinocarpum decreased the Cd contents in the roots and shoots of C. betacea seedlings compared with the monoculture, but intercropping with the other plants did not. In the straw mulch experiment, the straw of S. photeinocarpum or T. erecta promoted the growth of C. betacea seedlings compared with the control, while the straw of G. parviflora or B. pilosa did not. The straw of S. photeinocarpum or T. erecta decreased the Cd contents in the shoots of C. betacea seedlings, and the straw of G. parviflora or B. pilosa increased the shoot Cd contents. Thus, intercropping with S. photeinocarpum and applying S. photeinocarpum or T. erecta straw can reduce the Cd uptake of C. betacea.

Hyperaccumulator straw improves the cadmium phytoextraction efficiency of emergent plant Nasturtium officinale

With the development of economy, the heavy metal contamination has become an increasingly serious problem, especially the cadmium (Cd) contamination. The emergent plant Nasturtium officinale R. Br. is a Cd-accumulator with low phytoremediation ability. To improve Cd phytoextraction efficiency of N. officinale, the straw from Cd-hyperaccumulator plants Youngia erythrocarpa, Galinsoga parviflora, Siegesbeckia orientalis, and Bidens pilosa was applied to Cd-contaminated soil and N. officinale was then planted; the study assessed the effect of hyperaccumulator straw on the growth and Cd accumulation of N. officinale. The results showed that application of hyperaccumulator species straws increased the biomass and photosynthetic pigment content and reduced the root/shoot ratio of N. officinale. All straw treatments significantly increased Cd content in roots, but significantly decreased Cd content in shoots of N. officinale. Applying hyperaccumulator straw significantly increased the total Cd accumulation in the roots, shoots, and whole plants of N. officinale. Therefore, application of straw from four hyperaccumulator species promoted the growth of N. officinale and improved the phytoextraction efficiency of N. officinale in Cd-contaminated paddy field soil; the straw of Y. erythrocarpa provided the most improvement.

Effects of grafting on the cadmium accumulation characteristics of the potential Cd-hyperaccumulator Solanum photeinocarpum

The effects of grafting on the cadmium (Cd) accumulation characteristics of the potential Cd-hyperaccumulator Solanum photeinocarpum were studied under Cd stress in our experiment. Four treatments were used in the experiment: ungrafted (UG), self-rooted grafting by the same S. photeinocarpum seedling (SG), self-rooted grafting by two different development stages of S. photeinocarpum seedlings (DG), and grafting on the rootstock of wild potato (PG). SG and DG decreased the root, scion stem, leaf, whole shoot, and whole plant biomasses compared with UG, but increased the rootstock stem biomass, while only PG increased the root and whole plant biomasses. SG and DG increased the Cd contents in the different organs of S. photeinocarpum compared with UG, while PG decreased the Cd content compared with UG. The Cd extraction by the whole plant of S. photeinocarpum was ranked as DG > SG > UG > PG. Additionally, the antioxidant enzyme activities in SG and DG were enhanced compared with UG, while that of PG was reduced compared with UG. The grafting increased the DNA methylation levels and changed the methylation patterns of S. photeinocarpum compared with UG. Therefore, SG and DG can increase the Cd accumulation in S. photeinocarpum, which can be used for the phytoremediation of Cd-contaminated soil.

Agrobacterium-mediated transformation of watermelon (Citrullus lanatus)

Transformation of watermelon (Citrullus lanatus cv. Zaojia) using Agrobacterium tumefaciens strain EHA105 containing the plasmid pRD400 carrying Pti4 gene was studied in this work. Proximal cotyledons as explants were pre-cultivated for two day in the dark and it was found that the best condition for transformation of watermelon was the use of bacteria at a concentration of OD600 0.3, inoculation for 10 min and 72 h of co-cultivation. Kanamycin as a selective agent in different concentration (75, 100 and 125 mg/l) was tested. Transformed explants on medium supplemented with 100 mg/l kanamycin received a higher efficiency of shoots with transgenic DNA (9.17%). Using specific primer to Pti4 gene, PCR product with a size of 680 bp was amplified when the genomic DNA extracted from the transformants were used as templates. A total of 148 plants with percentage 10.28% showed positive results using PCR analysis and subsequently all were regenerated into whole plants.

Melatonin affects the growth and cadmium accumulation of Malachium aquaticum and Galinsoga parviflora

ABSTRACT Phytoremediation technology has become one of the main techniques for remediating soils polluted by heavy metals because it does not damage the environment, but heavy metal-tolerant plants have the disadvantages of low biomass and slow growth. A pot experiment was conducted to study the effects of melatonin (Mel) on growth and cadmium (Cd) accumulation in the Cd accumulator Malachium aquaticum and hyperaccumulator Galinsoga parviflora by spraying different concentrations of Mel on them. The results showed that shoot biomass, photosynthetic pigment content and antioxidant enzyme activity were increased in both species after Mel was sprayed on their leaves. Mel reduced the Cd content in shoots of M. aquaticum and increased it in those of G. parviflora. In general, Cd accumulation was greatest in M. aquaticum when Mel was 200 μmol L−1 (120.71 μg plant−1, increased by 15.97% than control) and in G. parviflora when Mel was 100 μmol L−1 (132.40 μg plant−1, increased by 68.30% than control). Our results suggest it is feasible to improve the remediation efficiency of lightly Cd-contaminated soil by spraying G. parviflora with100 μmol L−1 Mel.