Using euhalophytes to understand salt tolerance and to develop saline agriculture: Suaeda salsa as a promising model

Background As important components in saline agriculture, halophytes can help to provide food for a growing world population. In addition to being potential crops in their own right, halophytes are also potential sources of salt-resistance genes that might help plant breeders and molecular biologists increase the salt tolerance of conventional crop plants. One especially promising halophyte is Suaeda salsa, a euhalophytic herb that occurs both on inland saline soils and in the intertidal zone. The species produces dimorphic seeds: black seeds are sensitive to salinity and remain dormant in light under high salt concentrations, while brown seeds can germinate under high salinity (e.g. 600 mm NaCl) regardless of light. Consequently, the species is useful for studying the mechanisms by which dimorphic seeds are adapted to saline environments. S. salsa has succulent leaves and is highly salt tolerant (e.g. its optimal NaCl concentration for growth is 200 mm). A series of S. salsa genes related to salt tolerance have been cloned and their functions tested: these include SsNHX1, SsHKT1, SsAPX, SsCAT1, SsP5CS and SsBADH. The species is economically important because its fresh branches have high value as a vegetable, and its seed oil is edible and rich in unsaturated fatty acids. Because it can remove salts and heavy metals from saline soils, S. salsa can also be used in the restoration of salinized or contaminated saline land.Scope Because of its economic and ecological value in saline agriculture, S. salsa is one of the most important halophytes in China. In this review, the value of S. salsa as a source of food, medicine and forage is discussed. Its uses in the restoration of salinized or contaminated land and as a source of salt-resistance genes are also considered.     

Flavonol glycosides from Chenopodium foliosum Asch

Three new flavonol glycosides, namely 6-methoxykaempferol-3-O-β-gentiobioside, gomphrenol-3-O-β-gentiobioside and gomphrenol-3-O-α-l-rhamnopyranosyl-(1 → 2)[β-d-glucopyranosyl-(1 → 6)]-β-d-glucopyranoside as well as the known patuletin-3-O-β-gentiobioside and spinacetin-3-O-β-gentiobioside were isolated from the aerial parts of Chenopodium foliosum Asch. The structures of the compounds were determined by means of spectroscopic methods (1D and 2D NMR, UV, IR, and HRMS). DPPH free radical scavenging activity of the new compounds was low or lacking.     

Shifting effects of physiological integration on performance of a clonal plant during submergence and de-submergence

Background and Aims

Submergence and de-submergence are common phenomena encountered by riparian plants due to water level fluctuations, but little is known about the role of physiological integration in clonal plants (resource sharing between interconnected ramets) in their adaptation to such events. Using Alternanthera philoxeroides (alligator weed) as an example, this study tested the hypotheses that physiological integration will improve growth and photosynthetic capacity of submerged ramets during submergence and will promote their recovery following de-submergence.

Methods

Connected clones of A. philoxeroides, each consisting of two ramet systems and a stolon internode connecting them, were grown under control (both ramet systems untreated), half-submerged (one ramet system submerged and the other not submerged), fully submerged (both ramet systems submerged), half-shaded (one ramet system shaded and the other not shaded) and full-shaded (both ramet systems shaded) conditions for 30 d and then de-submerged/de-shaded for 20 d. The submerged plants were also shaded to very low light intensities, mimicking typical conditions in turbid floodwater.

Key Results

After 30 d of submergence, connections between submerged and non-submerged ramets significantly increased growth and carbohydrate accumulation of the submerged ramets, but decreased the growth of the non-submerged ramets. After 20 d of de-submergence, connections did not significantly affect the growth of either de-submerged or non-submerged ramets, but de-submerged ramets had high soluble sugar concentrations, suggesting high metabolic activities. The shift from significant effects of integration on both submerged and non-submerged ramets during the submergence period to little effect during the de-submergence period was due to the quick recovery of growth and photosynthesis. The effects of physiological integration were not found to be any stronger under submergence/de-submergence than under shading/de-shading.

Conclusions

The results indicate that it is not just the beneficial effects of physiological integration that are crucial to the survival of riparian clonal plants during periods of submergence, but also the ability to recover growth and photosynthesis rapidly after de-submergence, which thus allows them to spread.     

The prehistoric use of Chenopodiaceae in Australia: Evidence from Carpenter's Gap shelter 1 in the Kimberley, Australia

The use of Chenopodiaceae and Amaranthaceae has been recorded in a rock shelter site that shows evidence of human occupation from 40,000 B.P. more or less continuously to the present. The plant remains are discussed in the light of ethnographic information for use of these taxa in both Australia and north America. The presence of cheno-ams as environmental indicators of aridity will be discussed.     

Effect of light and exogenously applied precursors on amaranthin synthesis in Amaranthus caudatus

Light stimulates the synthesis of amaranthin in Amaranthus caudatus var. viridis. Evidence suggests that this stimulation is markedly dependent on seedling age. Synthesis is controlled by both a “low-energy” red/far-red reversible phytochrome system and an HER at least partially under phytochrome control. In seedlings exposed to light, synthesis is promoted by exogenously applied DOPA and tyrosine. It is suggested that at least two light-promoted reactions occur in the biosynthetic pathway; one between tyrosine and DOPA and a second between DOPA and amaranthin.     

Diversification,evolution and methylation of short interspersed nuclear element families in sugar beet and related Amaranthaceae species

Short interspersed nuclear elements (SINEs) are non‐autonomous non‐long terminal repeat retrotransposons which are widely distributed in eukaryotic organisms. While SINEs have been intensively studied in animals, only limited information is available about plant SINEs. We analysed 22 SINE families from seven genomes of the Amaranthaceae family and identified 34 806 SINEs, including 19 549 full‐length copies. With the focus on sugar beet (Beta vulgaris), we performed a comparative analysis of the diversity, genomic and chromosomal organization and the methylation of SINEs to provide a detailed insight into the evolution and age of Amaranthaceae SINEs. The lengths of consensus sequences of SINEs range from 113 nucleotides (nt) up to 224 nt. The SINEs show dispersed distribution on all chromosomes but were found with higher incidence in subterminal euchromatic chromosome regions. The methylation of SINEs is increased compared with their flanking regions, and the strongest effect is visible for cytosines in the CHH context, indicating an involvement of asymmetric methylation in the silencing of SINEs.     

Demographic Analysis of a Disjunct Population of Froelichia floridana in the mid-Ohio River Valley

Froelichia floridana (cottonweed) occurs as a disjunct population along the Ohio River in southeastern Ohio. The anomalous occurrence of F. floridana in this area has led to its designation as a state endangered species and a management regime to maintain the habitat conditions in which it occurs. As part of this effort, a restoration site was established on public lands in 1984 from seed collected in areas threatened by development. This study seeks to determine the demographic characteristics of this species in the restored and non‐restored managed sites to provide basic ecological information regarding life history parameters and to judge the effectiveness of the restoration. For two years (1997–1998) we collected information on seed bank abundance, field seed germination, plant survivorship, and seed production to create a stage‐based transition matrix model. The model suggests that population growth and abundance as assayed by λ (rate of increase) are stable to declining and are similar between the restoration and natural sites. A reduction in competition had a positive effect on population growth. Elasticity analysis showed that plants germinating earlier in the spring and becoming established as an early cohort contributed a greater level of reproductive output than plants germinating in late spring. Lowered population growth for 1997 is attributed to a cooler and dryer than average early spring that delayed germination and subsequent seed production. Elasticity analysis also suggested that the presence of a persistent seed bank was crucial for long‐term population maintenance and may allow for recovery in areas of low aboveground abundance through soil manipulation.     

Hydroxylamine inhibition of the nitrate reductase complex from Amaranthus

Nitrate reductase from Amaranthus viridis is similar to nitrate reductase from other plant sources. NH₂OH inhibits nitrate reduction from NADH by the nitrate reductase complex, but it does not inhibit either the NADH-dehydrogenase activity or nitrate reduction from reduced flavin mononucleotides. The inhibition observed was non-competitive with nitrate when the enzyme was pre-incubated with NH₂OH and NADH, and competitive with nitrate without pre-incubation. The K_i values for NH₂OH were 5 μM and 30 μM with or without pre-incubation respectively.     

中国苋科一新分布

发表了作者在皖北植物资源调查中采集到的 1 5 0 0余号标本 ,经研究鉴定发现 ,中国苋科一新分布 ,阿尔维长序苋 (D .arvensisForsk .)文中所及标本 ,存安徽大学资源植物标本室。     

Ecdysteroids and a sucrose phenylpropanoid ester from Froelichia floridana

Phytoecdysteroid glycosides (1-5) and a phenylpropanoid ester of sucrose (6) were isolated from the whole plant of Froelichia floridana, along with eight known compounds including three ecdysteroids (7-9), four flavonoids (10-13), and one phenolic compound (14). Structures were determined using a combination of spectroscopic techniques. Compounds 1, 2 and 6-14 were tested in vitro for their activity against human DNA topoisomerase I. Compound 13 (diosmetin) showed marginal inhibition against topoisomerase I with IC₅₀ of 130 μM in conjunction with low intercalation ability.