Induction of larval metamorphosis in the sea cucumber Apostichopus japonicus by neurotransmitters

Larval metamorphosis inducers of the sea cucumber Apostichopus japonicus were screened from physiologically active compounds. Doliolaria larvae completed their metamorphosis to juveniles in 120 h when treated with 5–10 μM of dopamine and l-DOPA, and 50 μM of l-adrenaline and l-noradrenaline. Doliolaria larvae had to be exposed to dopamine or l-DOPA for at least 24 h. D1-like dopamine receptor antagonists SKF87566 and LE300 (10 μM) inhibited metamorphosis by dopamine. However, the D2-like dopamine receptor antagonists sulpiride and nemonapride (10 μM) did not inhibit the effect of dopamine. The results suggest that D1-like dopamine receptors are involved in larval metamorphosis of the sea cucumber A. japonicus.     

Effects of elevated CO2 concentration on growth, annual ring structure and photosynthesis in Larix kaempferi seedlings

We evaluated the effects of elevated carbon dioxide concentration ([CO2]) and two nutrient regimes on stem growth rate, annual ring structure and temporal variations in photosynthetic characteristics of seedlings of Japanese larch (Larix kaempferi (Lamb.) Carr.). Seedlings were grown in phytotron chambers in an ambient (360 ppm) or an elevated (720 ppm) [CO2] in two nutrient regimes for one growing season. Elevated [CO2] reduced stem height and increased stem basal diameter compared with ambient [CO2]. The effect of elevated [CO2] on growth tended to be greater at high-nutrient supply than at low-nutrient supply. Elevated [CO2] had no significant effect on ring width or the number of tracheids per radial file. There was no obvious difference in cell wall thickness or the relative area of the cell wall between seedlings grown in ambient or elevated [CO2]. Although growth in elevated [CO2] resulted in a slight increase in cell diameter, the increase had a relatively minor effect on the relative area of the cell wall. Net assimilation rate increased in response to elevated [CO2]; however, the increase in whole-crown photosynthetic rate (Total Agrowth) in seedlings in the elevated [CO2] treatment was minimal because of the smaller specific needle area and acclimation of the photosynthetic characteristics of the needles to the growth [CO2]. In conclusion, we observed no obvious enhancement in the capacity for carbon fixation in Japanese larch seedlings grown in the presence of elevated [CO2] that might be attributable to changes in stem growth. However, elevated [CO2] caused changes in the temporal pattern of stem growth and in some anatomical features of the tracheids.     

Growth and annual ring structure of Larix sibirica grown at different carbon dioxide concentrations and nutrient supply rates

We compared effects of ambient (360 vpm) and elevated (720 vpm) carbon dioxide concentration ([CO2]) and high and low nutrient supply rates on stem growth, annual ring structure and tracheid anatomy of Siberian larch (Larix sibirica Ledeb.) seedlings over two growing seasons. Elevated [CO2] had no significant effect on either stem height or diameter growth; however, both stem height and diameter growth were enhanced by the high nutrient supply rate, and these increases were stimulated by elevated [CO2]. Elevated [CO2] tended to increase the width of the annual xylem ring, the number of cells in a radial file spanning the ring, and tracheid lumen diameter, whereas it tended to reduce cell wall thickness, although there were no statistically significant CO2 effects on tracheid anatomy. Changes in tracheid cell morphology seemed to be dependent on changes in shoot elongation rates.     

Tolerance of Japanese larch to drought is modified by nitrogen and water regimes during cultivation of container seedlings

Improving drought tolerance of container seedlings of Japanese larch is of high importance to afforestation. We hypothesized that adequate nitrogen (N) and limited water supply would increase the tolerance of container seedlings to water-deficit stress, circumventing photoinhibition, by means of (i) enhanced photosynthetic capacity with higher leaf N and (ii) decreased water loss from leaves with lower biomass allocation into aboveground parts. Container seedlings of Japanese larch were grown under the treatment combinations of adequate (+?N: 300 mg N container^?1) or limited (??N: 150 mg N container^?1) N and adequate (+?W: daily irrigation) or limited (??W: twice-a-week irrigation) water. Then, seedlings were subjected to a progressive drought treatment. Higher leaf N was observed in container seedlings grown under?+?N and???W. During progressive drought, lower stomatal conductance and net photosynthetic rate were observed in leaves with higher leaf N at a given predawn leaf water potential. Furthermore, the maximum efficiency of PSII photochemistry (F_v/F_m) was lower in leaves with higher leaf N, suggesting that higher leaf N might impair intrinsic tolerance to drought at the leaf level contrary to expectations. Conversely,???N and???W seedlings with lower shoot biomass delayed soil drying as a whole-plant response via a reduction in leaf transpiration, leading to delayed photoinhibition as indicated by a decline in F_v/F_m. To circumvent stress at the initial stage of water deficit, lower leaf N via limited N regime and smaller shoot biomass driven by limited N and water regimes would be important.

     

Fractionation method for the determination of the root length of field-grown wheat

Abstract

Extract

Studies on the root system which are essential to understand the nutrient and water uptake by plant, are very difficult because the root system in the soil can not be observed directly unlike the shoot system. Even basic parameters, such as root length and root surface area cannot be measured easily.     

Upregulation of the genes for ferritin,RNase, and DnaJ in leaves of rice plants in response to sulfur deficiency

Microarray analysis was carried out with mRNAs isolated from aerial portions of rice plants subjected to sulfur deficiency. Among the candidate clones regulated by sulfur deficiency, three genes were identified by northern analysis that showed altered levels of mRNA accumulation. Genes similar to those for ferritin, S-like ribonuclease, and DnaJ-like protein were down-, down-, and upregulated by sulfate deficiency, respectively. These genes were found for the first time to be responsive to sulfur nutrition in the present study.     

QTLs for Sugar Content of Stalk in Sweet Sorghum （Sorghum bicolor L.Moench）

High sugar content of sorghum stalk is an important factor in the sorghum silage production. To identify the genomic regions controlling sugar content and to develop molecular markers linked to sugar content in sweet sorghum, we used an F2：3 segregating population consisting of 207 individuals derived from a cross between a high sugar content inbred line, Early Folger, and a normal inbred line, N32B, for genetic linkage mapping and quantitative trait locus （QTL） analysis. We constructed a genetic linkage map spanning 983.5 cM based on a total of 327 markers comprising 31 restriction fragment length polymorphism （RFLP） markers, 254 amplified fragment length polymorphism （AFLP） markers, and 42 simple sequence repeat （SSR） markers. In the 20 linkage groups detected, 98.2% of markers aligned to the 10 linkage groups of sorghum. Variations in sugar content at different growth stages and among internodes suggested that the sugar content of middle internodes is stable and suitable for measuring at early dough stage. The broad sense heritability （hB0 of sugar content was 0.64 and 0.62 estimated from the data of F3 families and each parent in 2003 and 2004. We identified one and two QTLs accounting for 22.2 to 25.0% of phenotypic variance using simple interval mapping method in 2003 and 2004, respectively. These two QTLs showed a negative additive effect, and over-dominance effect. A QTL on LG-D was detected in both two years. Above results will be help us to understand the genetic mechanism of sugar content in sorghum and the QTL detected in this study might be useful in the improvement of sugar content by marker-assisted selection.     

QTLs for Sugar Content of Stalk in Sweet Sorghum (Sorghum bicolor L.Moench)

High sugar content of sorghum stalk is an important factor in the sorghum silage production. To identify the genomic regions controlling sugar content and to develop molecular markers linked to sugar content in sweet sorghum, we used an Early Folger, and a normal inbred line, N32B, for genetic linkage mapping and quantitative trait locus (QTL) analysis. We constructed a genetic linkage map spanning 983.5 cM based on a total of 327 markers comprising 31 restriction fragment length polymorphism (RFLP) markers, 254 amplified fragment length polymorphism (AFLP) markers, and 42 simple sequence repeat (SSR) markers. In the 20 linkage groups detected, 98.2% of markers aligned to the 10 linkage groups of sorghum.Variations in sugar content at different growth stages and among internodes suggested that the sugar content of middle internodes is stable and suitable for measuring at early dough stage. The broad sense heritability (hB2) of sugar content was 0.64 and 0.62 estimated from the data of F3 families and each parent in 2003 and 2004. We identified one and two QTLs accounting for 22.2 to 25.0% of phenotypic variance using simple interval mapping method in 2003 and 2004, respectively.These two QTLs showed a negative additive effect, and over-dominance effect. A QTL on LG-D was detected in both two years. Above results will be help us to understand the genetic mechanism of sugar content in sorghum and the QTL detected in this study might be useful in the improvement of sugar content by marker-assisted selection.