Studies on the Alkaloids of Alseodaphne hainanensis Merr

Six alkaloids were isolated from the stem of Alseodaphne hainanensis Merr. (Lauraceae) collected in Hainan Island. Four of them were identified as xylopinine, armepavine, doryafranine, and 1-(4-methoxybenzyl)-6,7-methylenedioxy-l,2,3,4-tetrahydroisoquinoline by means of spectral analysis and comparison of physico-chemical constants.     

Photosynthetic properties of two different soybean suspension cultures

The photosynthetic properties of two commonly used suspension cultured lines, embryogenic and photoautotrophic (PA, SB-1 line) cells of soybean [Glycine max (L.) Merr.] were characterized. We found that compared to the dark green PA cells, the light green embryogenic cells contained fewer and smaller plastids with less-developed thylakoid membranes. The embryogenic cells also contained much lower contents of both chlorophyll and the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) protein, an undetectable level of Rubisco small subunit protein, and a very low rate of photosynthesis. While the DNA contents of the nuclear genomes were similar in these two types of cultured cells, the embryogenic cells possessed a markedly lower content of plastid DNA. The 18-year-old PA suspension culture, SB-1, continues to evolve with higher Rubisco and plastid DNA contents than leaves, and with small decreases in nuclear DNA content that appears to mimic changes in chromosome numbers. These findings may prove useful in the application of plastid transformation, particularly when non-leaf or non-green tissues must be used as targets for transformation and plant regeneration.     

星星草受精作用及其胚与胚乳早期发育的观察

利用常规石蜡切片法对星星草[Puccinellia tenuiflora(Griseb．)Scribn．et Merr．]受精过程及胚与胚乳的早期发育进行了观察,主要结论如下：(1)开花后2h,花粉管破坏1个助细胞,释放2个精子,精子呈逗点状。(2)开花后2～3h,2个精子分别移向卵细胞与极核。(3)开花后3～5h,精核分别贴附于卵细胞与极核的核膜上。(4)开花后5～10h,精核与卵核融合,雄性核仁出现,合子形成。(5)开花后5～6h,精核与极核融合,并出现雄性核仁,形成初生胚乳核,精核与极核的融合比与卵核融合要快。(6)开花后20h左右,合子分裂。(7)开花后8h,初生胚乳核。     

窄叶火筒树叶挥发油的化学成分分析

火筒树属（Leea L．）全世界约有70种,主产亚洲热带地区,中国分布有6种。火筒树属植物除了是很好的园艺和观赏植物外,许多种类可作药用,具有活血散瘀、愈溃生肌、清热解毒等功效,可用于治疗感冒发热、风湿痹痛、疮疡肿毒、咀嚼痛、跌打损伤、乳房肿痛、毒蛇咬伤,黄疸性肝炎等疾病。国内外对火筒树属植物的药理活性,特别是有关化学成分的研究报道很少。     

水分胁迫对长期UV—B辐射下柚树苗生理特性的影响

水分胁迫下,柚[Citrus maxima(Burm.)Merr.]树苗叶片相对含水量（RWC）、水势（ΨW)、净光合速率（Pn)、可溶性蛋白质和叶绿素（Chl)含量下降,丙二醛（MDA）、脯氨酸（Pro)含量和超氧化物歧化酶（SOD）活性升高,过氧化氢酶（CAT）活性先上升后下降,抗坏血酸过氧化物酶（APX）活性、抗坏血酸（AsA)和还原型谷胱甘肽（GSH）含量明显降低。叶绿素荧光参数中光系统Ⅱ光化学原初效率（Fv/Fm)、光系统Ⅱ电子传递量子效率（ΦPSⅡ）和光化学猝灭（qp)下降,非光化学猝灭（qN)和热能耗散系数（KD）升高。显示膜系统和PSⅡ是水分胁迫的主要抑制位点。抗旱性强的品种具有较高的活性氧清除能力。长期紫外线－B（UV－B）增强辐射能缓解水分胁迫下柚树苗叶片RWC、ΨW、APX活性和GSH、AsA含量下降,但对水分胁迫下的Pro含量、Pn和叶绿素荧光特性作用不明显。初步推测：UV－B和水分胁迫对植物有部分相同的作用机制,都导致植株膜脂过氧化程度加剧和PSⅡ的失活,同时存在各自作用方式的特异性。     

Temperature and growth-induced water potential

When the steins of dark-grown soybean [Glycine max (L.) Merr.] seedlings grew rapidly at favorable temperatures in saturating humidities, a water potential of about 0·2 MPa was induced by growth ($pS_o-$pS_w, where $pS_o is the water potential of the basal nonelongating tissue and $pS_w is the water potential of the elongating tissue). If this water potential was caused by high concentrations of solute in the apoplast, as has been proposed, lowering the temperature should have little effect on the potential. On the other hand, if the water potential was caused by apoplast tensions generated by growth, then the tensions should disappear as growth is inhibited by low temperatures. We observed that the growth-induced water potential became too small to detect when growth was inhibited by temperatures as low as 13—5 °C. The disappearance was observed as a rise in apoplast water potential using a thermocouple psychrometer for intact plants, a rise in cell turgor using a miniature pressure probe and a decrease in apoplast tensions using a pressure chamber. The disappearance was not caused by a loss of solute from the apoplast because the tensions fully accounted for the growth-induced water potential at all temperatures. The results are consistent with the lack of solute measured directly in the apoplast solutions at high temperatures (Nonami & Boyer 1987). Therefore, it was concluded that little solute was present in the apoplast at any temperature, and the growth-induced water potential was associated mostly with a tension that moved water from the xylem and into the surrounding cells to meet the demand of cell enlargement.     

Genetic control of high stearic acid content in seed oil of two soybean mutants

 Stearic acid is one of the two saturated fatty acids found in soybean [Glycine max (L.) Merr.] oil, with its content in the seed oil of commercial cultivars averaging 4.0%. Two mutants, KK-2 and M25 with two- and six-fold higher stearic acid contents in the seed oil than cv ‘Bay’, were identified after X-ray seed irradiation. Our objective was to determine the genetic control of high stearic acid content in these mutants. Reciprocal crosses were made between each mutant and ‘Bay’, and between the two mutants. No maternal effect for stearic acid content was observed from the analysis of F₁ seeds in any of the crosses. Low stearic acid content in ‘Bay’ was partially dominant to high stearic acid content in KK-2 and M25, and high stearic acid content in KK-2 was partially dominant to high stearic acid content in M25. Cytoplasmic effects were not observed, as demonstrated by the lack of reciprocal cross differences for stearic acid content in our analysis of F₂ seeds from F₁ plants. The stearic acid content in F₂ seeds of KK-2בBay’ and M25בBay’ crosses segregated into three phenotypic classes which satisfactorily fit a 1:2:1 ratio, indicating that high stearic acid content in KK-2 and M25 was controlled by recessive alleles at a single locus. The data for stearic acid content in F₂ seeds of the KK-2×M25 cross satisfactorily fit a 3:9:1:3 phenotypic ratio. The F₂ segregation ratio and the segregation of F₃ seeds from individual F₂ plants indicated that KK-2 and M25 have different alleles at different loci for stearic acid content. The alleles in KK-2 and M25 have been designated as st ₁ and st ₂, respectively. The stearic acid content (>30.0%) found in the st ₁ st ₁ st ₂ st ₂ genotype is the highest known to date in soybean, but it was not possible to develop the line with this genotype because the irregular seeds failed to grow into plants after germination. Therefore, tissue culture methods must be developed to perpetuate this genotype. Received: 28 March 1997 / Accepted: 18 April 1997     

Effect of Na/Ca and Na/K ratios in saline culture solution on the growth and mineral nutrition of rice (Oryza sativa L.)

Summary A study was conducted to evaluate the effect of manganese on accumulation of Zn, Fe, Cu, and B by different soybean genotypes under varying soil pH conditions, in view of determining tolerance towards extremes in soil pH and mineral toxicities. Enon sandy loam soil was used for the investigation in a greenhouse. Manganese rates were 0, 10, and 20 kg/ha. The pH levels were 5.3, 6.3, and 7.0. The soybean genotypes tested were PI 159319, PI 324924, PI 960895, and L-76-0132. Results indicate that Zn concentration in the genotypes leaf and seed was not affected by Mn application whereas the Cu concentration in the leaf was affected. In general, there was an increase in concentration of Fe in the genotypes seed with Mn application. Boron concentration in the genotypes leaf and seed was unaffected by Mn application. The effect of soil pH on Zn, Fe, Cu, and B in the genotypes tissue was significant. This did not result in toxic levels of the elements in the tissues.Contribution of the Department of Plant Science and Technology, North Carolina Agricultural and Technical State University, Greensboro, N.C. 27411, and Agronomic Division, North Carolina Department of Agriculture, Raleigh, NC 27611, USA