Provenance- and subculture-dependent variation during micropropagation of Gmelina arborea

Axillary shoot elongation, formation of multiple shoots and rooting of shoots were compared in nodal segment cultures of Gmelina arborea Roxb. from seedlings obtained from six provenances, over several subcultures. Provenance-dependent variation was observed with respect to these parameters. In addition, a subculture-dependent decrease was observed in multiple shoot formation and root induction. Seventy percent of the rooted plantlets were successfully hardened and transferred to soil. A transient decrease in photochemical efficiency was observed during the early stages of hardening, whereas ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) levels increased gradually as the plants acclimatized to photoautotrophic growth.     

Analysis of photosynthetic productivity of microalgal mass cultures

The calculated value of microalgal massproductivity is an important parameter incommercial mass production and derivativecompound production. Mathematical analysiswas conducted in order to predict the rateof microalgal mass production, which wascalculated from the factor of oxygenevolution rate and the respiration rate percell. Calculated productivities of twomutants with small light-harvestingpigment, a phycocyanin deficient mutant ofSynechocystis PCC 6714 (strain PD-1)and a mutant with small light-harvestingpigment of Chlamydomonasperigranulata (strain LHC-1), wereevaluated compared with the wild-types ofthese mutants, respectively. The resultsshow that calculated productivity isimproved by reducing the content oflight-harvesting pigment, which issupported by the actual values ofphotosynthetic productivity. Productiveimprovement by reducing the content oflight-harvesting pigment is not limited toa special strain but applies to a widevariety of photosynthetic organisms.     

Coproporphyrin production by Rhodobacter sphaeroides under aerobic in the dark and dissolved-oxygen-controlled conditions

Porphyrin production under aerobic in the dark condition was carried out using the photosynthetic bacterium, Rhodobacter sphaeroides IFO12203 and its mutant, CR 386 which can produce 5-aminolevulinic acid (ALA) under aerobic in the dark conditions. IFO12203 produced about 1.0 mg/l of porphyrin even if 2.0 mg of ALA/l was added to the glucose–glutamate–yeast extract (GGY2) medium. However, CR 386 produced 15.0 mg/l of porphyrin after 55 h culture with the addition of 2.0 g of ALA/l and sufficient oxygen supply (dissolved oxygen, DO > 7.0 mg/l). The porphyrin produced by CR 386 consisted only of coproporphyrin III. Under conditions of strict DO control (DO = 2.0 ± 0.2 mg/l), the maximum porphyrin production attained 56.3 mg/l. Low DO (1.0 ± 0.2 mg/l) and high DO control (3.0 ± 0.2 mg/l) did not enhance porphyrin production. It is suggested that oxygen supply seems to control the step(s) of porphyrin biosynthesis of CR 386 in the stages after ALA synthase in the Shemin pathway.     

Participation of Phytohormones in the Stomatal Regulation of Gas Exchange During Water Stress

Almost all processes in the life of a plant are directly or indirectly affected by both stresses and phytohormones. Nevertheless, apart from abscisic acid, the role of phytohormones in plant response to water stress is far from being fully elucidated. This review tries to answer the question whether interactions between abscisic acid and some other phytohormones might be important in the regulation of stomatal opening during water stress and subsequent rehydration. Firstly, it describes the changes in the contents of individual endogenous phytohormones during water stress. Then, it deals with the effects of applied phytohormones on stomatal opening, and on transpiration and photosynthetic rates in different plants species. Finally, it focuses on the alleviation or stimulation of absicic acid-induced stomatal closure by application of other phytohormones. This revised version was published online in July 2006 with corrections to the Cover Date.     

柚树(Citrus grandis)叶片光合作用对补增UV-B辐射的响应

生长在人工光照 4 0 0μmol m- 2 s- 1 下的柚树幼树光合速率的最大值为 1 0 .2± 0 .5μmol m- 2 s- 1 ;而补增UV-B辐射 ( 3.8-4 .2μW cm- 2 ,2 4 5～ 2 97nm,4 5d)的叶片则为 6.4± 0 .8μmol m- 2 s- 1 ,较对照植株降低37.2 %。对照植物的表观量子产率 (固定 mol CO2 mol- 1量子 )为 0 .0 75± 0 .0 1 2 ,而经 UV-B辐射处理植株则为0 .0 4 1± 0 .0 0 8,明显较对照植株低。UV-B辐射处理使植株叶片的光呼吸和不包括光呼吸的 CO2 补偿点增高。对照植株叶片的最大值的 CO2 羧化速率 (μmol m- 2 s- 1 )为 57.1± 1 .5μmol m- 2 s- 1 ,较 UV-B辐射处理的高30 .9% ,而 UV-B辐射处理的植株的光合电子传递速率较对照低 30 %。同时 UV-B辐射植株叶片有较低的光能转化效率 ,其较对照低 39.1 % ,叶片亦含有较低的叶绿素含量。结果表明 ,UV-B辐射明显抑制叶片光合羧化速率和光合电子传递速率 ,UV-B辐射可能抑制包括 Rubisco羧化作用在内的多个光合生理过程 ,降低叶片光合速率。柚树叶片对 UV-B辐射敏感 ,选育抗 UV-B辐射的柚树品种势在必行。     

Effects of Ozone Fumigation on Photosynthesis and Membrane Permeability in Leaves of Spring Barley, Meadow Fescue, and Winter Rape

Seedlings of spring barley, meadow fescue, and winter rape were fumigated with 180 μg kg⁻¹ of ozone for 12 d, and effect of O₃ on photosynthesis and cell membrane permeability of fumigated plants was determined. Electrolyte leakage and chlorophyll fluorescence were measured after 6, 9, and 12 d of fumigation, while net photosynthetic rate (P _N) and stomatal conductance (g _s) were measured 9 d after the start of ozone exposure. O₃ treatment did not change membrane permeability in fescue and barley leaves, while in rape a significant decrease in ion leakage was noted within the whole experiment. O₃ did not change the photochemical efficiency of photosystem 2 (PS2), i.e., F_v/F_m, and the initial fluorescence (F₀). The values of half-rise time (t_1/2) from F₀ to maximal fluorescence (F_m) decreased in fescue and barley after 6 and 9 d of fumigation. P _N decreased significantly in ozonated plants, in the three species. The greatest decrease in P _N was observed in ozonated barley plants (17 % of the control). The ozone-induced decrease in P _N was due to the closure of stomata. Rape was more resistant to ozone than fescue or barley. Apparently, the rape plants show a large adaptation to ozone and prevent loss of membrane integrity leading to ion leakage. This revised version was published online in August 2006 with corrections to the Cover Date.     

Photosynthesis,Transpiration, and Water Use Efficiency of Two Puccinellia Species on the Songnen Grassland,Northeastern China

The intra- and inter-specific variations in net photosynthetic (P _N) and transpiration (E) rates and water use efficiency (WUE) of Puccinellia tenuiflora and Puccinellia chinampoensis leaves were compared. The two species experienced a similar habitat, but differed in leaf area, leaf colour, and nitrogen contents. Leaf P _N and E for both reproductive and vegetative shoots of the two species declined with leaf age. P _N for reproductive shoots was less than for vegetative shoots, but their E was greater than that of vegetative shoots in the dry season. The average P _N and E for reproductive shoots of P. tenuiflora were lower than those of P. chinampoensis, but higher for vegetative shoots.     

灌浆期热胁迫对小麦不同绿色器官光合性能的影响

以4个冬小麦（Triticum aestivem L.）品种（“JD8”、“Jing411”、“Centurk”和“Tam202”）为材料,研究灌浆期热胁迫对旗叶叶片、旗叶鞘、穗下节间、护颖、外疑和芒的光合性能和籽粒产量的影响。结果表明：灌浆期对泪科进行热锻炼也能增加其耐热性且各绿色器官间耐热性差异显。耐热性较强的器官为穗下节间、旗叶鞘和护颖;热敏感器官为旗叶叶片、外颖和芒。热胁迫条件下,穗下节间1旗叶鞘和护颖的细胞膜热稳定性强,光系统Ⅱ原初光能转换效率（Fv/Fm）下降速率以及叶绿素和类胡萝卜素降解速率均低于旗叶叶片、外颖和瓦,穗的净光合速率下降幅度小于旗叶。热胁迫过程中,相对耐热品种“JD8”各器官上述光合参数的下降速度均显低于其他3个热敏感品种。