Effects of irrigation strategies and soils on field-grown potatoes: Gas exchange and xylem [ABA]

Gas exchange was measured in potatoes (cv. Folva) grown in lysimeters (4.32 m²) in coarse sand, loamy sand, and sandy loam and subjected to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation strategies. PRD and DI as water-saving irrigation treatments received 65% of FI and started after tuber bulking and lasted for six weeks until final harvest. Midday photosynthesis rate (A_n) and stomatal conductance (g_s) of fully irrigated (FI) plants were lowest in coarse sand and mean A_n of diurnal measurements in FI, PRD and DI tended to be lower in this soil as compared with the loamy sand and sandy loam. The results revealed that diurnal values of A_n and g_s in PRD and DI were consistently lower than FI without reaching significant differences in accordance with findings that xylem [ABA] in PRD was significantly higher than FI, and tended to be higher than in DI. Diurnal measurements showed that A_n reached peak values during mid-morning and midday, while g_s were highest during the morning. Intrinsic water use efficiency (A_n/g_s) correlated linearly well with the leaf to air vapor pressure deficit (VPD) and the slope of the line revealed the rate of A_n/g_s increase per each kPa increase in VPD, i.e. approximately 10 μmol mol⁻¹. Transpiration efficiency (A_n/T) of PRD was higher than DI, which shows slightly better efficient water use than DI. The slope of the linear relationship between transpiration efficiency and VPD decreased from −2.03 to −1.04 during the time course of the growing season, indicating the negative effect of leaf ageing on photosynthesis and thus on plant water use efficiency. This fact shows the possibility to save water during last growth stages through applying water-saving irrigations without much effect on transpiration efficiency.     

秸秆预处理中木质纤维物质含量测定方法的研究进展

对国内外主要应用的木质纤维物质的测定方法进行了综述,归纳了各方法的特点与应用情况,并对生物质能源领域内木质纤维物质分析方法的发展方向进行了展望。     

收获期猕猴桃树体钙素营养分布研究

[目的]研究收获期猕猴桃树各器官的生物量、钙含量和钙累积量。[方法]钙含量用HNO3-HClO4消解后用等离子光谱仪测定,钙累积量为钙含量与各器官干重的乘积。[结果]收获期猕猴桃各器官钙含量差异明显,表现为：叶〉根〉茎〉果实,细根高于粗根,老茎大于幼茎;皮层钙含量远高于木质部。在木质部中,根钙含量大于茎;在皮层,根大于1年生枝和2年生枝,小于主干和多年生枝。猕猴桃整株钙累积量为127．36g,根〉茎〉叶〉果实,分别为49,29、43．12、23．30和11．65g,分别占整株钙累积量的38．64％、33．80％、18．26％和9．13％。猕猴桃树整株木质部和皮层生物量分别为4．79kg和2．65kg,分别占树体总生物量的33．45％和18．51％。皮层钙累积量为57．49g,占树体总钙累积量的45．14％,而木质部钙累积量只有11．83g,仅占树体总钙累积量的9．29％,不到皮层的1／4。[结论]该研究初步探索了钙素在猕猴桃树体的分布情况,具有一定的理论和买践意义。     

木本植物木质部栓塞的形成和修复的几点补充

对木质部栓塞的变化规律、不同的因素对栓塞的影响、栓塞的修复现象以及栓塞的修复机理进行了论述,在对以前的相关综述的基础上进行相应的补充。     

Causes of defoliation and low survival rate of grafted sweet pepper plants

We investigated the cause of defoliation in sweet pepper (Capsicum annuum L.) plants after grafting. Grafted plants of old-stage sweet pepper showed a higher defoliation rate than young-stage grafted plants. Old-stage grafted plants had lower stomatal resistance and water potential than young-stage plants, and showed poorly developed xylem connections at the graft site. Foliar application of abscisic acid (ABA) to the grafted plants increased stomatal resistance and water potential, decreased the defoliation rate, and promoted graft take among old-stage plants. Our results indicated that low stomatal resistance under low humidity induces water stress, defoliation, and low survival rate in old-stage grafted sweet pepper plants. ABA treatment increased stomatal resistance, water potential, and survival rate, and decreased the defoliation rate among old-stage sweet pepper plants.     

植物木质部导管梯状穿孔板流动阻力特性研究

简述了目前国内外植物木质部穿孔板流体建模研究概况,对穿孔板孔口流动特性进行了数学建模,利用Fluent软件对不同几何结构的穿孔板孔口附近的水分流动进行流场仿真,通过计算和分析仿真结果,研究了穿孔板倾斜角、导管内径、穿孔板孔数、等效孔宽对穿孔板流阻系数的影响规律.结果表明,当其他参数设定时,倾斜角增大,平均流量不变,穿孔板两侧的总压降及流阻系数先减小后增大;导管内径增大,平均流量增大,总压降减小,流阻系数减小;孔数增加,平均流量不变,穿孔板总压降增加,流阻系数也增加;等效孔宽增大,平均流量保持不变,总压降与流阻系数均减小.     

Transport via xylem of atrazine, 2,4-dinitrotoluene, and 1,2,3-trichlorobenzene in tomato and wheat seedlings

Transport of atrazine (ATR), 2,4-dinitrotoluene (DNT), and 1,2,3-trichlorobenzene (TCB) from roots to shoots via xylem of wheat and tomato seedlings was measured following a 24-h exposure of plant roots to hydroponic solutions of these organic compounds. Transport of the compounds from roots to shoots reached equilibrium within 24 h, consistent with an earlier finding. Low concentrations of TCB were detected in the final external solution and the xylem efflux of control wheat seedlings. This suggested that there was a fast foliar uptake of TCB and its downward movement via phloem of the wheat seedlings. Concentrations of DNT, ATR, and TCB in xylem effluxes of wheat and tomato increased significantly with increases of their external concentrations. The translocation stream concentration factors (TSCF), i.e., the ratios of the concentrations in xylem sap to those in external solution, of the compounds with tomato seedlings followed the order of ATR > DNT >> TCB, which was inversely correlated with the log K_ow (the octanol–water partition coefficient) of the compounds. The observed xylem transports of DNT and TCB from roots to shoots with wheat seedlings were lower than those with tomato seedlings. ATR exhibited a high xylem transport with the two plant species, which resulted presumably from an atrazine–metal complex formation.     

Embolism Occurrence in Relation to Water Supply in Xylem of Winter Wheat Leaves

Embolism occurrence in the xylem of leaves was investigated in field-grown winter wheat(cv.9195) under droughted and irrigated conditions by ultrasonic acoustic emission (AE)monitoring with drought stress monitor (Model 4615, Physical Acoustics Corp., USA) inthe growing seasons of 1998-2000. The measurements have revealed a pattern of 3 activeAE periods for daily AE signals. The 1st active period generally occurred between 10:00-11:00, the 2nd was often observed around 18:00, and the 3rd was at about midnight, AEsusually ceased after 0:00-2:00. AE rates during these periods varied with soil moisture,weather conditions and growth stages, etc. as shown in Fig. 1. The 3rd one was occasionallymissing on severe drought soils. Irrigation often led immediately to higher AE rates overthe ensued 2nd period. Droughted plants having greater amount of 24 h AEs showed higherdegrees of embolism than the irrigated ones during early jointing stage. However, thetotal of 24 h AEs of droughted wheat decreased by 66 and 82% compared with that irrigatedat middle and late stages respectively. This phenomenon was here termed "AE attenuation",which was regarded as an implication of incomplete embolism refilling overnight due tosevere soil moisture depletion. Considerable amount of AE signals were also recordedfrom plants on wet soils. It is suggested by the authors that cavitations and embolismmight be a physiological response to the daily rapid establishment of water potentialgradient within xylem system in the morning, rather than merely a phenomenon resultingfrom water stress.     

样品制备方法对高效液相色谱法测定红松树干中可溶性糖的影响

以红松（Pinus koraiensis）木质部和韧皮部为研究材料，从提取方法、粉碎程度、提取次数、色谱条件以及重现性、精密度、回收率等方面对木质化器官糖类——果糖、葡萄糖和蔗糖的样品制备方法进行了研究。超声法较水浴法能使韧皮部3种可溶性糖提取率提高2％-15％（P〉0．01），但是可以使木质部可溶性糖的提取率提高57％～73％（P〈0．01）。韧皮部和木质部样品可溶性糖的提取率随着提取次数的提高均呈现显著升高的趋势，LangrnuirEXT1能够很好地模拟这种关系，在保证3种糖类均达到90％的精度下，木质部和韧皮部的提取次数需要至少3次。样品粉碎程度对木质部和韧皮部糖类提取效果表现不同：木质部样品的粉碎粒径为0．15mm时，3种糖类的提取效果最高；韧皮部样品粉碎得越细，可溶性糖的提取效果越好，指数模型模拟效果很好（r^2〉0．9）。     

木薯块根迅速膨大期韧皮部和木质部中的蔗糖代谢

以高淀粉木薯品种华南9号和低淀粉品种华南7号为试料,分析块根膨大中后期蔗糖代谢相关酶活性及其产物的变化规律。结果表明:在块根韧皮部和木质部中,参与蔗糖合成的蔗糖磷酸合成酶和蔗糖合成酶(合成方向)在膨大后期活性均有所升高,而参与蔗糖分解的可溶性酸性转化酶、中性转化酶和蔗糖合成酶(分解方向)在后期活性均下降;细胞壁酸性转化酶活性变化存在明显差异,华南7号在块根膨大中期活性较高,华南9号在后期较高;在块根韧皮部中,蔗糖、葡萄糖和果糖的含量在膨大后期增加幅度较华南7号明显,而在块根木质部中,华南7号中这3种糖在膨大后期均呈增加趋势,华南9号中却下降,表明华南9号比华南7号有更强的蔗糖代谢的能力,这可能是造成不同品种木薯淀粉含量差异的原因。