不同施肥水平对南瓜RuBP羧化酶活性的影响

采用L^9（3^4）正交试验设计,系统的研究了不同施肥条件下南瓜穴盘苗的RuBP羧化酶活性。结果表明,氮素对南瓜穴盘苗的RuBP羧化酶活性影响最为显著。施用氮肥后,RuBP羧化酶活性显著降低;磷钾对南瓜穴盘苗的RuBP羧化酶活性影响最小,磷钾施用后,RuBP羧化酶活性与对照差异不显著。微肥对南瓜穴盘苗RuBP羧化酶活性的影响介于前两者之间,也使RuBP羧化酶活性较明显地降低。     

Evaluation of the Heterosis on Leaf Photosynthesis of Remote-Cross F1 Rice (Oryza saliva L.)

The heterosis of leaf photosynthesis was studied on the main characters included in the range from CO₂exchange rate (CER) to enzymatic activity using a remote cross F, rice. The CER was significantly higher than those of the parental strains, showing a 111 % heterosis effect on average; at the same time strong heterosis was observed for the leaf area production and growth. Also stomatal and mesophyll conductances increased in the F₁ rice, which may contribute to the increase in CER. Chlorophyll content (Ch1), soluble protein content (SPC) and ribulose 1,5-bisphosphate (RuBP) carboxylase activity (RCA) were measured as the internal factors related to photosynthesis, and compared between the F₁, rice and the parents. For all these factors, the F₁ rice showed low values compared to the parents. Positive heterosis was not expressed here. On the other hand, the specific activity of RCA (RCA/SPC) increased in the F₁, rice, showing a 120% heterosis effect. This may be regarded as one of the main causes for the increase in CER of the F₁, rice. High CER expressed as heterosis concurrently with large leaf area production is one of the important findings in our study, and this may suggest a high possibility of further improvement in biomass production or yield of rice by gathering the advantageous elements into a hybrid plant.     

Root restriction-induced limitation to photosynthesis in tomato (Lycopersicon esculentum Mill.) leaves

Root restriction often depresses photosynthetic capacity and the mechanism for this reduction, however, remains unclear. To identify the mechanism by which root restriction affects the photosynthetic characteristics, tomato (Lycopersicon esculentum Mill.) seedlings were subjected to root restriction stress with or without supplemental aeration to the nutrient solution. With the development of the root restriction stress, CO₂ assimilation rate was decreased only in confined plants without supplemental aeration. There were also significant decreases in leaf water potential, stomatal conductance (g_s), intercellular CO₂ concentration (C_i), and increases in the stomatal limitation (l) and the xylem sap ABA concentration. Meanwhile, the maximum carboxylation rate of Rubisco (V_cmax) and the capacity for ribulose-1,5-bisphosphate regeneration (J_max) also decreased, followed by substantial reductions in the quantum yield of PSII electron transport (Φ_PSII). Additionally, root restriction resulted in accumulation of carbohydrates in various plant tissues irrespective of aeration conditions. It is likely that root restriction-induced depression of photosynthesis was mimicked by water stress.     

基于FvCB模型估算小麦的最大电子传递速率

在Farquhar、von Caemermer和Berry模型(以下简称FvCB生化模型)中有2个子模型,即非直角双曲线模型和核酮糖-1,5-双磷酸(RuBP)再生速率限制模型,用其可以估算C_3植物叶片的最大电子传递速率(J_(max))。为了严格验证由这2个子模型估算植物叶片J_(max)的精确度,本研究用LI-6400-40光合测定仪分别测定了2%和21%O_2浓度下小麦(Triticum aestivum L.)叶片的光合速率和电子传递速率对光和CO_2的响应曲线,并用此2个模型分别拟合了21%O_2浓度下小麦光合速率对CO_2的响应曲线和电子传递速率对光的响应曲线。结果表明,由非直角双曲线模型拟合小麦电子传递速率对光的响应曲线得到的J_(max)为254.86μmol·m~(-2)·s~(-1),显著高于其观测值(236.37μmol·m~(-2)·s~(-1))(P0.05);由RuBP再生速率限制子模型拟合小麦光合速率对CO_2的响应曲线得到的J_(max)为260.58μmol·m~(-2)·s~(-1),则显著低于其观测值(298.05μmol·m~(-2)·s~(-1))(P0.05)。此外,当胞间CO_2浓度(C_i)为738.01μmol·mol~(-1)时,小麦处于RuBP再生速率限制阶段,此时其净光合速率及其相应的光呼吸速率分别为61.16和8.55μmol·m~(-2)·s~(-1)。在不考虑其他路径消耗光合电子的情况下,小麦在该C_i时同化这些碳至少需要光合电子流为352.24μmol·m~(-2)·s~(-1),这与由RuBP再生速率限制子模型估算的J_(max)(260.58μmol·m~(-2)·s~(-1))之间存在显著差异(P0.05)。这说明非直角双曲线模型和RuBP再生速率限制子模型在估算小麦叶片J_(max)上存在缺陷,有待改进。     

不同水稻品种对低氮反应的差异及其机制的研究

在低氮(中度缺乏)和高N(丰足)条件下,地上部干物质生长量和稻谷产量在供试品种间的差异顺序为:汕优64>汕优6号>浙丽1号>秀水48,其中杂交稻与常规稻的差异最大,低N条件下的差异又比高N条件下的明显。结果还表明在低N条件下产量较高的品种吸收利用土壤中N素能力较强,其相关的生物学和生理学特征为:1.根系发达,根系生长量、分布密度以及根对NH₄⁺的亲和力均较大;2.地上部干物质生产量和功能叶氮、碳同化代谢关键酶,即硝酸还原酶,各氨酸合酶,RuBP羧化酶的活力均较高。此外RuBP羧化酶活力以及其水平受氮素的提高效应也N-高效品种较明显。这些特性均可以作为筛选和鉴别N-高效作物基因型的生理生化指标。     

氮肥水平对杂交稻汕优63剑叶光合速率和RuBP羧化酶活性的影响

用低氮(LN)、中氮(MN)、高氮(HN)盆栽土培的杂交水稻汕优63为材料,测定其剑叶的光合速率、RuBP羧化酶含量及活性、可溶性蛋白和叶绿素含量的变化.结果表明:随着氮水平的提高,叶面积增大,气孔密度减少,RuBP羧化酶活性和光合速率增加.随着叶龄的增加,三个不同氮水平的叶片中RuBP羧化酶蛋白下降均先于可溶性蛋白的下降;HN组的光     

氮钾营养对长豇豆豆荚产量品质及几种酶活性的影响

在广州秋季以长豇豆锦穗白豆角品种为材料，设置低氮低钾（Ｎ１０Ｋ１０）、低氮高钾（Ｎ１０Ｋ２０）、高氮低钾（Ｎ２０Ｋ１０）和高氮高钾（Ｎ２０Ｋ２０）４个处理，研究氮钾营养水平对长豇豆豆荚产量，品质以及叶片乙醇酸氧化酶，核酮糖－１，５－二磷酸加氧酶和硝酸还原酶等活性的影响。结果表明低氮低钾处理的豆荚产量与其他处理无明显差别，但品质稍差。增钾可提高豆荚产量和品质，增氮无增产意义。长豇豆生育期间ＮＲ、ＧＯ和ＲｕｂｉｓＯ活性均呈单峰曲线变化，ＮＲ活性在开花结荚初期最高，ＧＯ和ＲｕｂｉｓＯ活性则抽蔓期最高。４个处理对叶片ＮＲ、ＧＯ和ＲｕｂｉｓＯ活性的影响一致，低氮低钾处理最低，增氮或增钾都提高它们的活性，以增氮为明显。     

Seasonal Patterns of Photosynthetic Traits in Early Maturing Maize

A biochemical approach to maize breeding must be based on an exact knowledge about changes of relevant traits with ontogenetic stage. In 1983 seasonal patterns of net assimilation rate (NAR), chlorophyll and carotenoids contents, and of activities of RuBP carboxylase, PEP carboxylase and NADP malate dehydrogenase were recorded for two early maturing maize cultivars. For all traits the general trends were similar for both cultivars throughout the growing season but short term fluctuations were less synchronized after anthesis. About 75% of the maximum green leaf area was expanded within 20 days around middle of July. Specific seasonal patterns were observed for all traits. Before anthesis values were maximum for NAR in late June and in early July, for enzyme activities at the end of June and for pigment contents at the beginning of July. First decreases occurred for all traits before anthesis, further decreases were observed for PEP carboxylase in August and for chlorophyll content in September. Marked temporary declines coincided for NAR and pigment contents with a cold spell end of June and for these traits and RuBP carboxylase activity with anthesis. Evidence was scarce that any of the photosynthetic traits reflected the photosynthetic efficience of the two cultivars for a long stretch of time.     

抗草甘膦基因(EPSPS)植物双价表达载体的构建

针对目前报道的抗草甘膦转基因作物中,强组成型启动子驱动抗草甘膦基因在转基因植物的所有部位和所有发育阶段都表达,增加植株代谢负担,对植物的产量可能引起负效应的这一问题,利用Ag2这种草甘膦胁迫诱导启动子来驱动epsps基因,只在草甘膦喷施后高效表达对草甘膦的抗性.另外,同时利用具有组织特异性的启动子RuBP,使epsps基因在植物草甘膦农药田间喷施主要部位叶片中高效表达,应可以进一步增强转基因植物的抗草甘膦能力,但又不致过多地增加转基因植物的代谢负担,以利培育高抗草甘膦且农艺性状优良的转基因植物.实验分别以pBI121-E-M-Bt(Kanar)和pBI121-CP4E(Kanar)质粒为基础,通过载体pUC19及对EcoRⅠ位点的接头改造,构建了由RuBP启动子和新发现的诱导型启动子Ag2共同调控epsps基因的植物表达载体pGBI-Ag2EM-RuBPEM和pGBI-Ag2CP4E-RuBPCP4E,选择标记为卡那霉素,通过冻融法将重组质粒导入根癌农杆菌LBA4404,并通过农杆菌介导的浸花法转化拟南芥,获得了T0代种子,为利用epsps基因改良植物对草甘膦的抗性奠定了物质基础.