Leaf carbohydrates assimilation and metabolism affect seed yield of rapeseed with different waterlogging tolerance under the interactive effects of nitrogen and waterlogging

Waterlogging is a main factor causing rapeseed (Brassica napus L.) yield loss, and reasonable nitrogen (N) applications can compensate for this loss. To investigate the effects of N rates on seed yield of waterlogged rapeseed, the waterlogging-tolerant rapeseed variety ZS 9 and sensitive variety GH01 were waterlogged for 0 and 10 days with five leaves at the seedling stage under four N rates (0, 90, 180 and 270 kg/ha). Waterlogging significantly decreased seed yield, while N application can alleviate the yield loss. The yield decrease rate of waterlogged GH01 was greater than that of ZS 9 under the same N rate. During the seedling and bolting stage, the leaf photosynthetic rate (Pn) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity increased, while activities of adenosine diphosphate glucose pyrophosphorylase (AGPase), sucrose synthase (SuSy) and sucrose phosphate synthase (SPS) decreased with more N under the same watering conditions. Compared to the plants without waterlogging, the leaf Pn and Rubisco activity, starch and sucrose contents of waterlogged rapeseed decreased at the two stages; activities of AGPase, SuSy and SPS of waterlogged rapeseed decreased at the seedling while increased at the bolting stage for both the two varieties. At the flowering stage, the Pn, the activities of Rubisco, AGPase, SuSy, SPS and contents of sucrose, starch increased with more N application for both ZS 9 and GH01. Compared to the plants without waterlogging, the Pn and Rubisco activity for waterlogged plants of the two varieties increased; the waterlogged plants of tolerant variety had higher activities of AGPase, SuSy and SPS, while those of sensitive variety was significantly lower. However, the decreased starch and sucrose content were found in both tolerant and sensitive varieties. The activities of AGPase, SuSy and SPS at flowering were highly positively correlated with yield under the interactive effects of N and waterlogging. These results suggested that the flowering stage is the most important stage that N had the positive regulation on waterlogged rapeseed growth. The carbohydrates translocation from leaves to seeds of the tolerant variety were enhanced after waterlogging, while that of the sensitive variety was still inhibited. This was the main reason for the difference in yield between the two waterlogged varieties.     

Photosynthate Unloading from Seed Coats of Phaseolus vulgaris L. an Attempt to Define Conditions Required for Stimulation by Abscisic Acid and Benzylamino Purine

The instablity of the stimulation of photosynthate unloading from seed coats of Phaseolus vulgaris by abscisic acid (ABA ) and benzylamino purine ( BAP ) was studied in terms of experimental conditions. ABA stimulated photosynthate unloading at pH 6 and pH 8 without close dependence upon pH. ABA at a concentration range of 10-5-10-4 mol/L displayed stimulatory effect. However, BAP revealed no effect at a concentration range of 10-6-10-4 mol/L. Experiments designed with different transport time of 14C-photosynthate indicated that ABA might act at the plasma membrane of the unloading cells. Reducing endogenous ABA level by diminishing leaf area did not facilitate the manifestation of exogenous ABA function. Potassium ion stimulated photosynthate unloading from seed coats with highest promotion at 100 mmol/L K . However, no dependence of ABA stimulation of photosynthate unloading on K was found.     

优质早籼稻品种的库、源、流特性研究

以优质早籼稻品种佳禾早占为对照,研究优质早籼稻新品种泉珍10号、佳辐占与漳佳占的库、源、流特性。结果表明,泉珍10号库容量大,填库能力强,冠层叶挺直,叶面积指数大,干物质积累总量大,开花后茎鞘干物质向穗部运转量大,对稻谷的贡献率大;佳辐占和漳佳占的库、源、流特性有许多相似之处;佳辐占与漳佳占的主要差异:佳辐占穗粒数少,千粒重较大;漳佳占正好相反。     

14C同化物在黄柏韧皮部的运输速率测定

以14C为示踪剂,用14CO2 CO2混合气体法进行半株标记,饲喂50μCi/株的NaH14CO3,标记时间为lh.燃烧法制样,在FJ2107P液体闪烁计数器上测定,14C同化物在黄柏韧皮部中的运输速率为47～54 cm/h,平均速率为50.2 cm/h.     

缺镁对龙眼光合产物生产和分配的影响

缺镁对龙眼 (DimocarpusLonganaLour.)光合产物的生产和分配有明显的影响。缺镁胁迫下 ,龙眼叶片单位面积和单位重量的叶绿素、类胡萝卜素含量均降低 ,光合速率下降 ,叶绿体亚显微结构发生明显的改变 ,叶绿体中可见有大量的淀粉粒。随着缺镁胁迫程度的加重 ,14 C -光合产物在标记叶中的滞留量增加 ,输出率降低。叶片非还原糖、淀粉含量增加 ,茎秆、根系的非还原糖尤其是淀粉含量降低。本文还就缺镁影响龙眼光合产物生产和分配的机理进行了讨论     

利用~（14）C示踪法研究杉木光合产物分配和杉木根系分泌物

用￣（１４）Ｃ示踪法研究了杉木光合产物的分配和杉木根系的分泌物。结果表明，杉木饲喂￣（１４）ＣＯ２后１天，光合产物大部分滞留在叶中，只有２７．３８％从叶中输送到新梢、主枝、根和侧枝中，标记后３天，光合产物分配率仍以叶为最高，但所占百分比下降，而主枝、新梢、根和侧枝的分配率相应地有了增加，至标记后２２天，光合产物的分配率以新梢为最高，其次为根，叶退居其后。杉木光合产物输送到根部后，可很快转化为分泌物并排出体外，其分泌量在标记后第４天出现峰值，此后￣（１４）Ｃ分泌物量不断下降。杉木根系分泌物中的有机小分子物质，以糖类为最多，其次是有机酸，氨基酸居第三。     

ABA对水稻花后剑叶光合产物输配作用的示踪动力学研究

运用示踪动力学分析方法,分析 ABA 涂稻穗及剑叶后,剑叶中几种光合产物的变化,发现 ABA 涂稻穗后,能抑制剑叶中暂不输配物质的形成,对可输配物质的形成与光合产物的输出速率具促进作用。ABA 涂剑叶后,对暂不输配物质、结构物质与呼吸消耗具抑制作用,对可输配物质的形成具促进作用。     

PHOTOSYNTHETIC ACCLIMATION AND DECREASED CHLOROPHYLL(A + B) CONCENTRATIONS OCCUR IN NITROGEN-SUFFICIENT TOBACCO LEAVES IN RESPONSE TO CARBON DIOXIDE ENRICHMENT

Effects of carbon dioxide (CO₂) enrichment on plant growth and on nitrogen partitioning were examined in tobacco (Nicotiana tabacum L. cv. ‘Samsun’). Dry matter, leaf area and specific leaf weight were unchanged (P > 0.05) by CO₂ enrichment. Total soluble protein, soluble amino acids and inorganic nitrate also were unaffected by CO₂ enrichment (P > 0.05). Leaf chlorophyll (a + b) levels decreased 13% (P ≤ 0.05) in response to CO₂ enrichment. The diurnal accumulation of soluble amino acids was delayed and the initial slope of the A/C _i response curve was decreased 14% in the elevated compared to the ambient CO₂ treatment. The above findings showed that CO₂ enrichment affected leaf chlorophyll levels, diurnal soluble amino acid metabolism and photosynthetic responses to low intercellular CO₂ concentrations even though the plants were nitrogen sufficient. Inadequate nitrogen fertility cannot explain all of the effects of CO₂ enrichment on photosynthesis by tobacco leaves.     

高产冬小麦旗叶光合产物供应能力的研究

对冬小麦旗叶光合产物供应能力在供应速率（包括光合作用和蔗糖合成的速率）和供应持续期两个方面进行了研究,结果表明：与鲁麦14相比,鲁麦22旗叶光合速率,灌浆中后期旗叶磷酸蔗糖合成酶（SPS）活性高,表明鲁麦22旗叶光合产物供应速率高;鲁麦22旗叶叶绿素含量高于鲁麦14,超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性高,而丙二醛（MDA）含量低于鲁麦14,即光合产物供应持续期长。因而鲁麦22形成更高的生物产量和籽粒产量。