Weight of individual grains is a major yield component in wheat. The non-uniform distribution of single grain weight on a wheat spike is assumed to beelosely associatted with starch synthesis in grains. The preseint study was undertaken to determine if the enzymes involved in starch synthesis caused the difference in single grain weight between superior and inferior grains on a wheat spike. Using two high-yield winter wheat (Tritieum aestivum L.) varieties diffeing in grain weight and theree nitrogen rates for one varity, the contents of amylse and amylopection, and activities of enzymes involved in starch synthesis in both superior and inferior grains were investigated during the entire periol of grain filling. Superior grains showed generally higher starch accumulation tates and actieties of enzymes ineluding SS (sucrose synthaes), UDPGP Pase (UDP-glucose pyrophosphorylase), ADPGPPase (ADP-gluceose pyrophosphorylase), SSS (soluble starch synthase) and GBSS (starch granule bound starch synthase) and subsequently produced much higher single grain weigth than inferior grains. Nitrogen inereased enzyme activities and starch accumulation rates.and thus improved individual grain weight, especially for inferior grains. The SS. ADPGPPase and SSS were significantly correlated to amylopectin accumulation, while SS, ADPGPPase, SSS and GBSS were signinficantly correlated to amylose accumulation. This infers that SS, ADPGPPase and starchsynthase play key roles in regulating starch accumulaition and grain weight in superior and inferior grains on a wheat spike.

Quantifying dry mattcr partitioning into individual organs of plants is a key component for simulating crop growth and yicld formation. This study was undertakcn to develop a dynamic module of biomass partitioning over the entire duration of growth in wheat. The paritioning fraction of shoor or rool was defined as the fraction of its dry weight in plant biomass, and partitioning fraction of green leaf, stem or ear as the fraction of its dry weight in shoot mass of wheat. The functional relationships of the partitioning fraction with physiological development time for the entire growth period were established, in which harvest indes (HI) regulated partitioning fraction of ear to shoot biomass as a genetic parameter. The dry weight of individual organ was the product of the respective partitioning fracton and plant weight or shoot weight. Test of the model with the field experiment data sets involving differen sowing dates, plant weight of shoot weight. Test of the model with the field experiment data sets involving different sowing dates, plant densities and nitrogen fertilization strategies indicated a good agrecment between the predicted and observed values.

研究了小麦（Triticum aestimum L.）茎顶端不同类型原基分化的动态过程，以明确原基分化的综合模式，并建立了不同原基分化之间的定量关系。结果表明，小麦叶原基和苞叶原基分化与播后累积生长度日（GDD, growing degree days after sowing）的关系呈S形曲线，而小穗原基和小花原基为上升段抛物曲线，从分化模式看，苞叶原基具备营养器官原基特征；小穗和小花原基的分化进程能较好地反映基因型和生态条件对顶端发育的影响。小麦茎顶端原基分化的综合模式为由三段子模式构成的近似S曲线，叶原基数由基因型和环境条件共同决定，而苞叶原基、小穗原基和小花原基数以环境因子的影响为主。以平均热间距来衡量，适期播处理的叶片、苞叶和小穗原基分化速率最高；而小花原基数与小花分化持续期之间的数量关系最为密切。研究结果有助于提示和理解小麦茎顶端发育的生物学规律。

蔗糖向淀粉的转化是决定小麦籽粒产量的重要因素。田间条件下研究了两个小麦（Triticum aesivum L.)品种“鲁麦22”和“鲁麦22”和“鲁麦14”籽粒淀粉合成相关酶：蔗糖合酶（sucrose synthase, SS）、腺苷二磷酸葡萄糖焦磷酸化酶（ADP-glucose pyrophosphorylase, ADPGPPase）、可溶性淀粉合酶（soluble starch synthase, SSS）、束缚态淀粉合酶（starch granule-bound synthase, GBSS）的活性以及籽粒ATP含量的日变化。结果表明，上述酶活性呈现明显的昼夜变化特征，酶活性一般在白天较低，而在夜间呈较高活性，而籽粒ATP含量趋势相反。相关分析表明，白天较低的酶活性可能与气温超过其适宜温度有关。对籽粒淀粉合成相酶活性日变化的可能因子进行了讨论。

This study was undertaken to determine the time-course of floret primordium initation and degeneration in relation to thermal time after sowing in various cultivars and tiller position sof wheat (Triticum aestiveum L.). The field experiment was carried out on the experiment station of Nanjing Agricultural University of China. and included three sowing dates: carly planting of 30 September. middle planting of 30 October and late planting of 2 march and two wheat cultivars: winter type 'Jing 411' and spring type 'Yangmai 158'. Quadratic and linear relationships could deseribe floret initiation. degeneration and abortion in response to growing-degree-days after sowing for main stem and first and second tillers of middle planting plants of both cultivars. The floret fertility. The growing-degree-days from sowing to floret intiaion were significantly diffeent between the thre sowing dates and between the two cultivars. These results help quanitfy the dynamic processes of apical development and explain differcnes in floret development of wheat with different environments. cultivars and tiller development and explain the diffences in floret development of wheat with different environments. cultivars and tiller positions.