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。

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.

Accumulation of protein and starch in grain is a key procss determining grain yield and quality in wheat. Under drought or waterlogging, endogenous plant hormone levels will change and may have and impact on the yield and quality of wheat. In a greenhouse experimnet, four winter wheat (Triticum aestivum L.) varieties differing in grain protein conternt. Heimai 76. Wanmai 38. Yangmai 10 and Yangmai 9, were subjected to drought (SRWC=45～50%, DR). waterlogging (WL) and moderate water supply (SRWC=75～80%, CK), beginning form 4 days post-anthesis (DPA) to maturity. On the 10 (grain enlargemet stage) and 20 (grain filling stage) DPA. endogenous in sink and source organs of wheat plants by enxymc linked immunosorbent assay (ELISA). The patterns of hormonal changes were similar in four varieties. The ABA levels were much higher under DR and WL than under CK. Compared with CK, GA1+3 levels in whole-plant under DR and WL changed a little at 10 DPA, but markedly dectrease under DR and WL at 20 DPA. Changes of enodgenous IAA level under DR and WL exhibited a complicated pattern, depending on organs and growth stages. Particularly at the 20 DPA, the mean levels of IAA in roots. leaves and grains decreased significantly under DR and WL. In comparison with CK. ZR levels in all organs significantly decreased under DR and WL at both stages. The correlation analyses between yiclds and contents of starch and protein in grains and levels and rations of four hormones in source and sink organs indiated that the changes in yield and content of grain starch and protein under DR and WL were associated with the reduced IAa, ZR and GA, levels and elevated ABA level in plants, expecially in grains. It was proposed that the changed levels of endongenous hormones under post-anthesis DR and WL might indirectly affect protein and starch accumulation in grains by influencing the regulatory enzyines and rpocesses.

The effect of environmental changes on the rate of leaf emergence in wheat Triticum aesiveum L. must be understood to accurately simulate the development of the crop canopy. We determined the phyllochron for 'stephens' winter wheat plants in growth chambers at two constant temperatures (10 and 18℃) at a daylength of 14h and at two constant daylengths (8 and 18h) at a temperature of 20℃, and for plants transferred between the two temperatures and between the two daylengths at the first-, second--, third-, and fourth. leaf stages. The phyllochron of all plants transferred from low to high temperature increased to that of plants kept continually at the high timperature. The phyllochron of plants transterred from high to low temperature at the one-leaf stage was identical with the phyllochron of plants kept continually at the low temperature, but was intermedite between that of the high and low temperatures for gransfers at the second-, third, or fourth-leaf stage. The phyllochron of plants transferred from short to lone days decreased to values identical to those plants transferred from long to short daylengths increased to values equal to or greater than that of plants kept continually at the short daylengths. Thus. plants adapted to either tmperature or day length environments that favor rapid leaf environment for leaf growth than plants that were kept continually in the less favorable environment. The results help explain why the phyllochron is often constant for a particular field planting where plants are subject to seasonal changes in tmperature and daylength.

Simulationg of phasic development in wheat is necessary in constructing wheat growth and yield models. It is also useful for evaluating culvivar adaptation and scheduling cultural practices. This paper describes a conceptual model of wheat development based on phenological principles, as affected by vernalization, photoperiod, thermal response and intrinsic earliness, and also reports the results of ensitivity analysis and validation of the model. The model predicts when the plant will reach double ridge, termianl spikelet and heading. In tthe model, the daily thermal sensitivity of development following emergece is determined by and interacton of relative vernalization comptetion and relative photoperiod effectiveness for that day. After complete vernalixation is reached, the daily thermal sensitivity is determied only by relative photoperiod effectiveness, which gradually increases from terminal spikelet to heading. A multiplication between the daily thermal sensitivisty and thermal effectiveness generated daily flowering were characterized as vernalization requirement, photoperiod sensitivity and intrinsic earliness. The model showed a sensitive response to environmental varibles of temperature and daylength. and to gentic parameters of vernalizaion requrement and photoperiod sensitivity. Evaluation of the model using multiple experimental data involving varous cultivars and planting dates exhibited a marked goodness of fit between simulation and observation with a root mean square error<5 days. The results indicate that the model can be used a prdictor for the major flowering stages. as well as functioning as dnowledge for understading the characteristics of different develoment componcets in wheat.