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.

Nondestructive moitoring and diagnosis of plant N status is necessary for precision N management. The present study was conducted to determine if canopy reflectance could be used to evaluate leaf N status in rice (oryza sativa L.). Ground-based canopy spectral reflectance and N concentration and accumulation in leaves were measured over the entire rice growing season udner various treatments of N feritlization, irrigation, and plant population. Analyses were made on the relationships of seasonal canopy spectral reflectance, ratio indices, and normalized difference indices to leaf N concentration and N accunulation in rice under different N treatments. The results showed that at each sampling date, leaf N concentration was negatively related to the reflectance at the green band (560nm) while positively related to ration index, with the best correlation at jionting. However, the relationships between leaf N accumulation and reflectance at green band and ration index were consitent across the whole growth periold. The ratio of near infraed (NIR) to green (R480/R560) was especiallly linearly related to total leaf N accrmulation, independent of N level and growth stage. Tests of the linear regression model with different field experiment data set involving diffeent plant densities, N fertilization, and irrigation treatments exhibited good agreement beweent the prediceted and boserved values, with an estimation accuracy of 96.69%, root mean square error of 0.7072, and relative error of -0.0052. These results indicate that ratio inex of NIR to Green (R06/R560) should be useful for nondestructive monitoring of N Status in rice plants.

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。

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.

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.