高光谱成像技术的不同叶位尖椒叶片氮素分布可视化研究

为了快速、准确、直观估测尖椒叶片的营养水平和生长状况,利用高光谱成像技术结合化学计量学方法对不同叶位尖椒叶片氮素含量(nitrogen content,NC)的分布进行了可视化研究。按照叶片位置采摘尖椒叶片,并采集高光谱数据,然后测定相应叶片的SPAD和NC。提取出叶片的光谱信息后,采用Randomfrog(RF)算法提取特征波段,分别选出5条与10条特征波段。针对选取的特征波段和全波段,分别建立偏最小二乘回归(partial least squares regression,PLSR)模型,结果表明采用特征波段建立的PLSR模型性能较好(SPAD:R_C=0.970,R_(CV)=0.965,R_P=0.934;NC:R_C=0.857,R_(CV)=0.806,R_P=0.839)。根据预测模型计算尖椒叶片高光谱图像每个像素点的SPAD与NC,从而实现SPAD与NC的可视化分布。事实上叶片的SPAD在一定程度上可以反映含氮量,二者分布图的变化趋势基本一致,验证了可视化结果的正确性。结果表明:运用高光谱成像技术可以实现对不同叶位尖椒叶片氮素分布的可视化研究,这为监测植物的生长状况和养分分布提供理论依据。

不同施氮水平对晋单84不同叶位叶片含氮量及产量的影响

由于不同叶位叶片含氮量存在较大差异,确定各生育期最能代表植株氮营养状况的叶位,是利用叶片反射光谱进行玉米氮营养状况精确诊断的前提。采用不同施氮处理对晋单84在拔节期、大喇叭口期、抽雄期不同叶位叶片含氮量、植株含氮量、籽粒产量及其相关性进行研究。结果表明,拔节期以第6叶位(最上部完全展开叶)以及大喇叭口期、抽雄期以第12叶位(穗位叶)叶片含氮量与植株含氮量的相关性最好,这3个叶位分别作为3个生育期的植株含氮营养指示叶位。随着施氮水平的提高,各生育期相同叶位叶片含氮量也相应增加,而且氮营养指示叶位叶片的含氮量受增施氮肥的影响较低叶位更大,增施氮肥能够增大指示叶位与其他叶位叶片的含氮量差异,即叶位差距越大,含氮量差异越大。

渍害下小麦相对叶绿素含量的降低效应及其与产量的相关性

为了探讨渍水对小麦(Triticum aeestivum)叶片的相对叶绿素含量的降低效应及其与产量的相关性,以来源于不同麦区推广品种和高代品系共164份为材料,在抽穗扬花期进行人工模拟渍害处理,以正常水分区为对照,分别测定渍水前和渍水后不同品种(系)倒1叶~倒4叶的SPAD值(相对叶绿素含量),成熟期测定其产量,计算不同品种(系)的SPAD值和产量的渍害指数,然后进行比较分析。结果表明,小麦抽穗扬花期渍水SPAD值显著下降,不同叶位叶片的SPAD值下降程度差异显著。渍水12d对倒1叶SPAD值的影响不显著,对倒2叶~倒4叶的SPAD值的影响均达到极显著水平;对照区渍水处理前后的倒2叶的SPAD值有自然下降的趋势,但差异不显著,倒3叶和倒4叶的SPAD值在处理前后12d间的差异达到极显著水平。渍水时间达到12d以上,考察倒2叶的SPAD值即可判断受害程度,渍水时间小于12d以下,考察倒3叶的SPAD值为佳。倒3叶~倒4叶的SPAD值渍害指数和产量的相关关系相对较大,因而在进行小麦不同品种耐渍性比较试验时,选择测定倒3叶~倒4叶的SPAD值,才能得到较好的不同品种间耐渍性差异。

Responses of Chlorophyll Fluorescence and Carotenoids Biosynthesis to High Light Stress in Rice Seedling Leaves at Different Leaf Position

In the present study, we investigated the changes of photosynthesis, chlorophyll fluorescence and the content of carotenoid pigments in rice (Oryza sativa L.) seedling leaves and their responses to high light. The results showed that the rate of photosynthesis, the contents of individual and total carotenoids and the pool size of xanthophyll cycle decreased with age increasing of the leaf. When the leaves were exposed to high light for 2 h, the qN of mature leaf (5th leaf) increased more significantly than that of younger (6th leaf) and older leaves (3rd and 4th leaf). Comparing with the leaves before exposure to high light, the excitation pressure on PSⅡ (1- qP ) increased by 44%, 57%, 19% and 45% in the 3rd, 4th, 5th and 6th leaf under high light, respectively. The highest content of carotenoids and the greatest conversion of violaxanthin to zeaxanthin were found in the 5th leaf, and it was consistent with the 5th leaf exhibiting the strongest resistance to high light. Our results suggested that the ability of rice leaf to resist photoinhibition is related to the level of carotenoids and the ability of carotenoids biosynthesis.

Gas–liquid hydrodynamics in a vessel stirred by dual dislocated-blade Rushton impellers

Towards the objective of improving the gas dispersion performance, the dislocated-blade Rushton impeller was applied to the gas-liquid mixing in a baffled stirred vessel. The flow field, gas hold-up, dissolved oxygen, power consumption before and after gassing were studied using the computational fluid dynamics （CFD） technique. Dispersion of gas in the liquid was modelled using the Eulerian-Eulerian approach along with the dispersed k-e turbulent model. Rotation of the impeller was simulated with the multiple reference frame method. A modified drag coefficient which includes the effect of turbulence was used to account for the momentum exchange. The predictions were compared with their counterparts of the standard Rushton impeller and were validated with the experimental results. It is concluded that the dislocated-blade Rushton impeller is superior to the standard Rushton impeller in the gas-liquid mixing operation, and the findings obtained here lay the basis of its application in process industries.

Effects of the short blade locations on the anti-cavitation performance of the splitter-bladed inducer and the pump

In order to evaluate the effects of the short blade locations on the anti-cavitation performance of the splittel bladed inducer and the pump, 5 inducers with different short blade locations are designed, Cavitation simulatior and experimental tests of the pumps with these inducers are carried out. The algebraic slip mixture model in th CFX software is adopted for cavitation simulation. The results show that there is a vortex at the inlet of the indu（ er. Asymmetric cavitation on the inducer and on the impeller is observed. The analysis shows that the short blad locations have a minor effect on the internal flow field in the inducer and on the external performance of th pump, but have a significant effect on the anti-cavitation performance. It is suggested that the inducer shoul be designed appropriately. The present simulations found an optimal inducer with better anti-cavitatio performance.

Analysis of Growth Laws of Leaves of Flue-cured Tobacco in Various Periods

The growth laws of leaves of flue-cured tobacco in different positions in various periods were summarized. The results showed that the growth speed of new leaves of flue-cured tobacco increased constantly until their growth was the fastest, and then it reduced irreversibly. The length and width of leaves in each position increased fastest when they grew depending on photosynthates instead of or- ganic compounds from functional leaves. Therefore, it is concluded that the increases of leaf length, width and area, and dry matter, and the peak of photosynthetic rate appear successively during the process of leaves of flue-cured tobacco, and the leaf area correction coefficient of leaves of flue-cured tobacco is related to the shape of leaves, which are affected by leaf position and the variety of flue-cured tobacco. The study can provide scientific reference for further research on the growth laws of leaves of flue-cured tobacco.

Effects of leaf age,elevation and light conditions on photosynthesis and leaf traits in saplings of two evergreen conifers,Abies veitchii and A.mariesii

Aims Subalpine coniferous species are distributed over a wide range of elevations in which they must contend with stressful conditions,such as high elevations and extended periods of darkness.Two evergreen coniferous species,Abies veitchii and Abies mariesii,dominate at low and high elevations,respectively,in the subalpine zone,central Japan.The aim of this study is to examine the effects of leaf age,elevation and light conditions on photosynthetic rates through changes in morphological and physiological leaf traits in the two species.Methods We here examined effects of leaf age,elevation and light conditions on photosynthesis,and leaf traits in A.veitchii and A.mariesii.Saplings of the two conifers were sampled in the understory and canopy gaps at their lower(1600 m)and upper(2300 m)distribution limits.Important Findings The two species showed similar responses to leaf age and different responses to elevation and light conditions in photosynthesis and leaf traits.The maximum photosynthetic rate of A.veitchii is correlated negatively with leaf mass per area(LMA)and non-structural carbohydrate(NSC)concentration.LMA increased at high elevations in the two species,whereas NSC concentrations increased only in A.veitchii.Therefore,the maximum photosynthetic rate of A.veitchii decreased at high elevations.Furthermore,maximum photosynthetic rates correlate positively with nitrogen concentration in both species.In the understory,leaf nitrogen concentrations decreased and increased in A.veitchii and A.mariesii,respectively.LMA decreased and the chlorophyll-to-nitrogen ratio increased in understory conditions only for A.mariesii,suggesting it has a higher light-capture efficiency in dark conditions than does A.veitchii.This study concluded that A.mariesii has more shade-tolerant photosynthetic and leaf traits and its photosynthetic rate is less affected by elevation compared with A.veitchii,allowing A.mariesii to survive in the understory and to dominate at high elevations.