A comparison of cardinal temperatures estimated by linear and nonlinear models for germination and bulb growth of forage brassicas

Forage brassicas are widely used as a supplementary feed in temperate pasture systems but there is a lack of quantitative data about their growth and development. Furthermore, numerous models are available to estimate cardinal temperatures but there is uncertainty about whether linear or nonlinear models should be used. Initially a germination experiment was used to describe the rate response of nine forage brassicas to temperature. Three models were compared to estimate cardinal temperatures and the two best models were used for thermal time (Tt) accumulation for three groups of forage brassicas. Cardinal temperatures, defined as the base (T_b), optimum (T_opt) and maximum (T_m), differed among groups of species for the bilinear and Lactin models but were similar within a group of species for these models. In most cases, cardinal temperatures estimated by the bilinear and Lactin models for the B. rapa group ranged from 3 to 4 °C for T_b, 31 °C for T_opt and 41 to 48 °C for T_m. For the B. napus and B. napus biennis groups these temperatures ranged from 0 to 3 °C for T_b, 29 to 33 °C for T_opt and 38 °C for T_m. The B. oleracea group had temperatures from 0 to 1 °C for T_b, 25 to 27 °C for T_opt and 35 °C for T_m. A second data set based on hypocotyl thickening was used to estimate the base temperature (T_b) for bulb growth of turnips and swedes. Both models estimated an average T_b of 4.2 °C for bulb turnips and an average of 3.7 °C for swedes. The Lactin model was considered the most adequate model to describe temperature responses where as, in some cases, the bilinear model had to be modified to account for changes in the rate of development. More importantly, an appropriate range of test temperatures was crucial for the estimation of reliable cardinal temperatures, independent of the model used.     

基于叶气温差的生育中期冬小麦水分亏缺诊断研究

为了获取叶片尺度基于叶气温差的冬小麦生育中期水分亏缺诊断阈值,分析了冬小麦叶气温差的典型日变化及其与土壤水分、空气温度及太阳辐射等因子的相互关系,揭示了冬小麦叶气温差对光合气体交换参数的影响,确定了冬小麦叶片水分利用效率较适宜的非气孔限制值及叶气温差范围。结果表明,冬小麦叶气温差在不同的土壤水分条件下表现出不同的日变化规律,随光量子通量增加而升高,随土壤水分、气温增加而降低;4、5和6月冬小麦叶片水分利用效率较适宜的非气孔限制值范围分别为0.7~1.3、1.1~2.0和0.9~1.5,叶气温差控制范围分别为-1.2~0.4、-1.5~-1和-1.25~-0.9℃。     

A calibration method of detecting soil water content based on the information-sharing in wireless sensor network

In agricultural production, there is contradiction between the cost and accuracy of detection during the course of acquiring soil water content (θ) online. This conflict is one of the core issues of automatic water-saving irrigation technology in agriculture. At the same time, capacitive soil moisture sensor (CSMS) has received considerable attention, for it can acquire θ with low cost and high precision, and meet the application requirements of wireless sensor network (WSN). But CSMS is vulnerable to the soil temperature (T_s) and salinity (S_s) in the measurement process. Therefore, this study took EC-5 sensor for example to establish water detection calibration models of soil temperature and salinity for single sensor, using Least Squares Support Vector Machines on MatLAB (LS-SVMlab) as the tool. On this basis, we explored the spatial variability of T_s and S_s, and then a method, which could be used to calibrate the output signals of sensors in multi-point network, was proposed based on the information-sharing (T_s or S_s) technology of WSN. Through laboratory experiment, we effectively reduced the impact of soil temperature and salinity on the single sensor. In example analysis, we investigated the detection precision and costs under different information-sharing radiuses (r). And the results indicated that the method we proposed based on the information-sharing technology of WSN could successfully calibrate the influence of soil temperature and salinity on sensors in multi-point network, and it was an efficacious approach to determine the balance between the calibration accuracy of moisture sensor and the investment of agricultural production. For example, while the calibration precision of soil temperature and salinity is respectively 1%, the costs can be reduced by 30%.     

Efficient reduction of biomass,seed and season long pollen production of common ragweed (Ambrosia artemisiifolia L.)

Ragweed (Ambrosia artemisiifolia L.) is a noxious plant that not only is a troublesome agronomic weed that causes economic damage to agricultural crops but also − and even more importantly − causes severe health problems due to its severe allergenicity. The pollen of invasive ragweed has become a major allergenic risk factor in urban areas in newly occupied regions. Many urban areas prohibit herbicide application; thus, mowing is the most widely used control measure. Counting pollen is labour intensive; therefore, pollen production data are mainly based on estimations. Field experiments were conducted to determine the effects of different mowing scenarios, plant density and cutting height on the biomass, pollen production and seed production of common ragweed plants. Ragweed plants were mown twice: just before the flowering of terminal racemes (BBCH 59) and when the flowers of the re-sprouting lateral shoots reached BBCH 59. A 1- to 3-cm cutting height produced the greatest pollen reduction compared to that of intact control plants (94%) based on a season-long pollen collection. The number of female flowers also significantly decreased (97%). Compared to the control, the onset of pollen discharge was delayed by 5 weeks and the length of the pollen discharge period decreased from 9 to 4 weeks. The season-long unique and reproducible pollen production data can be integrated with airborne pollen modelling and population management strategies.     

自然低温胁迫下3种桉树的叶绿素荧光特性研究

对临安市3种桉树幼苗叶片叶绿素荧光特性进行研究,结果表明,自然低温下,各桉树表现出不同的适应性,总的来说,邓桉>柳桉>巨桉;自然低温(日最低气温-3.6℃)对柳桉和巨桉造成较大损害,而邓桉可通过维持相对较高的光化学效率,以及利用不断增加的qN来进行耗散,具有较强的抵抗低温胁迫伤害的能力。     

湟源县30年0℃活动积温变化特征分析

本文探索了湟源县30年0℃活动积温的变化特征,一是对年际变化特征、高积温年、低积温年进行特征分析;二是将湟源县1987—2016年的0℃活动积温划分为3个10年际进行分析。详细分析内容为不同尺度下的积温最高值、最低值、平均值、极差和距平差。结果表明,30年0℃活动积温整体呈上升趋势,前期11年(1987—1997年)积温均为负距平;中期8年(1998—2005年)积温小幅震荡,后期11年(2006—2016年)积温均为正距平。30年的0℃活动积温平均值为2209.49℃·d,1987年0℃活动积温为最低值1 953.00℃·d;2013年0℃活动积温为最高值2 496.40℃·d。     

Genotypic Variation for Tolerance to Transient Drought During the Reproductive Phase of Brassica rapa

Brassica rapa L. is a genetically diverse parent species of the allotetraploid species, oilseed rape (B. napus) and a potential source of drought tolerance for B. napus. We examined the effect of a 13‐day drought stress period during the early reproductive phase, relative to a well‐watered (WW) control, on subsequent growth and development in nine accessions of B. rapa and one accession of Brassica juncea selected for their wide morphological and genetic diversity. We measured leaf water potential, stomatal conductance, water use, and leaf and bud temperatures during the stress period and aboveground dry weight of total biomass at maturity. Dry weight of seeds and reproductive tissue were not useful measures of drought tolerance due to self‐incompatibility in B. rapa. The relative total biomass (used as the measure of drought tolerance in this study) of the 10 accessions exposed to drought stress ranged from 47 % to 117 % of the WW treatment and was negatively correlated with leaf‐to‐air and bud‐to‐air temperature difference when averaged across the 13‐day stress period. Two wild‐type (B. rapa ssp. sylvestris) accessions had higher relative total and non‐reproductive biomass at maturity and cooler leaves and buds than other types. We conclude that considerable genotypic variation for drought tolerance exists in B. rapa and cooler leaves and buds during a transient drought stress in the early reproductive phase may be a useful screening tool for drought tolerance.     

低温胁迫对蓝莓枝条呼吸作用及生理生化指标的影响

为明确蓝莓枝条不同部位的耐低温能力,利用人工模拟低温胁迫的方法研究了蓝莓1年生枝条尖端、1年生枝条基端和2年生枝条对低温胁迫的生理响应。结果表明:低温胁迫下蓝莓不同部位枝条的各生理指标之间虽然具有一定的相关性,但不同生理指标的相关系数差异较大,即蓝莓枝条不同生理过程对低温的敏感性明显不同。其中,0℃时1年生枝条特别是其尖端的呼吸速率明显高于2年生枝条,但其呼吸作用对低温也特别敏感,当温度降低到-10℃时即均发生明显的降低,且1年生枝条尖端的降低幅度最大。另外,低温胁迫下1年生枝条尖端的丙二醛(MDA)含量和相对电导率增加幅度也明显大于1年生枝条基端和2年生枝条,即1年生枝条尖端对低温胁迫更为敏感。低温胁迫下不同部位枝条虽可以通过增加可溶性糖(SS)和可溶性蛋白(SP)等渗透调节物质,以及增强SOD和POD等抗氧化酶活性的方式来提高其抗寒能力,但当温度降低到-40℃时,不但抑制了蓝莓1年生枝条尖端可溶性蛋白的合成,并且1年生枝条尖端和基端的SOD活性较-20℃时也有不同程度的降低,即-40℃时1年生枝条特别是其尖端蛋白质合成的抑制以及抗氧化酶活性的降低可能是导致其蓝莓在我国北方大兴安岭地区易发生冻、干梢现象的主要原因。而1年生枝条基端和2年生枝条具有较强抗低温能力的原因除了其本身代谢活性较低,对低温不敏感外,低温下有效积累渗透调节物质和增强抗氧化酶的活性在降低其膜质过氧化程度和电解质外渗方面发挥了重要的作用。     

Root zone temperature alters storage root formation and growth of sweetpotato

Large mounds amended with plant residues are a common cultivation method for sweetpotato (Ipomoea batatas) in the western parts of the Papua New Guinea highlands, with a suggested benefit of elevated root zone temperature (RZT) from decomposition. This study aimed to evaluate whether RZT affects the formation and growth of sweetpotato storage roots. Experiments evaluated the effects of a constant elevated RZT on the Beauregard cultivar and of a short‐term increase in RZT on the Beauregard and Northern Star cultivars. Plants were grown in 18‐L pots divided into a control compartment (constant RZT at 20°C) and a treated compartment (RZT at 30, 40 or 50°C). Constant elevated RZT was maintained until harvest, while short‐term increase in RZT occurred in weeks 2 and 3 only. Constant elevated RZT did not affect the total number of storage roots, but RZT of 30°C and above reduced the dry‐biomass of storage roots. The short‐term increase in RZT did not alter the total number or dry‐biomass of storage roots in Beauregard, while both of these attributes were reduced at RZT of 40°C or above in Northern Star. Elevated RZT inhibited dry‐biomass accumulation of storage root, with a more pronounced impact at constant elevated RZT. These results demonstrate that any benefits of the mound culture on sweetpotato yield production do not arise through the influence of temperature elevation.     

超甜玉米子粒果皮柔嫩度的变化规律

为了探讨超甜玉米果皮柔嫩度在子粒发育进程中的变化规律,以10份超甜玉米自交系为材料,采用硬度计法测定子粒发育过程中果皮柔嫩度值,分析果皮柔嫩度在不同环境条件下的变化。结果表明,10份参试材料在果皮柔嫩度上存在梯度差异,其中PE10果皮柔嫩性最好,T105中等,S33205最差;在湖北武汉(2014年春)、海南陵水(2014年冬)两种环境下,在授粉后第12~24天,PE10、T105、S33205的果皮柔嫩度值均呈上升趋势,且各测定时间点的柔嫩度均值由大到小的顺序均为S33205、T105、PE10;随着子粒的发育,相同材料在不同环境条件下果皮柔嫩度差异呈现先增大后缩小最后又趋于一致的规律;2014年湖北武汉春季与海南陵水冬季相比,同一材料最适采收期相差4 d,但最适采收期的果皮柔嫩度值差异不显著,说明环境改变会影响果皮嫩度变化速率,但果皮柔嫩度的好坏本质上仍决定于材料本身。