Effect of Light Quality on Developmental Rate of Wheat under Continuous Light at a Constant Temperature

Abstract

The developmental rate of wheat was investigated under continuous light of eight different qualities (in eight plots) obtained by combining three out of four different kinds of fluorescent lamps (white, blue, purplish red and ultraviolet-A) at a constant temperature of 20°C. A Japanese spring wheat var. Norin 61 and a winter wheat var. Shun-yo were used.The number of days from seeding to heading varied extensively with the variety and the light quality. The first heading wasobserved in the plot under three white fluorescent lamps (W + W + W) at 37 and 81 days after seeding in Norin 61 and Shun-yo, respectively. The developmental rate in both cultivars was significantly correlated with the ratio of energy in 500–550 nm range (green light) and 600–700 nm range (red light) to that in the whole spectral range (250–1,000 nm). These results suggest that green and red lights play important roles in the regulation of the developmental rateindependent of photoperiodism and vernalization.     

Response Spectrum for Green Light-Induced Acceleration of Heading in Wheat cv. Norin 61

Abstract

The response spectrum for green light induced-acceleration of heading in wheat cv. Norin 61 was investigated using narrow-bandwidth (10 nm) green light within the range of 520–550 nm. Heading was observed from approximately 30 days after emergence. The earliest heading was observed at 540 nm, which suggests the presence of a green light photoreceptor different from hitherto known photoreceptors.     

调亏灌溉对冬小麦不同生育阶段光合速率的影响

为给冬小麦调亏灌溉（Regulated deficit irrigation,RDI）指标与模式的建立提供理论依据和技术参数,在防雨棚条件下,采用子、母盆栽方法,以冬小麦为试验材料,分析了RDI对冬小麦不同生育阶段光合速率（Pn）的影响,并对其进行了模拟,以探寻适宜的水分调亏阶段（时期）和调节亏水度。结果表明,冬小麦返青至拔节期水分调亏对Pn无显著影响;拔节至抽穗期轻度水分调亏的Pn未受显著影响,复水后补偿效应显著;中、重度调亏的Pn受到显著抑制,复水后虽有补偿效应,但与对照差异不显著;抽穗至灌浆期轻度水分调亏对Pn无显著影响,中、重度水分调亏的Pn受到强烈抑制,复水后补偿效应较弱,补偿时间也有限。据此认为,冬小麦RDI的适宜阶段为拔节期以前,适宜的调亏度为50%～65%FC（Field capacity,FC）;拔节至抽穗和抽穗至灌浆期也可轻度调亏,调亏度为60%～65%FC。     

不同施氮量和栽插密度下三角形强化栽培杂交稻抗倒伏性与群体质量的关系

 以杂交水稻组合Ⅱ优498为材料,在三角形强化栽培(TSRI)条件下,研究了施氮量和栽插密度对水稻群体质量及抗倒伏能力的影响,并探讨了主要群体质量指标与茎秆抗倒伏性及产量间的关系。结果表明,TSRI下,施氮量及栽插密度对水稻产量、群体质量以及茎秆基部各节间抗倒伏能力均存在显著的调控作用。施氮量为150 kg/hm2与栽插规格40 cm×40 cm配合可提高结实期叶面积指数(LAI)、群体透光率,协调茎秆基部各节间弯曲力矩与抗折弯矩,缓和高产栽培的穗粒矛盾,显著提高籽粒产量;而施氮量增加至225 kg/hm2,应适当降低栽插密度,来缓解群体质量指标的恶化,降低倒伏指数,栽插规格50 cm×50 cm为宜。相关性分析表明,不同施氮量和栽插密度下水稻群体质量指标与茎秆基部各节间抗倒伏能力显著或极显著相关;结合产量表现,尤以齐穗期、齐穗后30 d中部的群体透光率以及齐穗后30 d的根系伤流量对水稻产量及抗倒伏性影响显著。     

Microenvironment of a corn–soybean–oat strip intercrop system

The microenvironment of a corn (Zea mays L.)–soybean (Glycine max [L.] Merr.)–oat (Avena sativa L.) narrow strip intercrop system was studied on four farms in Iowa, USA during 1991–1993 (one or two farms studied each year) with the objective of explaining previously observed patterns of strip-crop yields. Air and soil temperatures, humidity, wind, and photosynthetic photon flux density (PPFD) for each row in a strip were recorded continuously during 4–13-day periods several times during each growing season; short-term measurements of light extinction through the corn and soybean canopies were made late in the 1993 growing season. Soybean biomass in September 1993 was also determined. Early in the growing season, there typically were no significant differences among rows within a strip in any environmental or growth variable. Later in the growing season, daily PPFD received varied more across each strip than any other environmental variable measured; the outer side of edge rows of corn in north–south rows typically received significantly higher daily PPFD (2–38% more) than inner rows in the strip, while the outside of the soybean row furthest from corn received 36–140% greater PPFD than the corn-side of the row next to the corn strip. Soybean height; leaf mass per leaf area; and leaf mass, stem mass, and pod mass per unit land area in September were strongly related to daily PPFD, with all except height increasing with greater PPFD. Total biomass increased by 32% from the row closest to corn to the row furthest from corn, although there was no change in the ratio of leaf:stem:pod with row position. Thus, PPFD varied the most across the strips of any environmental variable, and crop growth was closely related to PPFD received.     

Modeling light and temperature effects on leaf emergence in wheat and barley

Phenological development affects canopy structure, radiation interception, and dry matter production; most crop simulation models therefore incorporate leaf emergence rate as a basic parameter. A recent study examined leaf emergence rate as a function of temperature and daylength among wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) cultivars. Leaf emergence rate and phyllochron were modeled as functions of temperature alone, daylength alone, and the interaction between temperature and daylength. The resulting equations contained an unwieldy number of constants. Here we simplify by reducing the constants by > 70%, and show leaf emergence rate as a single response surface with temperature and daylength. In addition, we incorporate the effect of photosynthetic photon flux into the model. Generic fits for wheat and barley show cultivar differences less than +/- 5% for wheat and less than +/- 10% for barley. Barley is more sensitive to daylength changes than wheat for common environmental values of daylength, which may be related to the difference in sensitivity to daylength between spring and winter cultivars. Differences in leaf emergence rate between cultivars can be incorporated into the model by means of a single, nondimensional factor for each cultivar.     

小麦抗吸浆虫特性与主要农艺性状的相关分析

为给小麦抗吸浆虫育种提供参考,以小麦高抗和高感吸浆虫品种构建的重组自交系为材料,分析了小麦形态特征、抽穗期和开花期与吸浆虫侵害后小麦估计损失率的相关性。结果表明,吸浆虫侵害后,小麦估计损失率与植株高度、穗下茎节间长度呈极显著负相关,相关系数分别为-0.286和-0.178;估计损失率与抽穗度呈显著负相关,相关系数为-0.123;而估计损失率与小穗密度的相关性不大,相关系数仅为-0.026。抽穗期和开花期均与估计损失率呈极显著的正相关,相关系数分别为0.155和0.161;抽穗期至开花期天数与估计损失率的相关性不大,仅为-0.071。因此可以通过株高、穗下茎节间长度、抽穗度、抽穗和开花的时间大致判断小麦对吸浆虫的抗性。     

Duration of the grain-filling period in maize is not affected by photoperiod and incident PPFD during the vegetative phase

Total number of initiated leaves and duration from sowing to silking increases when photoperiod is increased during the photoperiod-sensitive phase in maize (Zea mays L.). Little is known, however, about possible other effects of photoperiod and incident photosynthetic photon flux density (PPFD) on rate of development and duration of life cycle. A study was undertaken to quantify effects of photoperiod and incident PPFD from sowing to the 15-leaf stage on rate of leaf appearance and duration of the grain-filling period. The short-season maize hybrid Pioneer 3902 was grown in growth cabinets from sowing to the 15-leaf stage with either (i) a 10 h photoperiod at high PPFD (650 μmol m⁻² s⁻¹), (ii) a 20 h photoperiod consisting of 10 h of high PPFD followed by 10 h of low PPFD (5–50 μmol m⁻² s⁻¹), or (iii) a 20 h photoperiod of high PPFD. From the 15-leaf stage to maturity the plants were placed under a 16 h photoperiod in a growth room. Increasing photoperiod from 10 to 20 h increased final number of initiated leaves and delayed silking but did not affect rate of leaf appearance. Doubling incident PPFD to a value similar to that under Ontario field conditions during the summer resulted in a 16% increase in rate of leaf appearance and in a significant increase in total number of initiated leaves. Differences in final number of initiated leaves and in rate of leaf appearance from sowing to the 15-leaf stage among treatments resulted in a 4-day difference in silking date between the 10 h photoperiod treatment and the two 20 h photoperiod treatments. Duration of the grain-filling period did not differ among the three treatments.     

Net photosynthetic rate of cocksfoot leaves under continuous and fluctuating shade conditions in the field

Maximum light‐saturated photosynthetic rate (Pmax) and stomatal conductance (gs) of field‐grown cocksfoot (Dactylis glomerata L.) leaves in a silvopastoral system were measured at different times under moderate (850–950 µmol m^?2 s^?1 photosynthetic photon flux density, PPFD) and severe shade (85–95 µmol m^?2 s^?1 PPFD). Also Pmax and gs were measured after 30, 60 and 180 min of severe shade to determine the lag in the rise of photosynthesis rate from low to high irradiance levels (induction state). The highest Pmax and gs values obtained were 26·5 µmol CO₂ m^?2 s^?1 and 0·41 mol H₂O m^?2 s^?1 in non‐limiting conditions with full sunlight (1900 µmol m^?2 s^?1 PPFD). These values were defined as standardized dimensionless Pmax_s=1 and gs_s=1 for comparison of treatment effects. The Pmax_s under severe shade decreased by 0·004 units per minute from 1 to 180 min and reached a steady‐state of 0·37 units after 140 min. Under moderate shade, Pmax_s decreased by 0·002 units per minute from 1 to 120 min and reached a steady‐state of 0·76 units. The time required to reach full induction on return to full sun (Pmax_s=1) was 15 min after 30 min of severe shade and 37 min after 180 min of shade. Mathematical equations were derived to describe the changes in Pmax_s and gs_s under severe and moderate shade and during induction. The rate of change of gs_s was slower than for Pmax_s on entering shade and also slower during the subsequent induction process. This indicated other factors in addition to gs were operating in the reduction and increment of Pmax and a two‐step model to explain this is proposed. The defined photosynthetic responses of cocksfoot leaves to fluctuating light regimes could be used to develop quantitative predictions of Pmax for inclusion in a canopy photosynthesis model of silvopastoral systems.     

A spectral index to monitor the head-emergence of wheat in semi-arid conditions

Harvesting wheat (Triticium aestivum L.) for forage or leaving it for grain is the main decision uncertainty growers face in semi-arid regions during mid-season. To facilitate decision-making, a decision support system (DSS) has recently been proposed that requires information about crop water and nutritional status during spike emergence. Though remote sensing has been used to provide site-specific crop status information, a spectral vegetation index is needed to ensure that the information has been acquired during spike emergence. The objective of this study was to propose a spectral index sensitive to spike emergence and validate its suitability across different commercial farm fields by using ground spectral measurements and multispectral satellite imagery. To develop the index, controlled experiments with commonly grown wheat varieties were conducted during the 2004/2005 and 2005/2006 growing season in the agricultural area of the northern Negev desert of Israel. The experiments showed that spike emergence correlated most strongly (r = 0.7, p < 0.05) with spectral changes near the 1.2 μm water absorption feature in contrast to the band at 1.1 μm which appeared to be only weakly correlated. Thus, the spike emergence sensitive band at 1.2 μm has been combined with the insensitive band at 1.1 μm as reference to form the ratio-based normalized heading index (NHI). Experimental data were then used to establish an index threshold that helps separate data acquired before and after spike emergence. The proposed NHI was able to identify spike emergence with a classification accuracy varying between 53 and 83%. Accuracy was influenced by season, and whether narrow or broad spectral bands were used. Validation of the index in commercial farm fields in Israel and the United States showed that the classification accuracy was similar for ground spectral measurements and the advanced land imager (ALI) satellite imagery. These results suggest that the NHI is suited for identifying the onset of heading throughout wheat-growing areas without the need for characterizing seasonal trends.     

Gas exchange characteristics of wheat stands grown in a closed, controlled environment

Information on gas exchange of crop stands grown in controlled environments is limited, but is vital for assessing the use of crops for human life-support in closed habitats envisioned for space. Two studies were conducted to measure gas exchange of wheat stands (Triticum aestivum L. cv. Yecora Rojo) grown from planting to maturity in a large (20 m2 canopy area), closed growth chamber. Daily rates of dark-period respiration and net photosynthesis of the stand were calculated from rates of CO2 build-up during dark cycles and subsequent CO2 drawdown in the light (i.e., a closed-system approach). Lighting was provided as a 20-h photoperiod by high-pressure sodium lamps, with canopy-level photosynthetic photon flux density (PPFD) ranging from 500 to 800 micromoles m-2 s-1 as canopy height increased. Net photosynthesis rates peaked near 27 micromoles CO2 m-2 s-1 at 25 d after planting, which corresponded closely with stand closure, and then declined slowly with age. Similarly, dark-period respiration rates peaked near 14 micromoles CO2 m-2 s-1 at 25 d and then gradually declined with age. Responses to short-term changes in irradiance after canopy closure indicated the stand light compensation point for photosynthesis to be near 200 micromoles m-2 s-1 PPFD. Tests in which CO2 concentration was raised to approximately 2000 micromoles mol-1 and then allowed to draw down to a compensation point showed that net photosynthesis was nearly saturated at > 1000 micromoles mol-1; below approximately 500 micromoles mol-1, net photosynthesis rates dropped sharply with decreasing CO2. The CO2 compensation point for photosynthesis occurred near 50 micromoles mol-1. Short-term (24 h) temperature tests showed net photosynthesis at 20 degrees C > or = 16 degrees C > 24 degrees C, while dark-period respiration at 24 degrees C > 20 degrees C > 16 degrees C. Rates of stand evapotranspiration peaked near Day 25 and remained relatively constant until about Day 75, after which rates declined slowly. Results from these tests will be used to model the use of plants for CO2 removal, O2 production, and water evaporation for controlled ecological life support systems proposed for extraterrestrial environments.     

小麦秸秆还田条件下轻简栽培水稻的生长特性

 以粳稻品种扬辐粳8号作试验材料,设小麦秸秆还田处理,以秸秆不还田作对照,进行直播、机械插秧、抛秧,并对水稻物质生产、产量形成及有关生理指标进行了分析。与秸秆不还田相比,秸秆还田处理穗数均有所下降,每穗粒数、结实率和千粒重均有所增加,产量均显著提高;各生育期的茎蘖数均明显降低。光合势、叶面积指数和干物质积累抽穗前低于秸秆不还田,抽穗后则相反;各生育期的根冠比均较高。抽穗期高效叶面积、高效叶比例以及粒叶比均较大,结实期茎鞘中贮存的碳水化合物的输出率及转换率以及收获指数明显大于秸秆不还田。结实期根系活力、伤流液、光合速率和ATP酶活性均高于秸秆不还田。阐明了秸秆还田轻简栽培水稻的生育特性和增产效应。同时,对秸秆还田水稻高产的生理原因进行了讨论,并提出秸秆还田水稻的关键调控技术。     

种植密度对匀播冬小麦干物质积累、转运及产量的影响

为探究匀播冬小麦对种植密度的响应,以不同穗型品种新冬22(A_1)和新冬50(A_2)为材料,匀播(株行距相等)条件下设置了123万、156万、204万、278万、400万株·hm~(-2)(分别记为M_1、M_2、M_3、M_4、M_5)5个种植密度,研究了不同种植密度下匀播小麦干物质积累、运转、产量及其构成因素的差异。结果表明,匀播条件下,冬小麦抽穗前干物质积累量随种植密度的增加而增加,抽穗后干物质积累量随种植密度增加先增加后降低;新冬22号花后干物质积累量、花后干物质对籽粒产量贡献率、籽粒产量均表现为M_2处理最高,新冬50号花后干物质积累量、花后干物质对籽粒产量贡献率、籽粒产量均表现为M_4处理最高。随着种植密度的增加,两个品种的有效穗数呈增加趋势,穗粒数、千粒重呈下降趋势,籽粒产量呈先升后降趋势。匀播条件下,多穗型品种新冬22号适宜种植密度为156万株·hm~(-2),大穗型品种新冬50号适宜种植密度为278万株·hm~(-2)。     

两个大豆[Glycine Max（L.）Merril]品种光合作用日变化的研究

对两个大豆品种光合作用日变化的多次测定,结果表明:两个大豆品种的光合速率(A)日变化均呈双峰曲线,气孔阻力(R_s)的日变化与A相反,但中午时的细胞间隙CO_2浓度(Ci)只有轻微的降低,这说明中午A降低的内部因素除气孔限制外,还有非气孔因素的限制。中午时的光量子通量密度(PPFD)和大气温度(Ta)升高,相对湿度(R_H)下降,引起叶片温度(Te)的升高。     

Testing Polarization Measurements with Adjusted View Zenith Angles in Varying Illumination Conditions for Detecting Leaf Orientation of Wheat Canopy

Abstract:

The previous work revealed that the polarization of light reflected from heading wheat canopies allowed the detection of changes in the canopy structure, i.e., the leaf inclination angle. Accordingly, in order to improve measurement accuracy in this study we examined the effects of the solar zenith angle (= 90º–solar elevation) and weather conditions at the time of polarization measurements for the light reflected from wheat canopies that were fertilized by different means. We measured polarization in the 660 nm spectral band from the heading canopies of wheat, which were grown in plots fertilized with a basal dressing and then top-dressed at the jointing and booting stages. The radiometric measurements were carried out at various solar zenith angles: 22º–41º on two proximal days, one overcast and the other clear. An empirical method for the adjustment of view zenith angle, based on the solar position at the time of measurement, was effective for the measurement of the degree of polarization (i.e., ratio of the polarized part of reflected light to the total reflected light energy) to eliminate interference due to the change in solar zenith angle. Although the mean values of polarization degree measured in overcast conditions were significantly lower than those measured under clear conditions, the plots top-dressed at the jointing stage could be detected via the polarized reflected light measured under both conditions of illumination.     

多光谱与热红外数据融合在冬小麦产量估测中的应用

为了解多光谱与热红外数据融合对冬小麦产量估测精度的影响,以30个黄淮麦区冬小麦品种为材料,利用三种灌溉处理（处理1、处理2和处理3灌水量分别为240、190和145 mm）下冬小麦拔节期、挑旗期、抽穗期与灌浆期的无人机多光谱和热红外动态数据,构造了多个光谱指数,以支持向量机构建冬小麦产量估测模型,并验证其精度。结果表明,植被指数与籽粒产量的相关性受溉水量影响,处理1下植被指数与籽粒产量均呈正相关,处理2下植被指数除土壤调整植被指数（SAVI）和转化叶绿素吸收反射指数（TCARI）外均与籽粒产量呈正相关,处理3下植被指数与籽粒产量均呈负相关。通过多光谱和热红外数据融合构建的冬小麦产量估测模型的预测精度比仅使用多光谱数据构建的模型提高8%。不同灌溉条件下,通过多光谱与热红外数据融合构建的模型的预测精度存在差异,在处理1、处理2和处理3下拔节期、挑旗期、抽穗期和灌浆期验证决定系数（R）最高值分别为0.63、0.68和0.56,均方根误差（RMSE）最低值分别为0.60、0.24和0.41 t·hm^-2,且在三种灌溉条件下灌浆期预测效果均最佳。因此,利用无人机光谱对小麦品种产量估测时应将多光谱与热红外数据融合,用支持向量机（SVM）算法构建产量估测模型,且模型在灌浆期具有较高预测  精度。     

The QTL Analysis of RuBisCO in Flag Leaves and Non-Structural Carbohydrates in Leaf Sheaths of Rice Using Chromosome Segment Substitution Lines and Backcross Progeny F2 Populations

Abstract

In rice (Oryza sativa L.), the maintenance of high photosynthetic rate of flag leaves and the carbon remobilization from leaf sheaths after heading is a critical physiological component affecting the yield. To clarify the genetic basis of RuBisCO content of the flag leaf, a major determinant of photosynthetic rate, and non-structural carbohydrate (NSC) concentration in the third leaf sheath at heading, we carried out quantitative trait loci (QTL) analysis with 39 Koshihikari/Kasalath chromosome segment substitution lines (CSSLs) and backcross progeny F₂ population derived from target CSSL holding the QTL/Koshihikari in the field. QTLs for RuBisCO content and NSC concentration at heading were detected between R2447-C1286 and R2447-R716 on chromosome 10, respectively, by comparing Koshihikari with four CSSLs for chromosome 10 (SL-229, -230, -231 and -232). The progeny QTL for RuBisCO content and for NSC concentration at heading qRCH-10 and qNSCLSH-10-1, respectively, were detected at similar marker intervals between RM8201 and RM5708. In addition, QTLs for RuBisCO content at 14 d after heading, qRCAH-10-1 and qRCAH-10-2, were detected in regions different from that of qRCH-10. No QTL for NSC concentration at 14 d after heading was detected between RM8201 and R716, the region analyzed in this study. The QTLs qRCH-10 and qRCAH-10-1 for RuBisCO content would have additive effects. These QTLs for RuBisCO content and NSC concentration newly found using CSSLs and their backcross progeny F₂ population should be useful for better understanding the genetic basis of source and temporary-sink functions in rice and for genetic improvement of Koshihikari in terms of their functions.     

冬小麦不同冠层叶片光合蒸腾和水分利用效率变化特征及对灌溉的响应

为了解冬小麦不同冠层叶片光合和蒸腾作用特征以及随水分条件的变化规律,通过田间试验,以冬小麦京冬22为试验材料,设置0 mm（T₀）、220 mm（T₁）、280 mm（T₂）3种水分处理,比较分析了冬小麦不同冠层叶片净光合速率、蒸腾速率及水分利用效率对光合有效辐射和灌溉响应的差异。结果表明,三种水分处理下,冬小麦不同冠层叶片的蒸腾速率和光合速率随光合有效辐射的增加而增加,随后趋于平缓。不同冠层叶片蒸腾速率、光合速率对光合有效辐射的响应表现为上层>中层>下层;不同冠层叶片WUE对光合有效辐射的响应表现为上中层>下层。光合有效辐射相同时,灌水处理（T₁和T₂）的叶片光合蒸腾速率均高于不灌水处理（T₀）。T₁、T₂处理下,叶片光合速率对光合有效辐射响应在整个生育期内表现为灌浆期>抽穗期>成熟期>拔节期,蒸腾速率对光合有效辐射响应在整个生育期内表现为抽穗期>灌浆期>拔节期>成熟期;T₀处理下,叶片光合速率对光合有效辐射响应在整个生育期内表现为灌浆期>拔节期>抽穗期>成熟期,蒸腾速率对光合有效辐射响应在冬小麦整个生育期内表现不显著。因此,在进行小麦叶片到单株光合蒸腾尺度拓展估算时,应考虑冠层位置和水分条件对拓展结果的影响。     

台湾牛樟在海南引种栽培及生长特性研究

为了在海南成功引种台湾牛樟,以获得适合当地种植、推广的优势树和栽培技术,对半年生台湾牛樟幼苗进行引种栽培试验。研究台湾牛樟幼苗在3种不同郁闭度(郁闭度0、0.3、0.8)和3种基质类型(酸性砖红壤,椰糠+红壤,河沙+红壤)下的成活情况、生长状况。结果表明:台湾牛樟一年3~4次抽稍,属中期生长型,嫩叶与新梢颜色呈棕红、浅绿相间,树体主干分叉生长。在郁闭度0.3条件下,幼苗成活率、保存率为最大值,分别是100%和93.3%;郁闭度0和0.3条件下,2年生台湾牛樟树高、地径、冠幅的总生长量较高,引种表现出良好的适应性和抗逆性;郁闭度0.8黄桐林下套种表现最差;3种基质类型中幼苗成活保存率以"椰糠+红壤"基质最高。说明郁闭度是影响台湾牛樟生长发育的主要因子,栽培基质具有促进其生长发育的作用。      

强化栽培下水稻穗分化期叶片光合速率与水分利用率的研究

 用超级杂交稻两优培九、Ⅱ优7954和国稻1号作为研究材料，比较SRI水稻穗分化期不同移栽密度叶片光合速率和水分利用率。结果表明，SRI水稻稀植后能保持一定的叶面积指数，随着移栽密度从1.95×105丛/hm2下降到0.75×105丛/hm2，群体透光率增加，各叶位(第9叶至第13叶)叶片的光合速率和水分利用率明显提高，蒸腾速率降低，抽穗整齐度下降，第9叶和第10叶的光合速率和水分利用率提高的幅度较大。在试验条件下，水稻强化栽培的产量在移栽密度为165×105丛/hm2 时最高。