Response of Leaf Photosynthesis to Vapor Pressure Difference in Rice (Oryza sativa L) Varieties in Relation to Stomatal and Leaf Internal Conductance

Abstract

In the afternoon when air humidity decreases, leaf photosynthetic rate (P_n) often declines in rice grown under irrigated conditions. To clarify the genotypic difference of P_n in response to humidity, we measured P_n and stomatal conductance (g_s) for nine rice varieties with diverse genetic backgrounds, at various vapor pressure differences (VPD) and developmental stages. P_n and g_s of all the varieties decreased with VPD increase from 1.0 to 2.3 kPa of VPD. The variety with high g_s at low VPD exhibited a greater decline of g_s with VPD increase than the variety with low g_s, but cv. Takanari showed the highest g_s under altered VPD conditions. Significant logarithmic relations were found between the decreased P_n and g_s at the respective developmental stages, suggesting that g_s is the dominant factor determining P_n and its response to VPD change. To explicate the effect of decreased g_s on P_n, we analyzed the relations by using the model that accurately estimated the genotypic difference in P_n at a low VPD with g_s and leaf nitrogen content per unit leaf area in the previous study. The model assuming that leaf internal conductance (g_w) remains unchanged well explained the decreased P_n at high VPDs by g_s change alone. The analysis also suggested the constancy of g_w and carboxylation capacity at high VPD. It is concluded that the genotypic difference in the decrease of P_n at a high VPD is brought mainly by that in decreased g_s, and the varieties with a high g_s always exhibit a high P_n owing to their relatively high g_s at either high or low VPD environments.     

Effects of Soil Moisture Conditions before Heading on Growth of Wheat Plants under Drought Conditions in the Ripening Stage: Insufficient Soil Moisture Conditions before Heading Render Wheat Plants More Resistant to Drought during Ripening

Abstract

Plants growing on soil with insufficient moisture need deep and dense roots to avoid water stress. In crop plants, the production of dry matter during ripening of grains is critically important for grain yield. We postulated that shoot growth would be suppressed but root growth would continue under an insufficient soil moisture condition before heading, while shoot growth would be more vigorous than root growth under a sufficient soil moisture condition. We anticipated that the plants growing under an insufficient soil moisture condition before heading would produce more dry matter and grain under an insufficient soil moisture condition during ripening. In order to examine our hypotheses and to determine the fundamental conditions for improving grain yield and efficient use of irrigated water under limited irrigation, we grew wheat plants (Triticum aestivum L., cv. Ayahikari) in pots (30 cm in diameter, 150 cm in height) with insufficient soil moisture (PD-D pots) or sufficient soil moisture (PW-D pots) for six weeks before heading followed by full irrigation, and then insufficient soil moisture condition during ripening. The growth of shoots was suppressed significantly but that of roots was not before heading in PD-D plants, with a higher resultant ratio of root to shoot than in PW-D plants. The former retained a high leaf water potential and, therefore, were able to produce more dry matter and grain during soil moisture depletion during ripening as compared with the latter plants. We also obtained similar results with field-grown plants.     

滴灌春小麦根系形态特征及内源激素含量对花期干旱及复水的响应

为探明北疆地区不同抗旱性滴灌春小麦品种根系形态及内源激素在开花期干旱后复水过程中的变化特征及其与生物量的关系,以春小麦耐旱性强品种新春6号和耐旱性弱品种新春22号为材料,在土柱栽培下设置常规灌溉（CK）、开花期轻度干旱和中度干旱3种水分条件,分析了干旱胁迫后复水条件下不同耐旱性小麦品种根系形态特征、渗透调节物质及内源激素和生物量的差异。结果表明,两个品种的根长密度（RLD）、根体积密度（RVD）、根表面积密度（RSAD）、可溶性糖（SS）含量、脯氨酸（Pro）含量、生长素（IAA）含量、赤霉素（GA₃）含量、玉米素（ZT）含量、地上部干物质积累量（SDM）以及产量均在干旱复水后随时间呈先增后降趋势,以轻度干旱后复水条件下表现最佳。两个品种比较,在轻度干旱后复水条件下新春6号的RLD、RVD、RSAD、SS含量、Pro含量、IAA含量、GA₃含量、ZT含量、ABA含量、SDM及产量较新春22号平均高出3.38%、4.30%、4.29%、21.84%、10.81%、5.99%、10.02%、16.05%、3.13%、6.86%和3.47%。经相关分析,两个品种于各处理下的RLD、RVD、RSAD、SS含量、Pro含量与IAA含量、GA₃含量和ZT含量间均呈显著正相关,与ABA含量呈显著负相关。综上所述,较优的根系生长及生理代谢是春小麦具有较高抗旱性的原因;轻度干旱后复水可调节滴灌春小麦根系渗透调节物质和内源激素含量变化,进而优化根系形态,促进干物质向穗部转运及产量形成,可作为新疆滴灌春小麦灌溉模式。     

不同秸秆覆盖模式下小麦植株性状、光合及产量的差异

为筛选适合小麦高产栽培的最佳秸秆覆盖模式,设置7种覆盖模式即M0(覆盖量0kg·hm-2)、M1(覆盖量4 000kg·hm-2,隔行覆盖)、M2(覆盖量4 000kg·hm-2,每行覆盖)、M3(覆盖量8 000kg·hm-2,隔行覆盖)、M4(覆盖量8 000kg·hm-2,每行覆盖)、M5(覆盖量12 000kg·hm-2,隔行覆盖)和M6(覆盖量12 000kg·hm-2,每行覆盖),分析了不同秸秆覆盖模式下小麦植株性状、光合及产量的差异。结果表明,适当增加秸秆覆盖量有利于增加小麦节间长和株高,且相同覆盖量下,每行覆盖处理的节间长和株高大于隔行覆盖处理,且M2与M1及M5与M6间株高差异显著。M2、M3、M4、M5和M6孕穗期和灌浆中期的单茎干物质积累量显著高于M0。适宜秸秆覆盖量与不覆盖相比可显著增加旗叶长宽和叶面积;相同覆盖量下,每行覆盖与隔行覆盖间旗叶长宽差异不显著,而灌浆中期旗叶面积间差异显著。秸秆覆盖相对于不覆盖及相同覆盖量下每行覆盖相对于隔行覆盖均有利于提高小麦叶绿素荧光参数Fm、Fv/Fm、ΦPSII和ETR,而降低Fo。M4的光合速率、气孔导度和蒸腾速率数值最高,比M0分别显著增加了25.5%、45.6%和26.4%,且相同覆盖量下每行覆盖相对于隔行覆盖更利于光合速率的提高。未覆盖M0的产量最低(7 846.00kg·hm-2),M4的产量最高(8 408.03kg·hm-2);相同覆盖量下,M2比M1、M4比M3、M6比M5的产量分别增加了1.6%、1.4%和1.2%。小麦单茎干物质积累量、旗叶面积、实际光化学效率、光合速率皆与产量呈线性正相关。以上结果说明,秸秆覆盖量过高和过低及隔行覆盖皆不利于小麦植株生长、光合改善及产量提高,每行覆盖、秸秆覆盖量8 000kg·hm-2是安徽淮北地区小麦适宜秸秆覆盖模式。     

不同耐性玉米自交系苗期根系对低钾胁迫的生物学响应

通过水培试验,以典型耐低钾玉米自交系90-21-3和低钾敏感玉米自交系835为试材,分别于4、6、7、9和10叶期测定玉米根形态、根系还原力、伤流量和干物质积累量,研究不同耐性玉米自交系苗期根系对低钾胁迫的生物学响应。结果表明,低钾胁迫下,耐低钾玉米自交系90-21-3表现为根长增幅大,根表面积、根体积降幅小,根平均直径降幅大。与低钾敏感玉米自交系835相比,低钾胁迫下耐低钾玉米自交系90-21-3的根系相对发达、根系活力强、伤流量大及干物质积累量较大。     

Effects of Low Root Temperature on Dry Matter Production and Root Water Uptake in Rice Plants

Abstract

Chilling is a major constraint in rice production in cool climates. In rice (Oryza sativa L.) plants, both the air temperature and the water (soil) temperature affect various growth processes independently, and low root zone temperature (thus, root temperature) can inhibit rice growth and yield. In this study, we investigated the effect of low root temperature on rice growth in relation to dry matter production and root water uptake. Plants were grown in hydroponic solutions at two temperatures, one equivalent to air temperature and the other 14ºC for 15 d starting 11 d after germination. Low temperature of the solution (low root temperature) inhibited dry matter production of rice plants by decreasing leaf area rather than photosynthetic rate. The response of leaf area was affected by changes in plant water status, that is relative water content (RWC) of stem was decreased by low root temperature resulting in reduced leaf area. The decrease in RWC caused by low root temperature was related to that in root hydraulic conductance (K_r). The responses of transpiration (E) and K_r to the low root temperature depended more on root surface area than on changes in hydraulic conductance per unit root surface area (Lp_r). These results suggest that dry matter production under the low root temperature condition is controlled mainly by quantitative growth parameters such as leaf area and root surface area.     

氮肥对不同品质基因型大豆光合生理和干物质积累的影响

以6个不同品质基因型大豆品种为试材,探讨了苗期追施尿素对叶片光合生理和植株干物质积累的影响。结果表明:随着生育进程,各品种的叶面积指数、叶色值和光合速率呈单峰曲线变化,干物质积累呈"S"型曲线。苗期追施尿素会对开花期至鼓粒初期大豆的叶面积指数、光合速率和叶色值产生显著影响,单株干物质积累最大速率和平均速率在施肥处理间均存在极显著差异。追施氮肥会使单株干物质最大积累速率出现时间提前,以高蛋白品种提前天数最多。     

Zn~(2 )对小麦幼苗干物质及Zn积累的影响

为了探明Zn在小麦植株中的吸收、分配和积累规律,以小麦品种长5864为供试材料,采用室内水培方法,于培养4~13 d后取幼芽和幼根,用原子吸收分光光度计法测定样品中Zn的含量,研究了不同Zn2 供应水平(0、306、0 mg.L-1,分别用Zn0、Zn30、Zn60表示)对小麦幼苗干物质积累及幼苗Zn含量和积累的影响,分析了小麦幼苗中Zn的积累规律。结果表明,外源Zn2 供应可显著提高幼苗根和芽的干重,对小麦幼苗根的影响大于对芽的影响,根对Zn2 更为敏感。外源Zn2 供应能明显提高小麦幼苗根和芽中Zn的含量和积累量。Zn30处理有利于根的生长,能显著提高根中Zn的含量并促进Zn在根中的积累;Zn60处理有利于芽的生长,能显著提高芽中的Zn含量并促进Zn在芽中的积累。     

密度对大豆群体叶面积指数及干物质积累分配的影响

在大田条件下,以垦农4号为材料,研究了大豆在5种密度条件下的叶面积指数及干物质积累分配规律.结果表明:叶面积指数在一定密度范围内随密度增加呈增加趋势,R5期叶面积指数主要集中在冠层中上部;干物质阶段积累量、日积累量以及阶段积累量占总积累量的比例.均呈单峰曲线变化.干物质阶段积累量随密度的增加而增加,单株干物质日积累量随...     

不同春玉米品种干物质生产和子粒灌浆对种植密度的响应

以中单909(ZD909)、吉单209(JD209)和内单4号(ND4)为材料,设置5个种植密度,研究不同种植密度下春玉米子粒产量、干物质积累和灌浆特性的响应特征。结果表明,3个品种的子粒产量均随种植密度提高呈先增加后下降趋势,ZD909在各密度下的产量均高于JD209和ND4。ZD909在9.00万株/hm2下达到最高产量,JD209和ND4在6.75万株/hm2下达到最高产量。群体干物质积累量随密度增加而显著提高,但收获指数呈下降趋势。随密度的提高,ZD909的干物质递增幅度高于JD209和ND4,收获指数下降幅度小于后两个品种。子粒最大灌浆速率、灌浆持续时间均随种植密度的增大而减小,ZD909灌浆持续期、活跃灌浆期均显著长于JD209和ND4。ZD909的生产力受种植密度的不利影响程度低于JD209和ND4,密植增产潜力大。     

Genotypic Variation of Stomatal Conductance in Relation to Stomatal Density and Length in Rice (Oryza sativa L.)

Abstract

Stomatal conductance (g_s) is an important trait responsible for the genotypic difference in gas diffusion for photosynthesis and transpiration in rice (Oryza sativa L.). We measured g_s, stomatal density and stomatal length (guard-cell length) at two weeks before heading for 64 accessions from a rice diversity research set of germplasm (RDRS) and for three high-yielding cultivars (HYC) under field conditions. Considerable variations in g_s, and stomatal length were observed among varieties in RDRS, and it was considered that RDRS covers the species diversity of the stomatal characteristics in rice. When it was compared among the varieties with similar plant earliness, g_s was higher in HYC than in most varieties of RDRS. Stomatal density did not correlate with g_s, and there was a negative correlation between stomatal density and stomatal length. However, noticeable variance existed in the latter relation, where HYC exhibited a higher stomatal density and slightly shorter stomatal length than RDRS. High g_s in HYC is attributable to their high stomatal density and moderate specific stomatal conductance (g_s / stomatal density) while the high-g_s varieties in RDRS tended to have a lower stomatal density and higher specific stomatal conductance. Stomatal length is related to specific stomatal conductance, but there are remarkable differences between these traits. Specific stomatal conductance in HYC has not reached the upper limit for their stomatal size, which raises a possibility of further improvement of HYC in g_s.     

剪叶对豫农202籽粒灌浆与干物质积累的影响

为了探讨小麦新品种豫农202植株上部三片叶对籽粒干物质积累的影响,分别在小麦开花期和灌浆中期进行了不同的剪叶处理,分析了不同剪叶处理对剩余叶片的SPAD值、籽粒灌浆速率及籽粒干物质积累量的影响。结果表明,小麦开花期和灌浆中期剪叶后,植株上部三片叶的SPAD值在不同处理间具有明显差异,剪去部分叶片后剩余叶片的SPAD值均有所提高。从剪叶对籽粒灌浆速率和干物质积累量的影响来看,开花期剪叶的影响程度显著大于灌浆中期剪叶。不同剪叶处理间籽粒的灌浆速率和干物质积累量存在明显差异,开花期剪去倒一叶对灌浆速率具有较大的负向效应,其干物质积累量比对照降低了21.22%;剪去倒三叶对灌浆速率具有较大的正向效应,其干物质积累量增加了12.20%。灌浆中期剪叶后,所有剪叶处理的籽粒灌浆速率和干物质积累量均低于对照,且剪去的叶片越多灌浆速率和干物质积累量下降的幅度越大,同时剪去倒一叶和倒二后下降的幅度最大。     

Leaf gas exchange, chloroplastic pigments and dry matter accumulation in castor bean (Ricinus communis L) seedlings subjected to salt stress conditions

Brazilian castor bean (Ricinus communis L) crops have expanded towards semiarid lands, in which soil salinity is an important factor limiting plant development. In order to evaluate the effects of salt stress on leaf gas exchange, pigments, and dry matter accumulation of seedlings, seeds of castor bean var. BRS Nordestina were planted in 15-L pots filled with 13 kg of soil (control) or with soil plus 2 g NaCl kg⁻¹ soil corresponding to 30 mM NaCl (salt treatment). Seedlings were grown under greenhouse conditions and the effects of salinity were assessed by measuring physiological parameters at 38 and 59 days after germination. Salt treatment induced decreases in leaf water potential at pre-dawn (ψ_pd, 42%), stomatal conductance to water vapor (g_s, 36%), and net carbon assimilation rate (A, 24%) only at 38 days after germination. At the same time, the values for transpiration rate were unchanged and the hydraulic conductance was increased (34%). After 59 days under hypersalinity, leaf ψ_pd increased to −0.44 MPa, although g_s, A, transpiration rate, and hydraulic conductance were not different between treatments. Salt stress effects on chlorophyll a, chlorophyll b and chlorophyll a + b contents were evident only on experimental day 59. The dry matter accumulation of leaves, roots and stems, as well as the total dry matter, and the root to above ground ratio increased with plant growth in both treatments, however, these parameters were lowered in salt-stressed seedlings. In short, all physiological variables were more drastically affected after 38 days under high salinity, and despite acclimatization of A after 59 days exposure to salt, no recovery of the dry matter accumulation was observed in the seedlings, suggesting that this species does not tolerate salt stress at its initial growth stages.     

遮荫胁迫对渍水条件下玉米自交系农艺性状及干物质积累的影响

采用大田试验方法,在大喇叭口期对渍水条件下的36个玉米自交系玉米进行50%遮荫和不遮荫处理,研究遮荫胁迫对自交系农艺性状及干物质积累的影响,对自交系的耐阴性进行评价。结果表明,渍水条件下的玉米自交系遮荫后雌雄间隔期延长,穗位叶叶绿素含量显著增加,地上部干物质显著减少,16个自交系的雄穗主轴长度显著降低,大部分自交系的雄穗分支数无显著变化,株高、穗位高变化不一致。雌雄间隔期延长天数与地上部干物质量减少的百分率呈极显著相关。以雌雄间隔期延长天数与地上部干物质量减少的百分率为主要指标,筛选出11个耐阴性强且具有一定耐涝性的自交系LH01、LH04、LH14、LH17、LH21、LH23、LH24、LH27、LH28、LH32、LH33,可作为豫中南阴雨寡照地区的基础育种材料。     

不同类型夏玉米主要性状及产量的分析

以4种不同类型的夏玉米品种为材料,研究了不同时期其主要性状、干物质积累和分配及产量。结果表明：4种类型夏玉米的产量存在显著差异,在不同密度下产量也表现显著差异,其中大株特大穗型玉米品种CF2187的产量最高,具有相当大的生产潜力;4种类型夏玉米的LAI发展受密度和株型影响,高密度较低密度拥有更大的LAI及持续期,大株大穗型玉米品种的叶面积持续期最长;大株大穗型玉米品种的干物质积累最多,中株中大穗型玉米品种的经济系数最大。     

深松对夏玉米物质生产、光合性能及根系生长的影响

以郑单958为试验材料,设播前深松、4叶期深松处理,以黄淮海地区普遍采用的免耕直播作为对照,分析玉米全生育时期内叶面积指数、净光合速率、叶面积持续期、干物质积累、相对生长率、根系性状以及产量及其构成因素的变化。结果表明,两种深松方式对比,物质生产、光合性能及根系生长方面均差异显著。与免耕直播相比,播前深松可以显著提高玉米拔节期叶面积指数,有效提高吐丝期净光合速率,显著增加拔节期干物重、吐丝期0~100 cm根系总干重以及20~30 cm土层内根系的活力;叶面积持续期、净同化率与相对生长率变化幅度不大。4叶期深松则导致植株的各方面表现较差,营养生长受到限制,叶源不足,叶片早衰。与对照(免耕直播)比较,播前深松增产1.7%,4叶期深松减产11.5%,两种深松方式间差异显著。夏玉米区播前深松具有提升玉米产量的优势,4叶期深松则限制了玉米生长和产量提升。     

不同水分管理模式和播后镇压对小麦干物质积累及产量的影响

为明确不同水分管理模式和播种后镇压对小麦干物质积累及产量形成的影响,以烟农19为材料,在大田条件下设置雨养(RI)、雨养+播后镇压(RC)、传统漫灌(TI)、传统漫灌+播后镇压(TC)、微喷灌(MI)和微喷灌+播后镇压(MC)处理,研究不同处理对小麦干物质积累及产量的影响。结果表明,与RI和TI处理比较,MI处理产量分别提高了44.2%和11.0%;RI处理产量最低,是由于穗数、穗粒数和粒重的显著下降所致,而TI处理产量较MI处理下降是由穗粒数和粒重显著降低导致。雨养和传统漫灌下播后镇压较其未镇压处理显著提升了产量,分别提高14.1%和6.2%。与TI和RI处理比较,MI处理开花期和灌浆期具有较高的群体叶面积指数(LAI)、旗叶叶绿素含量(SPAD值),籽粒平均灌浆速率和成熟期干物质积累量;相比未镇压处理,镇压后,雨养和传统漫灌下LAI提升,雨养和微喷灌处理下灌浆期旗叶SPAD值显著增加,籽粒灌浆速率提高,从而促进了粒重增加和群体干物质积累。总之,微喷灌+播后镇压能促进小麦群体的形成,延缓叶片衰老,提高小麦的穗粒数及千粒重,从而增加小麦产量,为试验区推荐小麦栽培模式。     

高产优质小麦新品种西农979叶面积、叶绿素含量及干物质积累的特点

为了解小麦新品种西农979的叶片功能、干物质积累及运转等特点,为其优质高产高效标准化栽培提供依据,选用西农979及大穗品系西农9814为试验材料,以小偃22为对照,对其不同生长发育时期叶面积、叶绿素含量及干物质的变化规律进行了研究。结果表明,在抽穗期,西农979最大单茎叶面积为72.78cm2,对照小偃22最大单茎叶面积为101.69 cm2;西农979叶片衰老较快,在5月25日几乎没有绿叶面积,而对照小偃22绿叶延迟至6月1日;西农979旗叶叶绿素含量也比对照小偃22低,但西农979单茎干物质积累和对照小偃22相当;在灌浆成熟期,西农979单粒重显著高于对照,成熟后西农979比对照增产7.4%。由此说明西农979叶片光合速率高,开花后光合产物向籽粒中运转快。后期光合时间短是西农979生产上存在的主要问题,可在扬花期采取叶面喷肥来延缓叶片衰老,维持后期叶片光合功能,扩大花后干物质积累量。     

低温对小麦幼苗干物质积累及根系分泌物的影响

为了解小麦干物质积累和根系分泌物变化与小麦抗寒性的关系,采用盆栽方法,以弱春性小麦品种兰考矮早八、偃展4110和半冬性小麦品种豫麦49-198、周麦18为材料,设置4个不同温度处理(T1:昼夜均为18℃;T2:昼夜分别为12℃/7℃;T3:昼夜均为4℃;T4:昼夜均为-10±3℃),研究了低温对小麦幼苗干物质积累、根系分泌物和相对电导率的影响。结果表明,低温胁迫2 d,小麦根系分泌物中可溶性蛋白、可溶性糖及总酚含量升高;低温胁迫3 d,T3处理下,小麦根系分泌物中游离氨基酸和总酚含量较高,T4处理下小麦根系分泌物中可溶性蛋白、游离氨基酸及总酚含量均表现最低,而可溶性糖含量较高。低温胁迫下,根系相对电导率升高,其中豫麦49-198升幅最小,而兰考矮早八升幅最大。低温胁迫下,小麦幼苗干物质积累受到抑制。T3处理下,豫麦49-198干物质积累及幼苗相对生长速率均较高。在4个小麦品种中,豫麦49-198抗寒性较强,兰考矮早八抗寒性较弱。     

不同种植密度下东北春玉米根系特征及其干物质积累的差异比较

以郑单958和先玉335为供试品种,对45 000、67 500和90000株/hm2种植密度下春玉米关键生育期0～60 cm土体根系的主要形态指标及其干物质积累进行分析.结果表明,随密度提高,0～ 60 cm土体中玉米单株根系生物量积累下降,但群体根系总生物量呈上升趋势.3个密度下,从拔节期至乳熟阶段郑单958玉米根系的根长、根表面积、根体积与根长密度均随生育进程呈单峰曲线变化,在抽雄吐丝期达最大值;先玉335根系的相应形态指标从拔节期至乳熟阶段呈下降趋势,在拔节期最大.抽雄吐丝期和乳熟期,两个品种的单株根长、根表面积和根体积随密度增加而下降,但群体的总根长、根表面积、根体积和根长密度随密度的增加而增大.