CO2浓度倍增对谷子拔节期和灌浆期光合色素含量和PSⅡ功能的影响

研究了CO_2浓度倍增对谷子(Setaria italica (L.)Beauv.)叶片单位鲜重和单位叶面积叶绿素(Chl)和类胡萝卜素(Car)的含量以及PSⅡ功能的影响。结果表明,CO_2浓度倍增能提高拔节期成熟叶片和灌浆期成熟旗叶的Chl和Car的含量,并且能提高这两种叶片PSⅡ反应中心开放部分的比例。然而拔节期叶片和灌浆期旗叶的qN值和PSⅡ总的光化学量子产量,以及 F_v/F_o、F_v/F_m和F_d/F_s的值对CO_2浓度倍增的响应不同,表明CO_2浓度倍增对拔节期叶片光合功能的改善优于灌浆期的旗叶。     

光逆境对叶绿体叶绿素蛋白质复合物的影响

研究了强光照射对菠菜叶绿体的叶绿素蛋白质复合物及一些光合特性的影响。实验结果表明,随着强光照射时间的延长,首先,属光系统Ⅱ核心的叶绿素蛋白质复合物的CPa带明显减少了,进而属LHCII的寡聚体和二聚体的带有了不同程度的降低,最后,包括光系统I在内的叶绿素蛋白质复合物带大部分被分解了。结果还表明,当光逆境还未使叶绿素蛋白质复合物发生明显变化时,代表光系统Ⅱ活性的Fv/Fo值及DCIP光还原活性就已显著地降低了。     

综述: 植物光系统Ⅱ捕光过程的超分子结构基础

光系统Ⅱ(photosystem Ⅱ,PSⅡ)是位于植物、藻类和蓝细菌等放氧光合生物类囊体膜上的重要超分子复合物,它可通过捕获光能用于激发反应中心的电荷分离并驱动电子传递过程,在常温常压下可将水分子裂解产生氧气和质子．植物光系统Ⅱ的外周存在主要和次要捕光复合物Ⅱ(major and minor light-harvesting complex Ⅱ,LHCⅡ),它们负责吸收光能并向光系统Ⅱ传递激发能,并且还参与非光化学淬灭和状态转换相关的捕光调节过程．近年来,围绕光系统Ⅱ和LHCⅡ的结构生物学研究取得了一系列重要进展,本文总结了PSⅡ、LHCⅡ和二者共同组成的PSII-LHCII超级复合物的结构生物学研究历程以及最新进展,并对该领域的未来研究方向做出展望．     

2,4-表油菜素内酯对盐胁迫下黄瓜幼苗叶片光合特性的影响北大核心CSCD

以黄瓜品种’新春4号’为试验材料,研究了在中度盐胁迫(50 mmol/L NaCl)条件下,外源喷施0.01 mg/L 2,4-表油菜素内酯(EBL)和24μmol/L油菜素内酯抑制剂(BZR)处理对盐胁迫下黄瓜幼苗叶片快速叶绿素荧光诱导动力学曲线(OJIP)及相关荧光参数的影响,探讨EBL缓解黄瓜幼苗中度盐胁迫伤害的光合生理机制。结果表明:(1)盐胁迫导致黄瓜幼苗叶片净光合速率(P_(n))、气孔导度(G_(s))、蒸腾速率(T_(r))下降,胞间CO_(2)浓度(C_(i))增加,初始荧光(F_(o))、最大荧光(F_(m))下降,OJIP曲线中J点、I点显著增加,降低了黄瓜幼苗叶片光合性能,且对PSⅡ受体侧的伤害大于供体侧,表现为PSⅡ反应中心损伤,光合电子从Q_(A)向Q_(B)的传递效率降低,电子传递受阻。(2)在50 mmol/L NaCl处理下,外源喷施0.01 mg/L EBL可显著提升NaCl胁迫下黄瓜幼苗叶片P_(n)、G_(s)、T_(r)、光合性能(PI_(ABS)),降低C_(i),显著增加单位面积内吸收(ABS/CS_(m))、捕获(TR_(o)/CS_(m))、用于电子传递(ET_(o)/CS_(m))的光能以及有活性反应中心的数目(RC/CS_(m))。(3)与NaCl+EBL处理相比,NaCl+EBL+BZR处理后黄瓜幼苗叶片光合性能进一步降低,证明EBL对黄瓜幼苗盐胁迫引起的PSⅡ伤害有缓解作用。研究发现,外源喷施适量2,4-表油菜素内酯能有效缓解黄瓜幼苗叶片在盐胁迫条件下受到的光合电子传递链中(PSⅡ)受体侧的伤害,增加电子从Q_(A)向Q_(B)传递的效率,从而显著改善盐胁迫下黄瓜幼苗叶片的光合性能。     

具放氧活性的光系统Ⅱ核心复合物的光谱特性和叶绿素蛋白质成分的研究

我们从菠菜叶片分离出一种具有高放氧活性的光系统Ⅱ(PSII)核心复台物.我们对这种PSII核心复合物进行了PSII光化学活性、吸收、荧光光谱特性和叶绿素蛋白质成分的研究.这种PSII核心复合物是一种不含PSI成分,又除去了LHC-Ⅱ的较纯,较小的具有高放氧活性(?)的单位.在文中对PSII反应中心叶绿素的吸收成分和CPa带进行了一些讨论.     

不同叶龄黄瓜叶片叶绿素蛋白质复合物组分的比较研究

用SDS — 聚丙烯酰胺凝胶电泳的方法,对比分析了老、嫩黄瓜叶片叶绿素蛋白质复合物之间的差异,发现嫩黄瓜叶片中缺少1条属光系统I的CPIb带。从低温荧光发射光谱观察到,嫩黄瓜的光系统I相对高于光系统Ⅱ,而老黄瓜则相反。指出在叶绿体发育过程中首先形成光系统I,以后是光系统Ⅱ。我们还注意到,叶片中的F685/F735比值与叶绿素蛋白质复合物中的单体／寡聚体比值之间呈正相关关系。     

不同叶龄黄瓜叶片叶绿素蛋白质复合物组分的比较研究

用SDS-聚丙烯酰胺凝胶电泳的方法,对比分析了老、嫩黄瓜叶片叶绿素蛋白质复合物之间的差异,发现嫩黄瓜叶片中缺少1条属光系统Ⅰ的CPI_b带。从低温荧光发射光谱观察到,嫩黄瓜的光系统Ⅰ相对高于光系统Ⅱ,而老黄瓜则相反。指出在叶绿体发育过程中首先形式光系统Ⅰ,以后是光系统Ⅱ。我们还注意到,叶片中的F685/F735比值与叶绿素蛋白质复合物中的单体/寡聚体比值之间是正相关关系。     

圆二色光谱揭示光系统Ⅱ在热处理过程中叶绿素荧光动力学变化的原因

研究了光系统Ⅱ(PSⅡ)在热处理过程中的叶绿素a荧光和圆二色(CD)光谱。在30 ℃～40 ℃热处理过程中,PSⅡ的叶绿素荧光参数Fo'保持稳定不变;当温度大于40 ℃时,Fo' 逐渐升高并在55 ℃达到最大值。在PSⅡ颗粒和富含捕光色素(LHCⅡ)的复合物的热处理过程中,具有超大振幅的CD异常信号出现,并且在40 ℃时, 677 nm的异常CD峰强度达到最大。这些结果暗示在PSⅡ颗粒热处理过程中,PSⅡ颗粒中的LHCⅡ的聚集状态和异常CD信号相关,并且也可能是影响Fo'的一个重要因素。     

光逆境对叶绿体叶绿素蛋白质复合物的影响

研究了强光照射对菠菜叶绿体的叶绿素蛋白质复合物及一些光合特性的影响。实验结果表明,随着强光照射时间的延长,首先,属光系统Ⅱ核心的叶绿素蛋白质复合物的ＣＰａ带明显减少了;进而属ＬＨＣＩＩ的寡聚体和二聚体的带有了不同程度的降低;最后,包括光和Ｉ内的叶绿素蛋白质复合物带大部分被分解,结果还表明,当光逆境还未使叶绿素蛋白质复合物发生明显变化时;代表光系统ＩＩ活性的Ｆｖ／Ｆｏ值及ＤＣＩＰ光还原活性就已明显变     

CO2浓度倍增对10种禾本科植物叶片形态结构的影响

在CO_2正常浓度(350μL/L)和倍增(700μL/L)条件下,对小麦(Triticum aestivum L.)、半野生小麦(T.aestivum ssp.tibeticum)、大麦(Hordeum vulgare L.)、野大麦(H.brevisubulatum(Trin.)Link)、水稻(Oryza sativa L.)、野生稻(O.meyeriana subsp.granulata)、谷子(Setaria italica(L.)Beauv)、狗尾草(S.viridis (L.)Beauv)、高粱(Sorghum vulgare Pers.)和玉米(Zea mays L.)等10种禾本科植物幼苗期叶的形态结构进行比较研究。结果表明,在CO_2浓度倍增条件下,除野大麦和玉米外,其它几种禾本科植物的叶片厚度普遍增加;表皮细胞密度下降(野大麦和谷子的远轴面除外)。其中C_3种类的平均气孔密度和气孔指数下降,C_4种类则呈相反趋势。在CO_2浓度倍增条件下,栽培种类表皮细胞密度和维管束鞘细胞中的叶绿体数明显增加,野生种类则呈相反趋势。气孔密度与气孔指数基本呈正相关。     

Effect of Doubled CO2 Concentration on Leaf Chlorophyll-protein Complexes in Several Plants

The effect of doubled CO2 on the chlorophyll-protein complexes of the leaves of soybean ( Glycine max L., Ca plants), cucumber ( Cucumis sativus L., C3 plant), millet ( Setaria italica (L.) Beauv., not a very typical C4 plant) and corn (Zea mays L. ,C4 plant) was studied. Experi- mental plants were pot-cultured in polyethylene membrane (or glass) open top cultured chambers. After sowing, C02 was kept immediately either at ambient ( (350 ± 10) x 10-6) concentration for the control or at doubled CO2 ((700 ± 10) x 10-6) concentration for the treatment chambers. The chlorophyll-protein complexes of the thylakoid membrane of the plants were resolved by disk SDS- PAGE. The results showed that after doubled CO2 treatment,either in the soybean and cucmnber,or in the millet, the quantity of polymer state of PS Ⅱ light-harvesting chlorophyll a/b-protein complex (LHC Ⅱ ) had increased as the monomer state of LHC Ⅱ decreased. But such response to doubled CO2 was not found in corn, the C4 plant. The change of the state of LHC Ⅱ in soybean etc. might be an adaptive effect of plant photosynthetic mechanism to the long term elevated CO2. Thus it could increase the efficiency of the absorption, transfer and conversion of light energy in plant photosynthesis, and support the high efficiency of photosynthetic carbon assimilation.     

Resolution of 16 to 20 chlorophyll-protein complexes using a low ionic strength native green gel system

Conventional native "green gel" systems resolve at most 10 chlorophyll-protein complexes from thylakoid membranes of higher plants and green algae. Such analyses suggest a simplicity of the thylakoid membrane that is not supported by a growing body of evidence on the heterogeneity of photosystems I and II (PSI and PSII) and their associated antennae (LHCI and LHCII). We report here the development and characterization of a low ionic strength native "green gel" system that resolves from 16 to 20, mostly large chlorophyll-protein complexes from a variety of higher plant and green algal species with very little release of free pigment. In Chlamydomonas, this system resolves multiple PSI-LHCI complexes, multiple PSII-LHCII complexes, four oligomeric LHCII complexes, as well as several low electrophoretic mobility reaction center complexes, and a number of small complexes. We have obtained similar resolution with a large number of higher plant and green algal species. We also demonstrate how this system can be used as a sort of "fingerprinting" technique to distinguish thylakoids of different species, and for the analysis of photosynthetic mutants, using the chlorophyll b-less chlorina f2 mutant of barley as an example.     

Effect of Doubled-CO2 Concentration on the Ultrastructure of Chloroplasts from Medicago sativa and Setaria italica

It has been reported in quite a number of literatures that doubled CO2 concentration increased the photosynthetic rate and dry matter production of C3 plants, but substantially affected C4 plants little. However, why may CO2 enrichment promote growth and either no change or decrease reproductive allocation of the C3 species, but havinag no effects on growth characteristics of the C4 plants? So far, there has been no satisfactory explanation on that mentioned above, except the differences in their CO2 compensatory points. In the past, although some studies on ultrastructure of the chloroplasts under doubled CO2 concentration were limitedly conducted. Almost all the relevant experimental materials were only from C3 plants not from C4 plants, and even though the results were of inconsistancy. Thereby, it needs to verify whether the differences in photosynthesis of C3 and C4 plants at doubled CO2 level is caused by the difference in their chloroplast deterioration. Experiments to this subject were conducted at the Botanical Garden of Institute of Botany, Academia Sinica in 1993 and 1994. Both experimental materials from C3 plant alfalfa (Medicago sativa) and C4 plant foxtail millet (Setaria italica) were cultivated in the cylindrical open-top chambers (2.2 m in diameter × 2.4 m in height) with aluminum frames covered by polyethylene film. Natural air or air with 350× 10-6 CO2 were blown from the bottom of the chamber space with constant temperature between inside and outside of the chamber 〈0.2℃〉. Electron microscopic observation revealed that the ultrastructure of the chloroplasts from C3 plant Medicago sativa and C4 plant Seteria italica growing under the same doubled CO2 concentration were quite different from each other. The differential characteristics in ultrastructure of chloro plasts displayed mainly in the configuration of thylakoid membrances and the accumulation of starch grains. They were as follows: 1. The most striking feature was the building up of starch grains in the chloroplasts of the bundle sheath cells (BSCs) and the mesophyll cells (MCs) at doubled CO2 concentra tion. The starch grains appeared centrifugally first in the BSCs and then in the chloroplast of the other MCs. It was worthy to note that the starch grains in the chloroplasts of C4 plant Setaria ira/ica were much more than those of the C3 plant Medicago sativa . The decline of photosynthesis in the doubled CO2-grown C4 plants might be caused by an over accumulation of starch grains, that deformed the chloroplast even demaged the stroma thylakoids and grana. There might exsist a correlation between the comformation of thylakoid system and starch grain accumulation, namely conversion and transfer of starch need energy from ATP, and coupling factor (CF) for ATP formation distributed mainly on protoplastic surface (PSu) of stroma thylakoid membranes, as well as end and margin membranes of grana thylakoids. Thereby, these results could provide a conclusive evidence for the reason of non effectiveness on growth characteristics of C4 plant. 2. Under normal condition , the mature chlolroplats of higher plants usually develop complete and regularly arranged photosynthetic membrane systems . Chloroplasts from the C4 plant Setaria italica, however, exerted significant changes on stacking degree, grana width and stroma thylakoid length under doubled CO2 concentration; In these changes, the grana stacks were smaller and more numerous, and the number of thylakoids per granum was greatly increased, and the stroma thylakoid was greatly lengthened as compared to those of the control chloroplasts. But the grana were mutually intertwined by stroma thylakoid. The integrity of some of the grana were damaged due to the augmentation of the intrathylakoid space . Similarly, the stroma thylakoids were also expanded. In case. the plant was seriously effected by doubled CO2 concentration as observed in C4 plant Setaria italica , its chloroplasts contained merely the stroma (matrix) with abundant starch grains, while grana and stroma thylakoid membranes were unrecognizable, or occasionally a few residuous pieces of thylakoid membranes could be visualized, leaving a situation which appeared likely to be chloroplast deterioration. However, under the same condition the C3 plant Medicago sativa possessed normally developed chloroplasts, with intact grana and stroma thylakoid membranes. Its chloroplasts contained grana intertwined with stroma thylakoid membranes, and increased in stacking degree and granum width, in spite of more accumulated starch grains within the chloroplasts. These configuration changes of the thylakoid system were in consistant with the results of the authors another study on chloroplast function, viz. the increased capacity of chloroplasts for light absorption and efficiency of PSⅡ.     

Structural organization of photosynthetic apparatus in agranal chloroplasts of maize

We investigated the organization of photosystem II (PSII) in agranal bundle sheath thylakoids from a C(4) plant maize. Using blue native/SDS-PAGE and single particle analysis, we show for the first time that PSII in the bundle sheath (BS) chloroplasts exists in a dimeric form and forms light-harvesting complex II (LHCII).PSII supercomplexes. We also demonstrate that a similar set of photosynthetic membrane complexes exists in mesophyll and agranal BS chloroplasts, including intact LHCI.PSI supercomplexes, PSI monomers, PSII core dimers, PSII monomers devoid of CP43, LHCII trimers, LHCII monomers, ATP synthase, and cytochrome b(6)f complex. Fluorescence functional measurements clearly indicate that BS chloroplasts contain PSII complexes that are capable of performing charge separation and are efficiently sensitized by the associated LHCII. We identified a fraction of LHCII present within BS thylakoids that is weakly energetically coupled to the PSII reaction center; however, the majority of BS LHCII is shown to be tightly connected to PSII. Overall, we demonstrate that organization of the photosynthetic apparatus in BS agranal chloroplasts of a model C(4) plant is clearly distinct from that of the stroma lamellae of the C(3) plants. In particular, supramolecular organization of the dimeric LHCII.PSII in the BS thylakoids strongly suggests that PSII in the BS agranal membranes may donate electrons to PSI. We propose that the residual PSII activity may supply electrons to poise cyclic electron flow around PSI and prevent PSI overoxidation, which is essential for the CO(2) fixation in BS cells, and hence, may optimize ATP production within this compartment.     

Correlation of iron content, spectral forms of chlorophyll and chlorophyll-proteins in iron deficient cucumber (Cucumis sativus)

Leaves and chloroplast suspensions of severely and slightly iron deficient cucumber ( Cucumis sativus L.) plants were characterized by low-temperature fluorescence emission spectroscopy and Deriphat polyacrylamide gel electrophoresis. The emission spectra of the chloroplast suspensions were resolved into Gaussian components and those changes induced by iron deficiency were related to the variations in the chlorophyll-protein pattern. The symptoms described with these methods were also correlated with the iron content of the leaves. It was concluded that the lack of physiologically active iron caused a relative decrease of photosystem I (PSI) and light harvesting complex I (LHCI), together with the long wavelength fluorescence, especially the 740 nm Gaussian component, and. to a much lesser extent, of the photosystem II (PSII) core complexes (relative increase of 685, 695 nm components). However, the relative decrease in the amount of light harvesting complex II (LHCII) was followed by a relative increase in its fluorescence band at 680 nm, showing that energy transfer from LHCII to core complex II (CCII) was partly disturbed. Thus iron deficiency affected the photosynthetic apparatus in a complex way: it decreased the synthesis of chlorophylls (Chls) and influenced the expression and assembly of Chl-binding proteins.     

Species-dependence of the pattern of plant photosynthetic rate response to light intensity transition from saturating to limiting one]

By observing the photosynthetic responses of leaves to changes in light intensity and CO(2) concentration it was found that among the more than 50 plant species examined 32 species and 25 species showed respectively the V pattern and L pattern of the photosynthetic response to light intensity transition from saturating to limiting one (Figs.1 and 2 and Table 1). The pattern of photosynthetic response to light intensity transition is species-dependent but not leaf developmental stage-dependent (Fig.3). The species-dependence was not related to classification in taxonomy because the photosynthetic response might display the two different patterns (V and L) in plants of the same family, for example, rice and wheat (Gramineae), soybean and peanut (Leguminosae). It seemed to be related to the pathway of photosynthetic carbon assimilation because all of the C(4) plants examined (maize, green bristlegrass and thorny amaranth) displayed the L pattern. It might be related to light environment where the plants originated. The V pattern of photosynthetic response to light intensity transition was often observed in some plants grown in shade habitats, for example, sweet viburnum and Japan fatsia, while the L pattern was frequently observed in those plants grown in sunny habitats, for example, ginkgo and cotton. Furthermore, the ratio of electron transport rate to carboxylation rate in vivo measured at limiting light was far higher in the V pattern plants (mostly higher than 10) than in the L pattern plants (mostly lower than 5), but the ratio measured at saturating light had no significant difference between the two kinds of plants (Table 2). These results can be explained in part by that the V pattern plant species have larger light-harvesting complex (LHCII) and at saturating light the reversible dissociation of some LHCIIs from PSII reaction center complex occurs. The pattern of photosynthetic response to light intensity transition and the ratio of electron transport rate to carboxylation rate in vivo measured at limiting light can probably be used as a criterion to distinguish sun plants from shade plants. In the observation of photosynthetic response to light intensity transition the use of saturating light is very important because using non-saturating light can form an artifact, which leads to incorrect conclusion (Fig.4).     

Differential changes in degradation of chlorophyll-protein complexes of photosystem I and photosystem II during flag leaf senescence of rice.

The stability of chlorophyll-protein complexes of photosystem I (PSI) and photosystem II (PSII) was investigated by chlorophyll (Chl) fluorescence spectroscopy, absorption spectra and native green gel separation system during flag leaf senescence of two rice varieties (IIyou 129 and Shanyou 63) grown under outdoor conditions. During leaf senescence, photosynthetic CO(2) assimilation rate, carboxylase activity of Rubisco, chlorophyll and carotenoids contents, and the chlorophyll a/b ratio decreased significantly. The 77 K Chl fluorescence emission spectra of thylakoid membranes from mature leaves had two peaks at around 685 and 735 nm emitting mainly from PSII and PSI, respectively. The total Chl fluorescence yields of PSI and PSII decreased significantly with senescence progressing. However, the decrease in the Chl fluorescence yield of PSI was greater than in the yield of PSII, suggesting that the rate of degradation in chlorophyll-protein complexes of PSI was greater than in chlorophyll-protein complexes of PSII. The fluorescence yields for all chlorophyll-protein complexes decreased significantly with leaf senescence in two rice varieties but the extents of their decrease were significantly different. The greatest decrease in the Chl fluorescence yield was in PSI core, followed by LHCI, CP47, CP43, and LHCII. These results indicate that the rate of degradation for each chlorophyll-protein complex was different and the order for the stability of chlorophyll-protein complexes during leaf senescence was: LHCII>CP43>CP47>LHCI>PSI core, which was partly supported by the green gel electrophoresis of the chlorophyll-protein complexes.     

大气CO2浓度倍增对植物暗呼吸的影响

以长期生长于350和700μmolCO_2·mol~(-1)空气的开顶式培养室的杜仲(Eucommia ulmoides Oliv.)、紫花苜蓿(Medicago sativa L.)、玉米(Zea mays L.)等10种植物的离体成熟叶片或整株为材料,研究不同测定温度(15～35℃)下,CO_2浓度倍增对植物暗呼吸的影响。结果表明:在较低温度(15℃、20℃)下,CO_2浓度倍增对植物暗呼吸没有显著效应,在较高温度(30℃、35℃)下多数被测植物的暗呼吸显著增强。讨论了实验所得结果在未来全球气候变化中的可能的意义。     

Appearance of type 1, 2, and 3 light-harvesting complex II and light-harvesting complex I proteins during light-induced greening of barley (Hordeum vulgare) etioplasts.

Monospecific antibodies directed against typical domains of type 1, 2, and 3 light-harvesting complex (LHC) II apoproteins have been used (a) to identify these apoproteins on denaturing sodium dodecyl sulfate gels of barley (Hordeum vulgare) thylakoids, (b) to determine their distribution between grana and stroma membranes, and (c) to follow their accumulation during light-induced greening of etioplasts. In addition, we have studied the light-induced assembly of chlorophyll-protein complexes with a native green gel system (K.D. Allen, L.A. Staehelin [1991] Anal Biochem 194: 214-222). Western blot analysis of the three major LHCII apoprotein bands has identified the highest molecular mass band at 27.5 kD as containing the type 2 LHCII apoproteins, the middle band at 26.9 kD as containing the type 1 LHCII apoproteins, and the lowest band at 26.0 kD as containing the type 3 LHCII apoproteins. During light-induced greening of 6-d-old etiolated barley seedlings, the type 1, 2, and 3 LHCII apoproteins accumulate simultaneously and at similar rates but appear somewhat sooner (< 4 h) in thylakoids from apical than from basal (4-8 h) leaf segments. LHCI polypeptides accrue with similar kinetics, whereas the 33-kD oxygen-evolving complex polypeptides can be detected already in the 0-h light samples. During the most rapid phase of thylakoid development (8-24 h), two slightly larger (28.3 and 28.7 kD) type 2 LHCII apoproteins (precursor intermediates?) also accumulate in the thylakoids. No corresponding higher molecular mass forms of type 1 and 3 LHCII apoproteins could be detected. It is interesting that differences are still apparent in the composition of chlorophyll-protein complexes of light-control plants and those of etiolated plants greened for 8 d.     

Nod factor [Nod Bj V (C(18:1), MeFuc)] and lumichrome enhance photosynthesis and growth of corn and soybean

The foliar application of Nod factor [Nod Bj V (C(18:1), MeFuc)] enhanced (P<0.05) the photosynthetic rate of corn; the increases were 36%, 23% and 12% for 10(-6), 10(-8) and 10(-10)M treated plants, respectively. Similarly, lumichrome at 10(-5) and 10(-6)M stimulated the photosynthetic rate of corn plants 1 and 2 days after application. Lumichrome (10(-5) and 10(-6)M) also increased the photosynthetic rates of soybean plants 3 days after treatment. Foliar applications of LCO (10(-6)M) to corn and soybean and of lumichrome (10(-5)M) to soybean increased leaf area, shoot dry mass and total dry mass relative to control plants. However, lumichrome treatments did not affect any growth variable of corn. Results of this study indicate that this signal compound can enhance the photosynthetic rate and growth of plants.