不同土壤水分条件下紫藤叶片生理参数的光响应

测定了不同土壤湿度下2年生紫藤叶片光合速率（P_n）、蒸腾速率（T_r）及水分利用效率（WUE）等生理参数的光响应过程,探讨了紫藤正常生长发育所需的土壤水分和光照条件.结果表明:紫藤叶片的P_n、T_r及WUE对土壤湿度和光照强度的变化具有明显的阈值响应.维持紫藤正常生长（同时具有较高P_n和WUE）的土壤湿度范围为:体积含水量（W_v）15.3%～26.5%、相对含水量（W_r）46.4%～80.3%,最佳土壤湿度约为W_v 23.3%、W_r 70.6%.紫藤叶片对光照环境的适应性较强,在光合有效辐射强度（PAR）为600～1 600 μmol·m^-2·s^-1时,P_n和WUE具有较高水平,饱和光强在PAR为800～1 000 μmol·m^-2·s^-1.紫藤叶片光合作用非气孔限制的发生与土壤湿度与光照强度密切相关,W_v为18.4%～26.5%、W_r为55.8%～80.3%时,光合作用主要受气孔限制,光照强度的影响较小;超出此范围后,其受光照强度的影响较大,出现由气孔限制转变为非气孔限制的PAR临界值.紫藤正常生长允许的最低土壤湿度约为W_v 11.9%、W_r 36.1%,允许最高PAR约为1 000 μmol·m^-2·s^-1,是紫藤叶片光合机构受到破坏的临界点.     

热带季节雨林冠层树种绒毛番龙眼的光合生理生态特性

采用Li-6400便携式光合作用测定仪,对西双版纳热带季节雨林冠层树种绒毛番龙眼成树树冠上、中、下3层叶片进行了测定,分析西双版纳热带季节雨林冠层树木的光合作用.结果表明,绒毛番龙眼成树具有喜光的光合特性,光饱和点较高(1 000～1 500 μmol·m^-2·s^-1),而光补偿点较低(7.7～15.3 μmol·m^-2·s^-1),对光环境有较强的适应和调节能力,光合有效辐射是影响绒毛番龙眼光合日进程的关键因子;12月,叶片处于成熟期,生长良好,光合能力较强,树冠上层净光合速率（P_n）日变化为单峰型,最大净光合速率（A_max）约为8.9 μmol CO₂·m^-2·s^-1;4月处于新老树叶更替期,光合能力下降,树冠上层P_n日变化为双峰型,中午出现“午休”现象,树冠上层A_max约为4.3 μmol CO₂·m^-2·s^-1;7月上、中层叶片P_n为单峰型,下层出现“午休”.如人为使CO₂浓度在短期内迅速升高,则绒毛番龙眼的P_n会增加,而气孔导度和蒸腾速率降低;CO₂浓度从400 μmol·mol^-1升高到800 μmol·mol^-1时,干季水分利用效率（WUE）提高约50%～100％,雨季WUE较低.     

检疫性杂草毒莴苣的光合特征及其入侵地群落学生态调查

毒莴苣是我国东南沿海地区的新入侵杂草,也是国家进境植物的检疫对象.调查发现,毒莴苣植株高大,易在入侵地形成群落优势种;常见的伴生杂草有小飞蓬、野塘蒿、鬼针草、裂叶月见草、裂叶牵牛、狗尾草、野胡萝卜、苍耳、一年蓬、山莴苣、葎草、龙葵和钻形紫菀等.应用LCA 4光合蒸腾测定系统对毒莴苣进行净光合速率测定,结果表明：该种实测净光合速率高达21.22±0.45 μmol CO₂·m^-2·s^-1,比入侵性杂草一年蓬、野塘蒿稍低,比藜、北美车前、山莴苣等高,是一种高光效植物;根据毒莴苣的光合-响应曲线,该外来入侵种的理论光补偿点为37.58 μmol·m^-2·s^-1, 光饱和点为1 480 μmol·m^-2·s^-1,理论最大净光合速率20.81 μmol CO₂·m^-2·s^-1;毒莴苣的光合作用具有午休现象,是由于高光照和高温导致气孔阻力增加、气孔关闭,影响了植株对外的气体交换;影响净光合速率的主要因素是气孔导度、叶面光合有效辐射和叶片的蒸腾.     

豚草叶片和果实气体交换特性与11种土壤重金属相关性

对10个样地中Cu、Pb、Zn、Mn、Cr、Co、Ni、Cd、As、Sb和 Hg 11种土壤重金属含量及样地内豚草叶片和果实气体交换特性进行测定.结果表明,样地内豚草叶片的净光合速率在1.88～9.41 μmol·m^-2·s^-1,而果实的净光合速率最高可达2.81 μmol·m^-2·s^-1.叶片的呼吸速率、气孔导度、光合速率和水分利用效率的平均值分别为1.81 μmol·m^-2·s^-1、75.7 mmol·m^-2·s^-1、6.05 μmol·m^-2·s^-1和4.72 μmol·mmol^-1,分别是果实的5.26、0.64、1.31和1.69倍,说明非同化器官幼嫩果实具有与叶片相当,甚至更强的呼吸、光合能力和水分利用效率;研究地点重金属Ni达到轻微污染水平,其它重金属含量都接近或者显著低于重金属污染的阈值.相关分析和多元回归分析显示,大部分土壤重金属（如Cu、Pb、Zn、Cd、As、Sb和Hg）含量的高低对豚草气体交换特性没有显著影响,仅部分重金属含量与豚草的叶片、果实气体交换特性密切相关,如Ni和Cr对豚草叶片、果实的气孔导度及水分利用效率显著相关;Cr与豚草叶片饱和光合速率显著相关;而As与豚草果实的气孔导度显著相关.表明大部分土壤重金属对叶片和球果的气体交换没有直接影响,而Ni、Cr和As可以在轻微污染甚至没有达到污染水平时影响豚草的气体交换特性.     

钾素水平对网纹甜瓜叶片光合特性及叶绿体亚显微结构的影响

在设施基质栽培条件下,研究了营养液中120、240及360 mg·L^-1 3个钾素水平对网纹甜瓜‘甜甜1号’叶片光合特性及叶绿体亚显微结构的影响.结果表明,营养液中钾素水平过低（120 mg·L^-1）或过高（360 mg·L^-1）均导致网纹甜瓜叶片净光合速率下降,使叶绿体片层结构混乱、变形和片层数减少,但对CO₂补偿点（70 μl·L^-1）、饱和CO₂（600 μl·L^-1）、光补偿点（50 μmol·m^-2·s^-1）无显著影响.适宜的钾素水平能显著提高叶片的饱和光强、羧化效率和表观量子效率,3个指标分别为1 200 μmol·m^-2·s^-1、0.1364和0.0237.在试验条件下,提高温室内基质栽培网纹甜瓜叶片光合效率的最适钾素水平为240 mg·L^-1.     

镇江内江湿地不同演替阶段植物群落小气候日动态

2005年5月,选择镇江内江湿地具有代表性的裸地、虉草群落和芦苇群落,分别代表植被群落的不同演替阶段,测定不同群落、不同层次的光照强度、气温、土温和空气相对湿度,研究其植物群落小气候的日动态.结果表明,随演替由裸地到虉草群落到芦苇群落进行,群落内光照强度、气温和土壤温度均明显降低,日变幅减小.其中,日均光照强度由1 204.7 μmol·m^-2·s^-1降至141.28 μmol·m^-2·s^-1,日均变幅由1 126μmol·m^-2·s^-1降至265 μmol·m^-2·s^-1;日均气温由32.2 ℃降至24.9 ℃,日均变幅由12.75 ℃降至4.8 ℃;日均土温由21.83 ℃降至19.47 ℃,日均变幅由4.5 ℃降至2.1 ℃.群落内空气相对湿度明显升高(由58.95%增至87.3%）,变幅减小(由29.75%降至5.15%）.生境具有早期的开放性和后期的封闭性,小气候环境朝着更为阴、凉、湿的环境变化,且波动性减弱,稳定性增强.各群落内的光强、气温、湿度及土温之间均存在一定相关,但不同演替阶段各因子间相关程度各异.     

嫁接对低温弱光下甜椒幼苗光合作用的影响

以‘卫士’和‘部野丁’为砧木,以‘赤峰特选’为接穂进行嫁接,在光照培养箱内对甜椒自根苗和嫁接苗进行低温(8 ℃/ 5℃)弱光(100 μmol·m^-2·s^-1)处理,处理7 d后在正常条件（25 ℃/18 ℃,PFD 550～600 μmol·m^-2·s^-1）下恢复3 d,研究低温弱光下甜椒嫁接苗和自根苗气体交换参数、羧化效率和荧光参数等的变化.结果表明：低温弱光胁迫3 d时,甜椒幼苗叶片的光合速率（P_n）、气孔导度（G_s）和羧化效率（CE）均下降50%以上,之后P_n、G_s趋于平稳,CE持续下降;胞间CO₂浓度（C_i）呈先下降后上升趋势.低温弱光下,甜椒幼苗的暗下最大光化学效率(F_v/F_m)、光下实际光化学效率（Ф_PSⅡ）及电子传递速率（ETR）显著降低,初始荧光(F_o)有所升高,表明其光合机构受到一定伤害,但处理结束3 d后基本恢复.与自根苗相比,嫁接苗在各处理阶段的P_n、G_s、CE、Ф_PSⅡ、F_v/F_m和ETR都有不同程度的提高,F_o明显降低.可见,嫁接可显著提高甜椒幼苗的光合功能,减轻低温弱光对其光合作用的影响.     

武夷山不同海拔植被土壤呼吸季节变化及对温度的敏感性

以武夷山国家级自然保护区为实验基地,研究了4种不同海拔高度上植物群落土壤呼吸速率的季节变化及其对温度的敏感性,以及与主要环境因子的关系.结果表明：4种不同海拔植物群落的土壤呼吸速率均具有明显且一致的季节变化,其中夏季土壤呼吸速率最大,为3.10～6.57 μmol CO₂·m^-2·s^-1,冬季最小,为0.27～1.15 μmol CO₂·m^-2·s^-1;土壤呼吸速率与土壤温度呈显著指数相关,不同样地土壤呼吸速率与土壤含水率和凋落物输入量的关系各不相同;高海拔地区土壤呼吸的Q₁₀值显著高于低海拔地区.在中亚热带地区,不同海拔土壤呼吸速率的季节波动主要受土壤温度的影响;在未来全球气候变暖的背景下,高海拔地区的土壤可能释放更多的CO₂.     

几种主要环境因子对布朗葡萄藻(Botryococcus braunii)光合作用的影响

利用测定净光合放氧速率的方法研究了光照强度、温度、pH值、盐度对布朗葡萄藻Botryococcus braunii UTEX 572和B.braunii UTEX 2441两个品系的光合作用的影响。B.braunii UTEX 572的适宜光照强度范围400～1600μmol·m^-2·s^-1,光饱和点在800μmol·m^-2·s^-1附近;适宜温度范围25～35℃,最适温度30℃;适宜pH范围5.0～8.0,最适pH7.0;适宜盐度范围0～0.2mol/L,最适盐度0.1mol/L。B.braunii UTEX 2441的适宜光照强度范围400～1600μmol·m^-2·s^-1,光饱和点在400μmol·m^-2·s^-1附近;适宜温度范围25～35℃,最适温度30℃;适宜pH范围5.0～8.0,最适pH7.0;对盐度的适应范围较小,盐度升高,光合放氧速率明显下降。两个布朗葡萄藻净光合放氧速率随光照强度、温度、pH值和盐度变化的规律,表明布朗葡萄藻的基本生理生态学特征:适应于较强的光照强度、较高的温度、中性偏酸的环境和较低的盐度。对布朗葡萄藻基本生理生态学特征的了解,为培养条件的优化提供了依据。2个布朗葡萄藻品系对光强、温度、pH值和盐度变化的反应有所不同:与B.braunii UTEX 2441相比,B.braunii UTEX 572具有更高的光饱和点,适应更高的温度,对pH值变化有更宽的适应范围,适当提高盐度对其光合作用有促进作用,表明B.braunii UTEX 572在快速生长繁殖方面具有更大的潜力,这一研究结果为筛选适合于大量培养的优良藻种提供了依据。     

阔叶红松林林冠空隙光强异质性对红松幼树生长的影响

利用Li-6400光合测定系统,研究了长白山阔叶红松林4个不同尺度林窗内光照强度的异质性,分析红松幼树在林窗内9个方位的光合作用日变化特征.结果表明：林窗内9个方位出现光合有效辐射(PAR)峰值顺序为:西实际林窗、北扩展林窗、林窗中心＞南实际林窗、南扩展林窗、东扩展林窗、东实际林窗＞西扩展林窗、北实际林窗,光照呈东-西、南-北不对称分布,光照梯度在西、北方向变化较大,但各方向距中心不同距离的日均PAR无显著差异.林窗Ⅰ～Ⅳ日均PAR分别为21.85、45.57、66.02和23.48 μmol·m^-2·s^-1,相互之间均达显著差异水平（P＜0.05）.PAR与净光合速率(P_n)呈显著正相关,且相关系数随PAR增大而增大.随林窗面积的增大,PAR和P_n均先增大后减小; 当林窗面积为267 m²时,二者同时达到最大值.     

Influence of light on adventitious root formation in birch shoot culturesin vitro

The influence of light of different spectral composition and levels of irradiance (2-40 Wm-²) on adventitious root formation (ARF) in birch shoot segments was investigated. Spontaneous rooting of shoot segments occurred in segments with intact apical or axillary meristems. Concerning ARF shoot meristems could be substituted by application of auxin. The very low rooting percentage of shoot segments in darkness was improved considerably by auxin application. Irradiation of cuttings was a requirement for a high percentage of spontaneous rooting. The promoting effect of light was dependent on its spectral composition and was the highest under red followed by white and blue light. The low rooting response under blue light was enhanced almost to the red light level by shielding the root-forming cutting base from light.     

Enhancement of photosynthetic O2 evolution in Chlorella vulgaris under high light and increased CO2 concentration as a sign of acclimation to phosphate deficiency.

The photosynthetic oxygen evolution of Chlorella vulgaris (Beijer.) cells taken from phosphate-deficient (-P) and control cultures was measured during 8 days of culture growth. Under inorganic carbon concentration (50 microM) in the measuring cell suspension and irradiance (150 micromol m(-2) s(-1)), the same as during culture growth, there were no marked differences in the photosynthetic O2 evolution rate between the -P cells and the controls. The much slower growth of -P cultures indicated that the utilization of absorbed photosynthetically active radiation (PAR) in the CO2 assimilation and biomass production were in -P cells less efficient than in the controls. Alga cells under the phosphorus stress utilized more of the absorbed PAR in the nitrate reduction than the control cells. However, under conditions of more efficient CO2 supply (inorganic carbon concentration 150 microM, introducing of exogenous carbonic anhydrase to the measuring cell suspension) and under increased irradiance (500 micromol m(-2) s(-1)), the photosynthetic O2 evolution in -P cells reached a higher rate than in the controls. The results suggest that in -P cells the restricted CO2 availability limits the total photosynthetic process. But under conditions more favorable for the CO2 uptake and under high irradiance, the -P cells may reveal a higher photosynthetic oxygen evolution rate than the controls. It is concluded that an increased potential activity of the photosynthetic light energy absorption and conversion in the C. vulgaris cells from -P cultures is a sign of acclimation to phosphorus stress by a sun-type like adaptation response of the photosynthetic apparatus.     

外源甜菜碱对水分胁迫下桃树生理响应的影响

以4年生盆栽“庆丰”桃树为试材,研究了水分胁迫下桃树叶片中甜菜碱含量的变化规律及叶面喷施甜菜碱对水分胁迫下桃树生理响应的影响.结果表明：正常供水情况下,桃树叶片中甜菜碱含量为75.9～80.5 μg·g^-1FM , 随着水分胁迫程度的加深,甜菜碱含量逐渐增加,停水第16 天时达278.9 μg·g^-1FM ;正常供水时桃叶片细胞质膜透性为8.06%～8.61%,水分胁迫下增至28.62%,叶面喷施100和500 mg·L^-1甜菜碱16d后分别为26.25%和21.79%;过氧化氢(H₂O₂)含量由正常情况下的27.2～32.5 μmol·g^-1FM 增至胁迫后的76.4 μmol·g^-1FM,叶面喷施100和500 mg·L^-1甜菜碱后分别为73.2和68.5 μmol·g^-1 FM;水分胁迫下,抗坏血酸过氧化物酶(AsA-POD)活性峰值为0.435 mg·g^-1 FM,甜菜碱处理后峰值达到0.490 mg·g^-1 FM;游离脯氨酸与可溶性糖在干旱胁迫下逐渐累积, 500 mg·L^-1甜菜碱处理分别为2.878 mg·g^-1 FM和37.6 mg·g^-1 FM,均低于单纯胁迫及100 mg·L^-1甜菜碱处理;可溶性蛋白质含量在水分胁迫下呈下降趋势,甜菜碱处理后最小值为4.03 mg·g^-1 FM,较单纯胁迫下的最低值（3.14 mg·g^-1 FM）高20.3%.表明叶面喷施甜菜碱能在一定程度上减轻桃树的受害程度,提高其抗旱性.     

Leaf respiration of snow gum in the light and dark. Interactions between temperature and irradiance

We investigated the effect of temperature and irradiance on leaf respiration (R, non-photorespiratory mitochondrial CO(2) release) of snow gum (Eucalyptus pauciflora Sieb. ex Spreng). Seedlings were hydroponically grown under constant 20 degrees C, controlled-environment conditions. Measurements of R (using the Laisk method) and photosynthesis (at 37 Pa CO(2)) were made at several irradiances (0-2,000 micromol photons m(-2) s(-1)) and temperatures (6 degrees C-30 degrees C). At 15 degrees C to 30 degrees C, substantial inhibition of R occurred at 12 micromol photons m(-2) s(-1), with maximum inhibition occurring at 100 to 200 micromol photons m(-2) s(-1). Higher irradiance had little additional effect on R at these moderate temperatures. The irradiance necessary to maximally inhibit R at 6 degrees C to 10 degrees C was lower than that at 15 degrees C to 30 degrees C. Moreover, although R was inhibited by low irradiance at 6 degrees C to 10 degrees C, it recovered with progressive increases in irradiance. The temperature sensitivity of R was greater in darkness than under bright light. At 30 degrees C and high irradiance, light-inhibited rates of R represented 2% of gross CO(2) uptake (v(c)), whereas photorespiratory CO(2) release was approximately 20% of v(c). If light had not inhibited leaf respiration at 30 degrees C and high irradiance, R would have represented 11% of v(c). Variations in light inhibition of R can therefore have a substantial impact on the proportion of photosynthesis that is respired. We conclude that the rate of R in the light is highly variable, being dependent on irradiance and temperature.     

The role of light and polar auxin transport in root regeneration from hypocotyls of tomato seedling cuttings

A relationship between light conditions, auxin transport and adventitious root formation by hypocotyls of tomato seedling cuttings was demonstrated. Effective rooting of tomato seedling cuttings was observed under continuous white light (WL) irradiation. However, root formation was reduced in darkness or under red (RL) or blue light (BL). At least 3/4-day-long irradiation treatment with (WL) was necessary to increase the number of roots formed in comparison with control cuttings grown in darkness. Light was most effective if applied during the first half of the 13-day-long rooting period. The role of photoreceptor-dependent light perception in the light-regulation of rooting was tested using tomato photomorphogenic mutants: aurea (au) and high pigment (hp). When exposed to WL both mutants generated fewer roots then their isogenic wild type (WT). In darkness or under BL and RL less roots were formed on all plants and no difference was observed between mutants and WT plants. TIBA (2,3,5-triiodobenzoic acid) inhibited rooting in a dose-dependent manner both in darkness and under WL. However, although rooting was suppressed by 0.75 M TIBA in the dark, 8 M TIBA was necessary to block root formation in continuous WL. Inhibition of rooting by TIBA was most efficient when applied at the initial period of rooting, a 1-day-long treatment with TIBA being sufficient to suppress rooting if given during the first 2 days of culture. Later treatment had much less effect on the root formation.     

Reduced irradiance and applied auxin influence carbohydrate relations in Pinus banksiana cuttings during propagation

Untreated and indole-3-butyrie acid-treated (IBA) cuttings from 90-day-old Pinus banksiana Lamb, stock plants were propagated under normal greenhouse irradiance (max. 900 $$mol m^-2 s^-1) and shade (max. 120 $$mol m^-2 s^-1) to determine effects on adventitious rooting and on reducing sugar and starch concentrations in needles and basal stems. In one experiment, cuttings were assessed at days 15 and 25 of propagation for basal 1-cm stem fresh weight, proportion rooted, number of roots and longest root length. In a second experiment with cuttings, basal 1-cm stem fresh weight and concentrations of reducing sugar and starch in needles and basal stems were measured each day for the first 10 days of propagation. Carbohydrate measurements were also made for seedling stock plants as controls for the second experiment. Carbohydrate data for cuttings were primarily evaluated based on net (cutting minus seedling) concentrations, to correct for changes in cuttings not related to adventitious rooting. Increase of basal stem fresh weight and rooting of cuttings, based on all measured variables, occurred in the order: light + IBA > light > shade + IBA > shade. The best rooting required the greater irradiance. Compared to results from cuttings in the light, shading resulted in lesser accumulations of reducing sugars and starch in needles and basal stems. Reducing sugar: starch concentration ratios were significantly greater in shade- vs light-propagated cuttings, IBA treatment did not offset the effects of shade on rooting or on reducing sugar and starch concentrations or ratios. Overall, the results suggested that decreased reducing sugar and starch concentrations and/or their increased ratios are associated with shade-induced poor rooting of P. banksiana cuttings.     

脱落酸对低温下雷公藤幼苗光合作用及叶绿素荧光的影响

以1年生雷公藤扦插苗为试材,研究低温胁迫下不同浓度外源脱落酸（ABA,0、5、10、15、20、25 mg·L^-1)叶面喷施处理对雷公藤叶片光合作用及叶绿素荧光参数的影响.结果表明：喷施20 mg·L^-1的ABA能显著提高雷公藤幼苗的抗冷性,减缓低温下雷公藤叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(g_s)、胞间CO₂浓度(C_i)的下降幅度,提高幼苗叶片的光合能力.低温处理6 d后,随着ABA浓度上升,雷公藤叶片的初始荧光(F_o)下降,最大荧光(F_m)和PSII最大光化学效率(F_v/F_m)上升,PSII实际光化学量子产量(Φ_PSⅡ)、光化学猝灭系数(q_P)先下降后上升,而非光化学猝灭系数(q_N)呈下降－上升－下降趋势.P_n、g_s、q_P、F_m和F_v/F_m均在20 mg·L^-1ABA处理时达到峰值.不同浓度ABA的相对电子传递速率(rETR)随着光化光强度增加呈先上升后下降的趋势,当光化光强度(PAR)达到395 μmol·m^-2s^-1时,各处理的rETR达到最高值,其中25 mg·L^-1和20 mg·L^-1ABA处理分别比对照高17.1%和5.2%.雷公藤叶片Φ_PSⅡ的光响应曲线均随光化光强度升高而下降,q_N的光响应曲线则呈相反趋势.     

Water stress and root formation in pea cuttings

The stock plants of pea (Pistum sativium L. cv. Alaska) grown for 11 days at 16 W m^?2 38 W m^?2 were subjected to different degrees of moisture stress, simulated with polyethyleneglycol (PEG, 6000) for different periods. The cuttings were made at the end of stress treatments, planted in perlite and allowed to root in a mist propagation chamber. The number of adventitious roots formed on the cuttings from non-stressed plants was significantly higher under low (16 W m^?2) than under high (38 W ^m?2) irradiance. However, under the influence of short duration stress the number of roots increased significantly under high but not under low irradiance. There was significantly poor rooting after prolonged stress under both irradiances. The leaf osmotic potential ψ_π showed a greater reduction with increasing degree and duration of stress at 38 W m^?2 than at 16 W m^?2. The differential rooting behaviour as a result of stress levels and irradiances is discussed in the light of available literature on adventitious root formation.     

Chromatic photoacclimation, photosynthetic electron transport and oxygen evolution in the chlorophyll d-containing oxyphotobacterium Acaryochloris marina

Changes in photosynthetic pigment ratios showed that the Chlorophyll d-dominated oxyphotobacterium Acaryochloris marina was able to photoacclimate to different light regimes. Chl d per cell were higher in cultures grown under low irradiance and red or green light compared to those found when grown under high white light, but phycocyanin/Chl d and carotenoid/Chl d indices under the corresponding conditions were lower. Chl a, considered an accessory pigment in this organism, decreased respective to Chl d in low irradiance and low intensity non-white light sources. Blue diode PAM (Pulse Amplitude Modulation) fluorometry was able to be used to measure photosynthesis in Acaryochloris. Light response curves for Acaryochloris were created using both PAM and O(2) electrode. A linear relationship was found between electron transport rate (ETR), measured using a PAM fluorometer, and oxygen evolution (net and gross photosynthesis). Gross photosynthesis and ETR were directly proportional to one another. The optimum light for white light (quartz halogen) was about 206+/-51 micromol m(-2) s(-1) (PAR) (Photosynthetically Active Radiation), whereas for red light (red diodes) the optimum light was lower (109+/-27 micromol m(-2) s(-1) (PAR)). The maximum mean gross photosynthetic rate of Acaryochloris was 73+/-7 micromol mg Chl d(-1) h(-1). The gross photosynthesis/respiration ratio (P(g)/R) of Acaryochloris under optimum conditions was about 4.02+/-1.69. The implications of our findings will be discussed in relation to how photosynthesis is regulated in Acaryochloris.