不同透光率和土壤含水量对夏蜡梅枝条生长量及叶片部分生理指标的影响

采用盆栽实验方法,研究了不同透光率(100%、50%、25%和15%)和土壤含水量(10%、25%、45%和65%)对夏蜡梅(Sinocalycanthus chinensis Cheng et S. Y. Chang)枝条生长量和叶片部分生理指标的影响,并对枝条生长量和叶片各生理指标间的相关性进行了分析.结果表明:在土壤含水量10%或全光照(透光率100%)条件下,夏蜡梅枝条生长量和叶片的叶绿素含量最低,MDA和可溶性糖含量以及SOD和POD活性均较高,脯氨酸和可溶性蛋白质含量最高;在透光率50%和25%或土壤含水量 25%和45%的条件下,枝条生长量和叶片的叶绿素含量提高,其他各项生理指标则有所降低;在透光率15%或土壤含水量65%的条件下,枝条的生长量和叶片叶绿素含量略有减小,其他各项生理指标则有所提高.总体上,随透光率的提高和土壤含水量的减小,夏蜡梅枝条生长量和叶片叶绿素含量呈逐渐减小的趋势,其他各项生理指标呈逐渐提高的趋势.透光率和土壤含水量对夏蜡梅枝条生长量及叶片的生理指标有交互作用,遮阳可在一定程度上缓解土壤干旱胁迫对夏蜡梅的伤害,增加土壤含水量也可在一定程度上缓解强光照对夏蜡梅的伤害;但透光率过低(15%)或土壤含水量过高(65%)则不利于夏蜡梅的生长.相关性分析结果表明,枝条生长量与叶片POD活性、脯氨酸和MDA含量呈极显著的负相关(P＜0.01),说明在胁迫条件下叶片这3项指标的变化与夏蜡梅枝条生长紧密相关,可通过这些指标判定夏蜡梅对其生境的适应程度.根据实验结果推测,在夏季高温阶段,夏蜡梅适宜在透光率50%、土壤含水量45%的生境中生长,在上海地区种植夏蜡梅应适当配植乔木和地被植物.     

光照强度对水鬼蕉(Hymenocallis littoralis)生长及生理生态特性的影响

研究了4个光照强度水平对水鬼蕉(Hymenocallis littoralis (Jacq.) Salisb.)在土壤和碎石基质人工湿地中生长的影响.4个光处理平均光照强度(μmol m-2 s-1)是:701(全光照,光强I)、495(全光照的71.4%,光强Ⅱ)、304(全光照的44.7%,光强Ⅲ)、141(全光照的20.2%,光强Ⅳ).研究表明,在较弱光强(III、IV)下,水鬼蕉的株高、叶生物量、叶片长度、叶绿素含量通常显著高于较高光强(I、II)下的植物.较低光强植株的生物量通常高于较高光强的植株,但差异一般不显著.光合作用和根生物量虽以全光照的植株较高,但不同光强之间差异不显著.可见,水鬼蕉具有一定的耐阴性,适度的荫蔽(全光照的约50%)有利于其生长.水鬼蕉在土壤和碎石基质对光照强度的反应不完全相同.在相同的光照强度下,生长于碎石基质的水鬼蕉的测定指标(除叶绿素含量外)通常都显著高于生长于土壤基质的植物.水鬼蕉100 cm左右的高度、较慢的生长速度、在碎石基质适度遮荫有利于生长等特点使其适合用于构建多种植物人工湿地群落的中下层植物,是一种在污水处理人工湿地有较好应用潜力的植物.     

夏蜡梅及其主要伴生种叶的灰分含量和热值

分别于2006年7月、10月和2007年4月,对全光照、林缘和林下3种光环境下夏蜡梅及群落中35种主要植物叶的灰分含量和去灰分热值进行测定,分析它们在光合作用中对太阳能的固定和积累能力。不同光环境下夏蜡梅叶灰分含量的大小顺序都是全光照＞林缘＞林下,10月3种光环境下夏蜡梅叶灰分含量均高于4月和7月,均差异显著。4月、7月和10月,林下和全光照环境下的叶去灰分热值呈先下降后上升的趋势,而林缘中叶去灰分热值却逐渐下降。群落各层植物的灰分含量大小顺序为草本层＞灌木层＞间层＞乔木层,夏蜡梅灰分含量略低于灌木层灰分含量的平均值;各层次植物平均去灰分热值大小顺序为乔木层＞灌木层＞草本层＞间层,夏蜡梅平均去灰分热值低于间层。多数植物不同季节叶的灰分含量、去灰分热值均以10月最高。     

光强对三叶鬼针草生长特征的影响

利用温室盆栽试验,研究了不同光强100%、40%、20%和5%下三叶鬼针草营养生长期和繁殖期的生长特征。结果表明:中度遮荫有利于三叶鬼针草支持结构的生长和营养期的物质积累,重度遮荫下仍能生长良好。在两个生长时期,相对生长速率(RGR)、净同化速率(NAR)均在100%光强下最大,5%光强下最小;总生物量在营养期和繁殖期分别在40%光强和全光照下最大,在3%光强下最小;株高、总叶面积(TLA)、根生物量比(RMR)、根冠比(R/C)、叶生物量比(LMR)、比叶面积(SLA)、叶面积比(LAR)、平均叶面积比(LARm)在3%光强时均大于全光照下的;支持结构生物量比(SBR)在40%光强、20%光强下大于3%光强和全光照处理。这说明三叶鬼针草在形态、生物量分配及生长特性上对光因素具较强的可塑性,这可能是其分布范围广、具有强入侵性的因素之一。     

光照强度对广西地不容光合特性和生长的影响

以盆栽当年生广西地不容为材料,研究不同光照强度(100%、50%、30%和15%自然光强)对其光合特性和生长的影响。结果表明:随着光照强度的降低,广西地不容最大净光合速率(P_(max))、光饱和点(LSP)、光补偿点(LCP)先减小,而后稍有增大;表观量子效率(AQY)在30%和50%光强下显著高于100%和15%光强处理;叶片叶绿素总量(Chl)、叶绿素a(Chla)、叶绿素b(Chlb)、类胡萝卜素(Car)含量随光强的减弱而增大,Car/Chl随光强的减弱而减小,Chla/Chlb比值在各处理间无显著差异;单叶面积随生长光强的减弱而增大,比叶重(LMA)则随着生长光强的减弱而减小;30%光强下广西地不容块根生物量最高,光照过强和过弱都不利于其生物量的积累。广西地不容对光强的适应范围较广,但光照过强或过荫均对生长造成不良影响,光合速率降低,生长减缓,块根生物量积累下降,30%光强是其当年生苗生长的最佳光强。     

濒危植物银杉幼树对生长光强的季节性光合响应

银杉(Cathayaargyrophylla)是我国松科中特有的单种属植物,被认为处于濒危状态。在对银杉群落多年调查研究的基础上,针对银杉幼树生长过程对光强的需求特性,我们开展了银杉幼树对光的适应性研究。试验在人工培育的银杉苗圃地,采用遮荫的方法设置不同的光环境处理(100%、45%和3%自然光强),利用气体交换技术和叶绿素荧光技术测定了3种光强下银杉叶片光合生理指标的变化,探讨了不同光环境下银杉幼树光合能力在夏季和冬季的变化及其对生长光强的响应等。结果表明:在夏季银杉生长旺盛时期,遮荫导致叶片最大光合速率(Pnmax)、羧化效率(CE)下降,但不同叶龄叶片的下降幅度不同。随生长光强的下降,银杉幼树的光补偿点(LCP)和光饱和点(LSP)有所降低,但全晴天时,低光强(3%自然光强)条件下实际的光辐射量高于当年生叶片光补偿点的累积时间约6h,而且与光饱和的区域相差极大,造成全天碳同化量低,同化物累积少,严重影响了银杉幼树的正常生长。在不同处理中全光强条件下银杉幼树长势最好,45%光强条件下幼树生长减慢。冬季银杉最大光合速率(Pnmax)、羧化效率(CE)值均低于夏季,光补偿点(LCP)和光饱和点(LSP)也较夏季降低。全光照条件下无论是当年生叶片和一年生叶片,在冬季均出现了轻微光抑制现象,适度遮荫有利于银杉抵御冬季光抑制。无论在遮荫或不遮荫条件下,冬季银杉叶片将所吸收的相对过剩光能通过非辐射途径耗散出去,表现出一种光保护策略。     

不同增温处理对夏蜡梅光合特性和叶绿素荧光参数的影响

利用红外线辐射器(Electric radiant infrared heater)设置3个不同增温处理:(1)晚上增温2℃(18:00—翌日6:00);(2)白天增温2℃(6:00—18:00);(3)全天增温2℃;以不做增温处理作为对照,模拟气候变暖对夏蜡梅(Sinocalycanthus chinensis)的光合特性和叶绿素荧光参数的影响。3个季节中,3种增温处理下的夏蜡梅净光合速率(Anet)和最大净光合速率(Amax)均高于对照。表明3种增温处理均可以提高夏蜡梅的光合作用能力。增温处理提高了气孔导度(Gs)、暗呼吸速率(Rd),降低了胞间CO2浓度(Ci)。3种增温处理中,夏蜡梅在3个生长季节的Anet和Amax均以白天增温最大,表明白天增温下夏蜡梅具有最高的光合作用能力。白天增温处理下的表观量子效率(AQY)、光饱和点(LSP)显著高于全天增温、晚上增温以及对照。白天增温和晚上增温使夏蜡梅的相对叶绿素含量显著增加,且白天增温叶绿素相对含量显著高于晚上增温、全天增温及对照。白天增温、晚上增温与全天增温处理下的夏蜡梅的PSⅡ最大光化学效率(Fv/Fm)均显著低于对照,在12:00和14:00时,三者之间存在显著性差异,以白天增温最高,晚上增温次之,全天增温最低。总之,3种增温处理夏蜡梅的光合能力总体上均有不同程度的增强,且在白天增温处理下,夏蜡梅的Anet、Amax值最高,表明白天增温下夏蜡梅具有最高的光合能力,这与白天增温引起的相对叶绿素含量增高、叶片对强光的适应能力加强、较低程度的光胁迫等因素有关。本研究说明未来增温条件下,将提高夏蜡梅的光合生理活性,促进夏蜡梅的生长。     

夏蜡梅属的细胞地理学研究

本文首次报道西美蜡梅(Calycanthus occidentalis)的核型为K(2n)=22=20m(2SAT)+2sm,与美国蜡梅的变种光叶红(C.floridus var.oblongifolius)同属“2A”类型但较为原始,它们都比“1A”的夏蜡梅(C.chinensis)进化,三者由原始到进步的顺序可能为夏蜡梅—→西美蜡梅—→美国蜡梅(光叶红)。夏蜡梅属可能以较原始的夏蜡梅起源于东亚(中国),再东向迁移到北美洲(美国)形成西美蜡梅和美国蜡梅(光叶红)。     

杉木种子萌发及幼苗生长对光强的响应

设置不同光强梯度(透光率分别为100%、40%、20%、10%和5%,光照强度PPFD分别为201.3、77.0、37.5、19.2、9.8 μmol·m^-2·s^-1),研究光对杉木种子萌发和幼苗早期生长的影响,分析杉木种子萌发、幼苗存活、生长、形态响应、生物量积累及其分配格局对不同光环境的响应策略.结果表明: 杉木种子的萌发率、存活率、建植率和萌发指数在不同光强梯度下均有显著差异,且40%的透光率是种子最适萌发条件,萌发率最高,而全光照下存活率和建植率最高;随光照强度的减弱,杉木幼苗茎长增大,根长、子叶长、子叶厚、真叶数呈降低趋势,而基径在各光照强度间无显著差异;总生物量、根生物量、茎生物量、叶生物量均表现为全光照下最大.随着光照强度的减弱,光合组织与非光合组织生物量比、叶生物量比呈降低趋势,茎生物量比呈增加趋势,根冠比和根生物量比无显著差异.弱光环境促进杉木种子萌发,不利于杉木幼苗存活和生长.在弱光环境下,杉木幼苗通过增大茎生物量来提高对弱光环境的耐受力.     

遮荫对水曲柳和蒙古栎光合、生长和生物量分配的影响

为探讨水曲柳(Fraxinus mandshurica)和蒙古栎(Quercus mongolica)苗期对光的适应性及其生长最适光强,设置4种光环境(全光(FL)、75%光(LS)、50%光(MS)、25%光(HS)),观测了2年生水曲柳和蒙古栎苗木气体交换参数、叶绿素含量(Chl)和比叶重(LMA)、生长及生物量的分配。结果表明:随着光强的减弱,2个树种的LMA、单位叶鲜质量(LFA)和根冠比均呈下降趋势;叶绿素含量(Chl)呈上升趋势,且差异显著(p<0.05);光补偿点(LCP)和暗呼吸速率(Rd)呈"N"形变化,但差异均不显著(p>0.05);水曲柳的最大光合速率(Pmax)在HS处理下最大,Rd在HS处理下最小;蒙古栎的最大光合速率(Pmax)在LS处理下最大,Rd也较小;在全光处理下苗高增量均低于HS处理,地径增量均高于HS处理。研究结果进一步确定水曲柳苗期具有一定的耐荫性,在弱光强下生长较好;蒙古栎苗期对光照要求较高,在相对较强光照下生长较好。     

Changes in endogenous levels of three cytokinins during development of excised watermelon cotyledons

We have determined by an immunological method the endogenous levels of three cytokinins: dihydrozeatin riboside (DHZR), transzeatin riboside (tZR) and isope-ntenyladenosine (IPA) in watermelon (Citrullus vulgaris Schrad., cv. Fairfax) cotyledons that were either attached to the seedling or excised from the seed after imbibition and then grown on water. Both seedlings and cotyledons were grown either for 5 days in continuous light or for 3 days in the dark and 2 days in light. Our aim was to verify whether endogenous cytokinin levels are lower in excised than in attached cotyledons as could be expected since excised cotyledons are much more sensitive to exogenous cytokinin application. The levels of the three cytokinins were very low immediately after imbibition, but gradually increased during the following days. They were higher in excised cotyledons after 5 days of culture in the dark than in cotyledons of the same age that had developed on the seedling. Dihydrozeatin riboside was by far the most abundant of the three cytokinins in cotyledons as well as in the hypocotyl and the root.
Irradiation reduced the level of DHZR, negating the concept that light promotes cotyledon development by increasing endogenous cytokinins. Transzeatin riboside when supplied exogenously, stimulated cotyledon development at a lower concentration than the other two cytokinins. Exogenous supply of ben-zyladenine (BA) induced a strong increase in endogenous tZR already after 24 h.     

Light and chlorophyll gradients within Cucurbita cotyledons

Abstract. Measurement of light within 10–14-d-old green and etiolated Cucurbita pepo cotyledons were made with fibre-optic microprobes to assess the influence of chlorophyll distribution and anatomical variations in mesophyll cell type (spongy versus palisade) on internal light pattern. More than 50% of the pigment in green cotyledons occurred in the upper (adaxial) 300 μm and this gradient strongly influenced the internal propagation of 680 nm light. When the upper (adaxial) surface was irradiated with 680 nm light, almost complete absorption occurred within the first 400 μm (palisade) of approximately 1200-μm-thick cotyledons. In contrast, when lower (abaxial) surfaces were irradiated with 680 nm light, penetration extended throughout the spongy mesophyll to about the 700 μm depth. Measurements of collimaled and scattered light gradients at 550, 680 and 750 nm indicated that collimaled light was rapidly scattered by mesophyll cells. In cotyledons irradiated on the upper surface, spongy mesophyll cells received only scattered light. Furthermore, comparisons of scattered light gradients obtained from cotyledons irradiated on upper and lower surfaces suggested that spongy mesophyll cells scatter light more effectively than palisade cells, probably due to the greater proportion of intercellular air spaces in spongy mesophyll tissue. These data also indicate that both the spectral quality and quantity of light incident on palisade versus spongy mesophyll cells differs, perhaps contributing to developmental and physiological differences between these two mesophyll cell types.     

The Role of Cotyledons in Flower Initiation of Pharbitis nil at Low Temperatures

Seedlings of Pharbitis nil, Strains Violet, Tendan and Kidachi,initiated floral buds under Continuous light when exposed totemperatures lower than 15, 15 and 21?C, respectively, throughoutthe experimental period, or to 13–14?C for a minimum durationof 10, 8 and 4 days, respectively. Cotyledons were necessaryfor floral initiation when the seedlings at the start of coldtreatment were 8 days old (10 days old for Kidachi) or younger,although neither cotyledons nor foliage leaves were necessarywhen the plants were older. When the cotyledons in young seedlingswere removed immediately after exposure to cold temperature(13–14?C) for 14 (Violet), 12 (Tendan) or 8 (Kidachi)days (cold treatment begun when the cotyledons had just unfolded),only a few plants initiated floral buds under continuous light.However, when the cotyledons were left attached for 2 more daysat 23?C, the plants produced as many flower buds as those withintact cotyledons, suggesting that cotyledons exposed to coldtemperature produce a floral stimulus which can be translocatedto buds even after the end of the cold treatment. (Received October 14, 1981; Accepted January 20, 1982)     

The Effects of Cytokinins on Unfolding of Cotyledons and Opening of Hypocotylar Hooks of Cucumber

Benzyladenine (BA), zeatin and kinetin caused the unfolding of cucumber (Cucumis sativus L. Var. Jing-ye No. 4) cotyledons. But the other plant hormones e.g. gibberellic acid (GA3), indoleacetic acid(IAA), ethylene (ethrel), abscisic acid (ABA) and other related compound e.g. KCl, adenine were not so. This response was caused by even lower concentration (0.01 ppm). Therefore, it could be used as a bioassay for cytokinins. KCl affaeted synergistically on cytokinin-induced unfolding. Basally applied BA (10 ppm) stimulated the opening of the intact hypocotylar hook. The light affacted synergistically on BA-induced opening. However, basally applied BA prevented the opening of decapitated hooks, especially in the light. The cotyledons were found to play a part of effects in maintaining the hook.     

The role of cotyledons in the establishment of Suaeda physophora seedlings

The role of cotyledons in seedling establishment of the euhalophyte Suaeda physophora under non-saline and saline conditions (addition of 1 mM or 400 mM NaCl) was investigated. Survival and fresh and dry weights were greater for seedlings grown in the light (12-h light/12-h dark) than in the dark (24-h dark). The shading of cotyledons tended to decrease shoot height, shoot organic dry weight, number of leaves, and survival of seedlings regardless of NaCl treatment, but the effect of cotyledon shading was greater with 400 mM NaCl. Concentrations of Na⁺ were higher in cotyledons than in leaves, regardless of NaCl treatment. The K⁺/Na⁺ ratio was lower in cotyledons than in leaves for seedlings treated with 1 mM NaCl but not for seedlings treated with 400 mM NaCl. Addition of 400 mM NaCl decreased oxygen production in cotyledons but especially in leaves. These results are consistent with the hypothesis that, by generating oxygen via photosynthesis and by compartmentalizing Na⁺, cotyledons are crucial for the establishment of S. physophora seedlings in saline environments.     

The role of roots and cotyledons as storage organs in early stages of establishment in Quercus crispula: a quantitative analysis of the nonstructural carbohydrate in cotyledons and roots

Quercus seedlings have hypogeal cotyledons and tap roots, both of which act as storage organs. The importance of the storage function in the two organs may change as the seedling develops. Therefore, changes in carbohydrate reserves in cotyledons and roots of Q. crispula grown under 40 % and 3 % of full light from shoot emergence to the completion of the first leaf flush were monitored. In addition, a shoot-clipping treatment was performed to examine the relative contribution of the cotyledons and tap roots to resprouting. Cotyledons maintained large amounts of nonstructural carbohydrates during shoot development, and carbohydrates were still present in the cotyledons during the final phase of leaf flush. In addition, a notable increase in the amount of carbohydrates was observed in tap roots before leaf flush at both light levels. Since root development occurred before leaf flush, even in plants grown under 3 % light, the carbohydrate found in them presumably originated from seed reserves and was translocated to roots as storage reserves. When shoots were clipped at the leaf flushing stage, the amount of carbohydrate decreased only in the cotyledons after resprouting, suggesting that cotyledons act as the main storage organs during shoot development stages. However, it could be advantageous as a 'risk avoidance strategy' for the seedlings to store reserves in both cotyledons and roots, since cotyledons may be removed by predators during shoot development.     

Development of cytosol and chloroplast aldolases during germination of spinach seeds

The total activity of aldolase (EC 4.1.2.13) and the activities of cytosol and chloroplast aldolase were determined in seeds, cotyledons, primary leaves and secondary leaves of spinach (Spinacia oleracea L., cv. Monopa) during germination. Total aldolase activity in cotyledons increased from low levels to a low maximum in the dark after one week and to a high maximum in white light after three to four weeks and declined thereafter. The activity in primary and secondary leaves started to rise strongly from the 18th and 26th days, respectively, up to the 42nd day of germination. The levels of aldolase activity paralleled the development of leaf area, chlorophyll content and protein content per leaf except that the leaf area of cotyledons continued to increase steadily up to the 42nd day after the maximum of aldolase activity was reached. Resolution of cytosol- and chloroplast-specific isoenzymes by chromatography on diethylaminoethylcellulose indicated that in the light the cytosol enzyme represented approx. 8% of the total activity in cotyledons, primary and secondary leaves throughout germination, and the chloroplast enzyme represented the remaining 92%. Only in cotyledons of dark-grown seedlings was the cytosol aldolase between 25 and 50% of the total activity. Seeds contained almost exclusively a cytosol aldolase. In cotyledons the increase of total activity in the light was specifically the consequence of an increase in chloroplast aldolase while the cytosol aldolase was little affected by light. The light effect was mediated by phytochrome as demonstrated by classical induction and reversion experiments with red and far-red light and by continuous far-red light treatment.Abbreviation DEAE-cellulose diethylaminoethylcellulose     

The effect of cotyledons on hypocotyl elongation in light-grown bean seedlings: Comparison between dwarf and tall varieties

Hypocotyl sections with and without the cotyledons were cutfrom bean seedlings and incubated under white light of 6000lux. The cotyledons had an inhibitory effect as well as a promotiveeffect on hypocotyl growth. The former effect was more strikingin the dwarf variety, and the latter in the tall variety. Whenthe hypocotyl units were exposed to light for shorter times(6 hr or less) or incubated under weaker light (1600 and 50lux), the inhibitory effect of the cotyledons decreased greatly,and in the tall variety the presence of cotyledons producedno inhibition, but a promotion of hypocotyl growth. GA treatmentenhanced hypocotyl growth and counteracted the growth inhibitioncaused by the cotyledons. On the whole, the GA effect was moremarked in the tall variety than in the dwarf. The elongation of bean hypocotyls may be controlled by a balancebetween the inhibitory and promotive effects of cotyledons,and the predominance of the former over the latter may be oneof the causes for expressing dwarfing. (Received November 13, 1976; )