Physiological and Ecological Studies in the Analysis of Plant Environment: X. An Analysis, of the Effects of Seasonal Variation in Daylight and Temperature on the Growth of Helianthus annuus in the Vegetative Phase

To determine on a quantitative and mathematical basis the effectsof seasonal changes in the levels of daylight and temperatureon vegetative growth and development in two years pot experimentsin the open were carried out at successive weekly intervalsbetween May and September. So as to minimize errors arisingfrom ontogenetic drifts the procedure adopted was to sow atintervals of a few days throughout the season batches of potswith seed of Helianthus annuus and to select pots containingplants of a standard morphological status for the start of eachweekly experiment. At the beginning and end of the week halfthe pots were harvested, the plants divided into root, stem,and leaf, the leaf area estimated, and the dry weights determined.The diurnal changes in air temperature were continuously recordedwhile the amount of daylight, excluding infra-red and ultravioletradiation, was measured with a specially constructed integratingrecorder. From the biological data for each week twelve variables werecalculated, namely the relative growth rates of both the wholeplant and the individual parts, the proportion by dry weightof the individual parts (root-, stem-, and leaf-weight ratios),the ratio of leaf area to total plant weight (leaf-area ratio),the rate of leaf expansion, the ratio of leaf area to leaf weight,and the net assimilation rate on the criteria of leaf area andweight. The main independent variables considered were the meanweekly temperature, the mean daily maximum minus the mean nightlyminimum temperature, the total amount of light per week, andthe time of year when the individual experiment was undertaken. Multiple regression analyses showed that (i) save for the stem-weightratio the data for the two years could be pooled, (ii) the fluctuationin diurnal temperature was of little account, (iii) transformationof the light data to either logarithms or square roots did notimprove the fit and (iv) for some of the dependent variables,e.g. leaf-area ratio, the ‘time of year’ effectwas significant but could be eliminated if the equation wasmodified to predict the value at the end of the week, giventhe initial value and the light and temperature data. The final series of multiple regressions revealed that (i) theleaf-weight ratio is not controlled by either the amount oflight or mean temperature, (ii) the relative growth rate ofthe root and the root-weight ratio are positively linked onlywith temperature, (iii) the rate of leaf growth either in areaor weight together with the net assimilation rate (area basis)are positively dependent on light alone, (iv) the net assimilationrate (weight basis) and the relative growth rates of the wholeplant and the stem are directly and positively correlated withboth temperature and light, and (v) the leaf-area ratio, theratio of leaf area to leaf weight and the stem-weight ratioare depressed by increasing light but augmented by rising temperature.In the individual regressions for net assimilation rate (areaand weight), the relative growth rates of the whole plant, stemand leaf weight, and the ratios of stem weight and leaf areato leaf weight the percentage variation accounted for rangedfrom 47 to as high as 91 per cent. The implication of these findings in relation to experimentsin controlled environmental chambers are discussed.     

Growth Analysis of Sweet Pepper (Capsicum annuum L.): 1. The Influence of Irradiance and Temperature under Glasshouse Conditions in Winter

A growth analysis was carried out with sweet pepper grown ina glasshouse. The plants received natural daylight or additionalillumination applied either during or after the natural photopenod.All irradiance conditions were applied at three temperatureregimes. Additional illumination increased leaf number, leaf area andtotal dry weight. At all temperatures the long-day treatmentsshowed a smaller number of leaves, but a larger leaf area whencompared to the short-day treatments with the same daily radiationsum. A lower temperature progressively reduced leaf area. The derived growth analysis quantities showed strong ontogenetictrends. When comparing both methods of applying additional illuminationhigher mean relative growth rates were observed for the long-daytreatments, especially at the lowest temperature. No differencesin mean net assimilation rate were found, but the short-daytreatments showed a reduced mean leaf area ratio. A lower nighttemperature decreased RGR and NAR but did not affect LAR, alower day temperature increased NAR and decreased LAR. Changesin LAR were largely mediated by changes in specific leaf weight. Capsicum annuum L., sweet pepper, growth analysis, irradiance, temperature     

Morphological variation in Eichhornia azurea (Kunth) and Eichhornia crassipes (Mart.) Solms in relation to aquatic vegetation type and the environment in the floodplain of the Rio Paraná, Brazil

Eichhornia azurea and E. crassipes are the most frequent dominants of aquatic vegetation in the floodplain of the Upper Rio Paraná in Brazil. Morphological traits of samples collected at sites where they dominated the vegetation were measured and compared between vegetation types identified in the floodplain. Total leaf weight, specific leaf area and the leaf to root weight ratio of E. azurea and total leaf dry weight, total leaf area and total plant dry weight of E. crassipes differed significantly between vegetation types from 1999. Pearson correlation coefficients indicated a number of significant relationships between morphological traits and environmental variables. Five E. azurea traits increased linearly with water depth and four with water clarity. The leaf to root weight ratio also increased linearly with sediment iron and calcium content. E. crassipes total root dry weight and total plant dry weight were respectively quadratically related to sediment calcium and the euphotic proportion of the water column. Total leaf dry weight and total plant dry weight increased linearly with water depth while remainder dry weight decreased linearly with sediment phosphorus content.     

Growth and physiological responses of canola (Brassica napus) to three components of global climate change: temperature, carbon dioxide and drought

Elevated CO₂ appears to be a significant factor in global warming, which will likely lead to drought conditions in many areas. Few studies have considered the interactive effects of higher CO₂, temperature and drought on plant growth and physiology. We grew canola ( Brassica napus cv. 45H72) plants under lower (22/18°C) and higher (28/24°C) temperature regimes in controlled-environment chambers at ambient (370 μmol mol⁻¹) and elevated (740 μmol mol⁻¹) CO₂ levels. One half of the plants were watered to field capacity and the other half at wilting point. In three separate experiments, we determined growth, various physiological parameters and content of abscisic acid (ABA), indole-3-acetic acid and ethylene. Drought-stressed plants grown under higher temperature at ambient CO₂ had decreased stem height and diameter, leaf number and area, dry matter, leaf area ratio, shoot/root weight ratio, net CO₂ assimilation and chlorophyll fluorescence. However, these plants had increased specific leaf weight, leaf weight ratio and chlorophyll concentration. Elevated CO₂ generally had the opposite effect, and partially reversed the inhibitory effects of higher temperature and drought on leaf dry weight accumulation. This study showed that higher temperature and drought inhibit many processes but elevated CO₂ partially mitigate some adverse effects. As expected, drought stress increased ABA but higher temperature inhibited the ability of plants to produce ABA in response to drought.     

Effects of seismic stress on the vegetative growth of Glycine max (L.) Merr. cv. Wells II

Abstract. Vegetative plants of soybean [ Glycine max (L.) Merr. cv. Wells II] grown in a greenhouse and agitated periodically on a gyratory shaker had shorter stems, less leaf area, and lower leaf and plant dry weight than did undisturbed greenhouse-grown (GG) plants after 16 d of treatment. Outdoor-grown (OG) plants, which were subjected to additional environmental stresses including ultraviolet radiation, wind loading, and uncontrolled temperature and humidity fluctuations, were smaller and had less dry weight than GG controls, but growth was not inhibited further by gyratory shaking. Periodic shaking of GG soybeans resulted in the same plant and leaf dry weight as for OG soybeans. Response of GG plants to mechanical stress depended on light intensity, with minimum growth reduction occurring under full light (FL) level, and maximum growth reduction occurring under lower light levels (24–45% FL). Reduction in dry weight gain due to mechanical stress corresponded to a decrease in relative growth rate (RGR). Decreases in net assimilation rate and leaf area ratio contributed equally to the lower RGR of shaken plants, indicating that seismic stress inhibits dry weight accumulation by decreasing both the photosynthetic efficiency and the assimilatory surface of soybean.     

Quantitative analyses of shade-shoot architecture of conifers native to New Zealand

Shoot architecture was quantified by measuring the "maximum silhouette area ratio" (R_max). R_max was calculated from the maximum silhouette area (or projected area) of the intact shoot, divided by the silhouette area of the leaves or phylloclades (leaf-like flattened stems) when they are removed from the shoot and laid out flat. Like conifers of the Northern Hemisphere (NH) with non-appressed foliage, the R_max of shade-adapted shoots ranged from 0.5 to 1.0 in New Zealand (NZ) conifers with non-appressed foliage. Defining a "leaf" to mean either a true leaf or a phylloclade, the following was found: leaf area/leaf dry weight, leaf area/shoot dry weight, and leaf dry weight/shoot dry weight, were all similar in the shade-shoots of NZ and NH conifers. None of these variables were significantly correlated with R_max in the NZ conifers, unless species with leaves averaging less than 4 mm² in size were excluded from the analyses. Foliage dry weight/shoot projected area was strongly correlated with R_max. NZ conifers had both smaller and larger mean leaf sizes in comparison to NH conifers. The mean projected area per shade-adapted leaf of NZ conifers varied from 2.7 to 436 mm². In NH conifers, the mean projected area per shade leaf varied from 12 to 83 mm². Except for the strikingly larger range in leaf size in NZ conifers, the data support a hypothesis of strong convergent evolution of shade-shoot architecture in NZ and NH conifers. The results are discussed in relation to photosynthesis, stand production, and the ecological distribution of conifers.     

不同光照条件下三七幼苗形态及生长指标的变化

用遮阳网设置不同透光率(自然全光照的1%、3%、8%、12%和22%)处理,对不同光照条件下三七〔Panax notoginseng(Burk.)F.H.Chen〕幼苗形态指标(株高、冠幅、块根长、主根长、块根直径、茎基径、单株须根数和单株须根长)、干物质积累(不同器官干质量)和分配以及叶片性状(单株叶面积、比叶面积和叶绿素相对含量SPAD值)的变化进行了研究。结果表明:在透光率不同的条件下三七幼苗的形态指标、不同器官干质量及分配以及叶片性状均有明显变化。其中,块根直径、单株须根长、单株须根数、不同器官(块根、须根、根、叶片和茎)干质量和植株总干质量均随透光率增大逐渐提高;株高在透光率22%条件下最高;冠幅和单株叶面积在透光率3%条件下最大;主根长、茎基径、根冠比、根质比及SPAD值均在透光率8%条件下最高;茎质比和叶质比在透光率3%和1%条件下较大;比叶面积随透光率增大逐渐降低。综合分析结果揭示:三七是一种典型的喜阴植物,种植过程中适当遮阳有利于其生长和干物质积累,其中透光率8%对三七幼苗生长较为适宜。     

Effects of Aphis fabae and Uromyces viciae-favae on the growth of a susceptible and an aphid resistant cultivar of Vicia faba

Damaging effects of either black bean aphid (Aphis fabae), broad bean rust (Uromyces viciae-fabae), or the combination of both were investigated on a susceptible (cv. Diana) and an aphid resistant (cv. Bolero) cultivar of Vicia faba. When compared with rust, aphids caused greater reductions of root dry weight, shoot dry weight, leaf area, and mean relative growth rate. The mean unit leaf rate was also reduced whereas the leaf area ratio was not affected. The damage caused per aphid was highest on the susceptible cultivar. Rust induced damage did not differ between the cultivars. Concomitant infestation with both pests only resulted in additive damage. The population development of aphids was delayed on partially resistant plants. High temperature and rust infection reduced the total number of aphids the plants were able to support but not the level of resistance. Thus the specific damaging effect per aphid was increased.     

遮光和施氮对暗紫贝母形态特征和生物量分配的影响

根据最优分配理论( optimal partitioning theory,OPT),在自然环境中,由于地上和地下资源在空间上的分离,陆生植物需要调整其地上和地下部分的生物量分配以平衡对资源的吸收。研究结果[1-2]显示：在植物地上资源严重受限时,叶片的生物量分配相对增加;而地下资源严重受限时,根的生物量分配相对增加。然而,植物的生物量分配对资源的响应较为复杂。首先,除了生物量分配,形态变化也是植物调节资源吸收的重要手段,例如,植物通过增加比叶面积提高对光照的吸收,通过调整比根长响应土壤养分的变化[3-4];并且,一些植物甚至以形态响应为主,生物量分配的变化并不明显[3,5]。此外,某些植物还有一些特殊的资源平衡方式,例如,克隆植物通过构件之间的养分传输平衡资源在空间上的分配不均[6];拥有特化储藏器官的植物可依靠大量储藏物质来平衡资源在时间上的分配不均[7]。植物所具有的丰富的资源响应方式决定了其多样的资源策略。     

岷江上游干旱河谷矮探春叶片特征与环境因子的关系

对岷江上游干旱河谷矮探春(Jasminumhumile L.)的叶片形态解剖特征进行了显微观察,分析了海拔梯度上叶片形态与环境因子的关系。结果表明,矮探春叶片呈长椭圆形,叶肉组织分化明显;随着海拔升高,叶面积、厚度、干重、饱和含水量、海绵组织厚度,中脉厚度以及厚角组织厚度/中脉厚度之比(M/C)等呈增大趋势,而栅栏组织厚度/海绵组织厚度之比(P/S)则减小;叶片长/宽比、表皮厚度、栅栏组织厚度和比叶重在海拔梯度上无明显差异。叶面积、干重、饱和含水量、叶厚度和海绵组织厚度等参数两两之间呈显著正相关,而它们与P/S均呈显著负相关。叶面积、干重、海绵组织厚度和M/C等主要受土壤含水量的影响,并随着土壤含水量增加而增大;P/S随着土壤含水量和年降水量增加而减小;叶片厚度、饱和含水量和中脉厚度均随着温和度的降低而增大。岷江上游干旱河谷区土壤水份和生长季温度可能是影响矮探春叶片形态解剖特征的主要因子。     

Leaf area ratio and net assimilation rate of 24 wild species differing in relative growth rate

Summary Which factors cause fast-growing plant species to achieve a higher relative growth rate than slow-growing ones? To answer this question 24 wild species were grown from seed in a growth chamber under conditions of optimal nutrient supply and a growth analysis was carried out. Mean relative growth rate, corrected for possible ontogenetic drift, ranged from 113 to 356 mg g^–1 day^–1. Net assimilation rate, the increase in plant dry weight per unit leaf area and unit time, varied two-fold between species but no correlation with relative growth rate was found. The correlation between leaf area ratio, the ratio between total leaf area and total plant weight, and relative growth rate was very high. This positive correlation was mainly due to the specific leaf area, the ratio between leaf area and leaf weight, and to a lesser extent caused by the leaf weight ratio, the fraction of plant biomass allocated to the leaves. Differences in relative growth rate under conditions of optimum nutrient supply were correlated with the soil fertility in the natural habitat of these species. It is postulated that natural selection in a nutrient-rich environment has favoured species with a high specific leaf area and a high leaf weight ratio, and consequently a high leaf area ratio, whereas selection in nutrient-poor habitats has led to species with an inherently low specific leaf area and a higher fraction of root mass, and thus a low leaf area ratio.     

Growth Analysis of Sweet Pepper (Capsicum annuum L.): 2. Interacting Effects of Irradiance, Temperature and Plant Age in Controlled Conditions

A growth analysis was carried out with sweet pepper plants grownin a phytotron. Irradiance conditions were: 0.84 or 3.25 MJm^–2 in 8 h, 1.67 MJ m^–2 in 16 h and 2.51 MJ m^–2in 24 h. Temperatures applied were 25 or 21 °C during thephotoperiod in combination with 25, 21 and 17 or 21, 17 and13 °C respectively during the nyctoperiod. Highest values for leaf area and total dry weight were foundwhen applying 1.67 MJ m^–2 in 16 h, followed by 3.25 MJm^–2 in 8 h, irrespective of the temperature regime. Continuousirradiance ultimately resulted in leaf drop. A reduction inthe day temperature decreased leaf area and total dry weight.At a day temperature of 25 °C the dry weight increased withdecreasing night temperature when applying 3.25 MJ m^–2in 8 h. At a day temperature of 21 °C leaf area and dryweight were reduced when 17 or 13 °C were applied duringa 16 h nyctoperiod. Values for relative growth rate, net assimilation rate, leafarea ratio and leaf weight ratio strongly decreased with advancingplant age. The effects of irradiance treatment on RGR and NARwere analogous to those on total dry weight while the reversepattern was observed for the LAR. A decrease in day temperaturedecreased the RGR. The effects of night temperature exhibitedstrong interactions with day temperature and photoperiod. Theinfluence of temperature on RGR was largely mediated throughchanges in the LAR. The latter parameter was highly correlatedwith the specific leaf weight. Capsicum annuum L., sweet pepper, growth analysis, irradiance, temperature, plant age     

不同灌水量对2个蓝浆果品种幼苗生长和耗水规律的影响及相关性分析

以兔眼蓝浆果(Vaccinium ashei Reade)品种'Brightwell'和南方高丛蓝浆果(V.corymbosum hybrids)品种'Misty'为研究对象,研究不同灌水量〔50%WC、75%WC、100%WC(CK)和125%WC〕(WC为单株日耗水量)对幼苗生长、单株耗水量的日变化和月变化、单株净增干质量、总耗水量和水分利用效率的影响,并采用回归分析法对单株月耗水量与月均温和月均空气相对湿度的相关性进行分析.结果显示:随灌水量提高,2个品种幼苗的地径、单株枝长和单株总叶面积的增量总体上均不断增大,但单株枝长增量略有波动;单株根、茎、叶和总干质量总体上均逐渐增大,根冠比则逐渐减小;单株净增干质量和总耗水量均随灌水量提高而增大,而水分利用效率则在50%WC条件下最低、在75%WC条件下最高.在相同灌水量条件下,品种'Misty'幼苗的地径和单株枝长的增量,单株茎、叶和总干质量及水分利用效率基本上均高于品种'Brightwell',而其单株总叶面积增量、单株根干质量、根冠比和总耗水量却基本上低于后者.在7月份至9月份,2个品种幼苗单株耗水量的日变化基本上呈单峰曲线,但其单株耗水量峰值出现的时间段则因品种和灌水量不同而异;在全天不同时间段和不同月份,2个品种幼苗的单株耗水量均随灌水量提高而增大;在相同灌水量条件下,品种'Misty'幼苗的单株耗水量总体上低于品种'Brightwell'.回归分析结果表明:2个品种幼苗的单株月耗水量与月均温呈显著或极显著正相关,与月均空气相对湿度呈显著或极显著负相关.综合分析结果表明:蓝浆果幼苗的耗水量不但与品种特性有关,而且还受到土壤水分含量、气温和空气湿度的影响;在相同灌水量条件下,品种'Brightwell'幼苗的耗水量高于品种'Misty',但其水分利用效率却低于后者.在中国南方地区,品种'Brightwell'和'Misty'的适宜灌水量分别为100%WC和75%WC.     

Effect of Temperature on Growth of Crotalaria juncea L. and Crotalaria sericea Retz.

Growth performances of Crotalaria juncea L. and C. sericea Retz.have been compared at two controlled temperatures, 16–20°C, and 28–32 °C, with respect to increase ind. wt and leaf area, relative growth rate, leaf area ratio,specific leaf area, leaf weight ratio, net assimilation rate,the ratio of mean relative growth rate to mean relative rateof leaf area increase () and shoot/root ratios. Both the speciesgrew better at the higher temperature; however the relativegrowth rate was more affected by temperature in C. sericea thanin C. juncea. Further, it was observed to be more dependenton net assimilation rate than on the leaf area ratio. Crotalaria juncea L., Crotalaria sericea Retz., relative growth rate, leaf area ratio, specific leaf area, leaf weight ratio, leaf area increase, net assimilation rate, shoot/root ratio     

Responses of dry weight growth under SO2 stress in an SO2-tolerant plant,Polygonum cuspidatum

The effects of exposure to 0.5–0.7 ppm SO₂ for about one month on the dry weight growth and net photosynthesis ofPolygonum cuspidatum were investigate. Furthermore, the carbon and nitrogen concentrations in each plant organ were measured. The results obtained showed no significant decrease in the total dry weight of SO₂-treated plants in comparison with controls. On the other hand, the leaf area (LA) and/or leaf dry weight of SO₂-treated plants were increased, and the root dry weight (RW) was decreased, in comparison with controls. The leaf carbon assimilation rate (CAR) in SO₂-treated plants was slightly decreased in spite of a clear decrease in net photosynthesis, and the value of (SW+RW)/LA (SW stem dry weight) was decreased in comparison with controls, thus minimizing the reduction in CAR. Furthermore, the ratio of total leaf carbon absorption (leaf area x CAR) to total root nitrogen absorption (root dry weight x nitrogen assimilation rate) in SO₂-treated plants was similar to that in controls. From these results, it can be concluded that an increase in leaf area and/or leaf dry weight and a decrease in root dry weight inP. cuspidatum under SO₂ stress may be induced in order to compensate for the decrease in CAR and to maintain the ratio of total leaf carbon absorption to total root nitrogen absorption in the early stage of vegetative growth.     

狭叶红景天幼苗对水分及遮阴的生长及生理生化响应

研究植物对水分和遮阴胁迫的响应及其生理机制对制定合理的栽培管理措施十分必要。以红景天属植物为研究对象,设置土壤含水量分别为田间持水量的80%(过湿水分)、70%(正常水分)、60%(轻度干旱)、40%(中度干旱)、20%(重度干旱)5个水分梯度;设置2个遮阴处理,以全光照(遮阴率为0)为对照、黑色遮阴网遮阴(遮阴率为85%),研究狭叶红景天生长及生理生化指标的变化特征。结果表明:在不同水分处理下,与对照相比,叶绿素含量、茎干重和茎重比(SMR)显著增加(P0.05),株高、总生物量、叶面积、叶干重、叶重比(LMR)、比叶面积(SLA)、叶面积比(LAR)和叶面积根干重比(LARMR)增加,根冠比和根重比(RMR)减少;随着干旱程度加剧,丙二醛(MDA)、脯氨酸(Pro)和可溶性糖(Ss)含量增加,超氧化物歧化酶(SOD)活性总体呈先增加后减小的趋势。在遮阴处理下,株高、SMR、SLA、LAR和LARMR显著增加(P0.05),叶绿素SPAD值和叶面积增加,总生物量、根干重、根冠比和LMR显著减少(P0.05),茎干重和叶干重减少,MDA含量显著增加,Pro含量略有下降,Ss含量减少。在水分胁迫下,狭叶红景天中度干旱时通过增加酶活性抵御伤害,重度干旱超过其阈值,SOD活性下降,植物体受到伤害,Ss可能是主要的渗透调节物质。在遮阴处理下,狭叶红景天通过增加SLA避免遮阴伤害。狭叶红景天在受到环境胁迫时会通过形态改变、调节MDA含量、抗氧化酶活性和渗透调节物质来保证自身正常的生长发育。     

The Application of Growth Analysis to Structured Experimental Designs and a New Procedure for Estimating Unit Leaf Rate and its Variance

A method is presented for estimating relative growth rates andother growth parameters using data from randomized block designs,prior to conventional or functional growth analysis. This methodcan be extended to other experimental designs where an additivemodel is applicable. The effects of this approach are illustratedusing the most commonly derived growth quantities, relativegrowth rate, leaf area ratio and unit leaf rate (net assimilationrate), from an extensive data set available for the growth ofthe biennial Arctium tomentosum. Comparisons are made betweendifferent growth analytical techniques and a new procedure fordetermining unit leaf rate, with a rigorous statistical treatment,is presented for the particular case when the logarithms ofthe variates for leaf area and total dry weight are linearlyrelated. Arctium tomentosum, burdock, growth analysis, randomized block design, unit leaf rate, relation of leaf area and total dry weight     

The Effects of Light and Temperature on Germination and Growth of Luffa aegyptiaca

The effects of light and temperature on the germination and growth of Luffa aegyptiaca were investigated both in the laboratory and in the field. The seeds germinated in both darkness and light but germination was better in the light. At constant temperatures germination was best at 21°C, while alternating temperatures of 21 and 31°C and 15 and 41°C caused higher germination than the most favourable constant temperature. Constant temperatures of 15 and 31°C and alternating temperatures of 21 and 41°C resulted in very low germination, whereas no germination occurred at 41°C and at alternating temperatures of 31 and 41°C. Soil depth caused only a delay in seed germination, as it did not affect the total germination. High temperature and high light intensity resulted in good seedling growth in terms of dry weight, leaf area and relative growth rate. High temperature and low light intensity caused increased plant height and high shoot weight ratio, both of which manifested in seedling etiolation. They also caused high leaf area ratio. Under low temperatures, irrespective of light intensity, growth was generally poor, but it was significantly poorer under low light intensity, which also caused high root weight ratio. High light intensity was principally responsible for high leaf weight ratio. The results help to explain the abundance of the species in newly cleared areas in Lagos and its environs.     

The role of seed provenance in the early development of Arbutus unedo seedlings under contrasting watering conditions

In the last decades, several studies have reported the increase of land degradation and desertification in the Mediterranean Basin. Depending on degradation severity, ecological restoration might be needed in order to promote ecosystem recovery. The ecology of the selected species and intra specific variability should be considered in order to improve restoration options, especially facing climate change.The present study tested the hypothesis that seedlings from drier provenances would be better adapted to low water content conditions. Seeds were germinated under controlled temperature after which seedlings were grown in a phytotron under two contrasting watering regimes. Seedling performance was analysed using morphological and physiological parameters.Low water content had a clear negative effect on the seedlings’ aboveground biomass (total dry weight, root collar diameter, leaf dry weight and leaf weight ratio) and a positive effect on belowground biomass (root weight and root:shoot ratio). This response was not unequivocal, since provenances differed in morphological adaptations to low water content. Seedlings from the wettest provenance revealed a higher relative growth rate under high water content but a poor adaptation to limited water availability when compared to the other two provenances. This was observed by the absence of a significant belowground investment in this provenance. Seedlings from the wettest provenance also presented a significant reduction of total leaf area that was not observed in the other two provenances. This can however be hardly considered as a successful adaptation to cope with drought since this provenance produced less sclerophyllous leaves, less belowground biomass and also lower sapwood to leaf area ratio independently from the water content conditions. By contrast, seedlings from the dry provenance with the hottest summer had similar root collar diameter, leaf dry weight and physiological performance under both watering regimes.The observed adaptations to water regimes seem to be related with the climate of the seed source and highlighted the importance of seed provenance in ecological restoration actions using Mediterranean species. This knowledge could improve early establishment success predictions for different plant populations, allowing more reliable and cost-effective management decisions under climate change scenarios.     

The Vegetative Growth of Helianthus annuus and Phaseolus vulgaris as Affected by Seasonal Factors in Freetown, Sierra Leone

Sand-culture experiments were carried out in full daylight atsuccessive weekly intervals between March and December 1969,to investigate the effects of seasonal changes in climatic factorson the growth of Helianthus annuus and Phaseolus vulgaris inFreetown. Values for a number of growth parameters were calculatedfrom the dry weights of the leaves, stems, and roots, and fromthe leaf areas. Simultaneously the diurnal changes in climaticfactors were recorded. Multiple regressions linking light, temperature, and relativehumidity with some of the growth parameters were calculated.The total variance accounted for in the regressions of relativegrowth-rate, net assimilation rate, and leaf weight ratio onlight, temperature, and relative humidity ranged from 51 to60 per cent in P. vulgaris. In H. annuus relative humidity wasless important; the percentage proportion of total varianceaccounted for in the regression of leaf weight ratio (and leafarea ratio in both species) on light and temperature was notsignificant. The results showed that H. annuus grew faster than P. vulgaris,but the latter's growth was depressed less by the dull weatherof the rainy season. The relative growth-rates of both specieswere positively dependent on light and temperature while theirnet assimilation rates were negatively dependent on relativehumidity, and their leaf area ratios negatively dependent onlight. All parameters used except leaf area ratio and leaf areato leaf weight ratio showed seasonal variations correspondingto dry and rainy seasons. The initial and final values of leafarea ratio and weight ratios were always different but did notvary in the same direction in both species. The results are discussed in relation to similar work done elsewhere.