Total Leaf Surface Area Research Articles

Leaf Conductance of Primary and Mature Leaves of Pinus roxburghii: A Comparison

We used a null-balance porometer to measure leaf conductance of mature and primary leaves of natural seedlings, saplings, and trees of Pinus roxburghii (chir) during autumn at four sites at 1,320–1,930 m elevation in the central Himalaya of India. Our hypothesis that primary leaves had higher leaf conductance than mature leaves (needles in fascicles), based on measurements in other pines, was rejected. Comparisons on the same saplings and seedlings showed lower leaf conductance for primary leaves than for mature leaves. Primary leaves on seedlings and saplings also did not consistently have higher leaf conductance than mature leaves on near-by trees. Mature leaves on seedlings, however, did often have higher conductance than mature leaves on nearby trees. Mean values for leaf conductance (mmol m−2 s−1, based on total leaf surface area) ranged from 42–82 for mature leaves on trees, 60–121 for mature leaves on seedlings, and 28–67 for primary leaves on seedlings. Compared to published values for other pine species, conductance of mature leaves ofP. roxburghii is relatively low.

Photosynthesis, photoinhibition, and nitrogen use efficiency in native and invasive tree ferns in Hawaii.

Photosynthetic gas exchange, chlorophyll fluorescence, nitrogen use efficiency, and related leaf traits of native Hawaiian tree ferns in the genus Cibotium were compared with those of the invasive Australian tree fern Sphaeropteris cooperi in an attempt to explain the higher growth rates of S. cooperi in Hawaii. Comparisons were made between mature sporophytes growing in the sun (gap or forest edge) and in shady understories at four sites at three different elevations. The invasive tree fern had 12-13cm greater height increase per year and approximately 5times larger total leaf surface area per plant compared to the native tree ferns. The maximum rates of photosynthesis of S. cooperi in the sun and shade were significantly higher than those of the native Cibotium spp (for example, 11.2 and 7.1µmolm-2s-1, and 5.8 and 3.6µmolm-2s-1 respectively for the invasive and natives at low elevation). The instantaneous photosynthetic nitrogen use efficiency of the invasive tree fern was significantly higher than that of the native tree ferns, but when integrated over the life span of the frond the differences were not significant. The fronds of the invasive tree fern species had a significantly shorter life span than the native tree ferns (approximately 6months and 12months, respectively), and significantly higher nitrogen content per unit leaf mass. The native tree ferns growing in both sun and shade exhibited greater photoinhibition than the invasive tree fern after being experimentally subjected to high light levels. The native tree ferns recovered only 78% of their dark-acclimated quantum yield (Fv/Fm), while the invasive tree fern recovered 90% and 86% of its dark-acclimated Fv/Fm when growing in sun and shade, respectively. Overall, the invasive tree fern appears to be more efficient at capturing and utilizing light than the native Cibotium species, particularly in high-light environments such as those associated with high levels of disturbance.

Control of transpiration in three coffee cultivars: the role of hydraulic and crown architecture

Water use and hydraulic architecture were studied in the coffee (Coffea arabica) cultivars San Ramon, Yellow Caturra and Typica growing in the field under similar environmental conditions. The cultivars differed in growth habit, crown architecture, basal sapwood area and total leaf surface area. Transpiration per unit leaf area (E), stomatal conductance (g s), crown conductance (g c), total hydraulic conductance of the soil/leaf pathway (G t) and the stomatal decoupling coefficient, omega (Ω) (Jarvis and McNaughton 1986) were assessed over a range of soil moisture and during partial defoliation treatments. The relationship between sap flow and sapwood area was linear and appeared to be similar for the three cultivars. Variation in g c, E, and G t of intact plants and leaf area-specific hydraulic conductivity (k l) of excised lateral branches was negatively correlated with variation in the ratio of leaf area to sapwood area. Transpiration, g c, and g s were positively correlated with G t. Transpiration and G t varied with total leaf area and were greatest at intermediate values (10 m2) of leaf area. Omega was greatest in Yellow Caturra, the cultivar with the greatest leaf area and a dense crown, and was smallest in Typica, the cultivar with an open crown. Differences in omega were attributable primarily to differences in leaf boundary layer conductance among the cultivars. Plants of each cultivar that were 40% defoliated maintained sap flows comparable to pretreatment plants, but expected compensatory increases in g s were not consistently observed. Despite their contrasting crown morphologies and hydraulic architecture, the three cultivars shared common relationships between water use and hydraulic architectural traits.

Water utilization, plant hydraulic properties and xylem vulnerability in three contrasting coffee (Coffea arabica) cultivars.

Water use, hydraulic properties and xylem vulnerability to cavitation were studied in the coffee (Coffea arabica L.) cultivars San Ramon, Yellow Caturra and Typica growing in the field under similar environmental conditions. The cultivars differed in growth habit, crown morphology and total leaf surface area. Sap flow, stomatal conductance (g(s)), crown conductance (g(c)), apparent hydraulic conductance of the soil-leaf pathway (G(t)), leaf water potential (Psi(L)) and xylem vulnerability to loss of hydraulic conductivity were assessed under well-watered conditions and during a 21-day period when irrigation was withheld. Sap flow, g(c), and G(t) were greatest in Typica both with and without irrigation, lowest in San Ramon, which was relatively unresponsive to the withholding of irrigation, and intermediate in Yellow Caturra. The cultivars had similar g(s) when well watered, but withholding water decreased g(s) more in Typica and Yellow Caturra than in San Ramon. Typica had substantially lower Psi(L) near the end of the unirrigated period than the other cultivars (-2.5 versus -1.8 MPa), consistent with the relatively high sap flow in this cultivar. Xylem vulnerability curves indicated that Typica was less susceptible to loss of hydraulic conductivity than the other cultivars, consistent with the more negative Psi(L) values of Typica in the field during the period of low soil water availability. During soil drying, water use declined linearly with relative conductivity loss predicted from vulnerability curves. However, cultivar-specific relationships between water use and predicted conductivity loss were not observed because of pronounced hysteresis during recovery of water use following soil water recharge. All cultivars shared the same functional relationship between integrated daily sap flow and G(t), but they had different operating ranges. The three cultivars also shared common functional relationships between hydraulic architecture and water use despite consistent differences in water use under irrigated and dry soil conditions. We conclude that hydraulic architectural traits, rate of water use per plant and crown architecture are important determinants of short- and long-term variations in the water balance of Coffea arabica.

Ecology of Aglaia mackiana (Meliaceae) Seedlings in a New Guinea Rain Forest1

The large seeds of Aglaia mackiana (Meliaceae) germinate and produce vigorous seedlings under closed canopies or in large gaps. To assess seedling ecology after germination, we measured growth, herbivore damage, and survivorship of seedlings over one year. The sample included shaded seedlings from dispersed seeds, undispersed seeds under parent trees, and seedlings transplanted to gaps. We quantified the light environment using hemispherical canopy photographs taken above seedlings at the beginning and end of the one–year study. Seedlings transplanted to gaps grew faster and had more leaves, larger total leaf surface area, longer secondary roots, and greater root mass than shaded seedlings. Seedlings in gaps did not differ from shaded seedlings in survivorship or amount of herbivore– and pathogen–caused leaf damage. The canopy photographs taken one year apart suggest there is a rough equilibrium in closed canopies with slight changes occurring around an average light level. Sites with 0.06 ISF tended to close; few gaps grew larger. Seedlings under parenr trees and seedlings away from parent trees had similar amounts of leaf damage and virtually identical survivorship after 18 months, but seedlings under parent trees had slower growth rates and smaller total leaf surface areas. Dispersal did not strongly benefit seeds via escaping high levels of mortality or comperition around the parent.

Corner's rules revisited: ontogenetic and interspecific patterns in leaf–stem allometry

We studied interspecific and ontogenetic relationships between the size of a leaf and the primary diameter of the internode bearing it. Although these two variables are known to be strongly correlated across species, the form of this relationship has not been studied. In a re‐analysis of published data on interspecific comparisons of 69 temperate tree species, we showed the existence of a strong relationship between twig cross‐sectional area (before secondary growth) and surface area of leaves borne by it, within each of three morphological groups, deciduous angiosperms, evergreen angiosperms, and gymnosperms. Within each of these groups, this relationship is isometric: across species, primary cross‐sectional area of the stem increases proportionally with leaf surface area. When we consider the relationship between the cross‐sectional area of a twig and the surface area of one leaf borne by it, the y‐intercepts for this relation are different for the three groups. However, when total leaf surface area per first‐year shoot is considered, no differences remained between gymnosperms and evergreen angiosperms, but deciduous angiosperms continued to be distinct. This difference between deciduous and evergreen groups could be due to differences in leaf volume (evergreen species have thicker leaves than deciduous) or in traits related to a trade‐off between life span of leaves and their physiological behaviour.We present results of the first quantitative study of the relationship between leaf size and primary diameter of the stem during ontogeny. Both these parameters increase during development of the plant from seedling to adult. For the four tree species examined, the relationship between primary cross‐sectional area of the stem and leaf surface area is also isometric.These results bear on a functional interpretation of the relationship between leaf and stem dimensions, suggesting that vascular supply is directly proportional to the requirements of leaves supported by the stem.

Interaction Between Powdery Mildew and N and K Fertility in Begonia

Nine fertility treatments, consisting of a 3 × 3 factorial arrangement of three N rates (30, 120, 240 μg·ml–1) and three K rates (30, 120, 240 μg·ml–1), were applied by constant liquid feed to cuttings of Hiemalis begonia `Hilda' grown in 15-cm plastic pots containing 7.5 peat: 2.5 perlite medium. Prior to transplanting, one-half of the plants were naturally inoculated with Erysiphe cichoracearum to induce powdery mildew infection; while the remaining plants received weekly application of Bayleton (Triadimefon). Shoot growth in fungicide-treated plants increased with increasing rates of both N and K, with highest dry matter production (≈8.0 g/plant) with either 120N–240K or 240N–120K. Disease development in plants treated with fungicide was slight, averaging < 7% of the total leaf surface area infected with mildew, irrespective of N and K rates. Shoot dry weights in inoculated plants were markedly repressed, averaging 3.1 g/plant, as disease occurrence was extensive in all treatments. Significant interactions between N and K fertility affected mildew development in inoculated plants. At the high rate of N, K nutrition had little effect on mildew rating, whereas at 30N and 120N, mildew counts decreased with increasing K rate up to 120 K.

SEASONAL CHANGES OF ROOT HYDRAULIC CONDUCTANCE (KRL) IN FOUR FOREST TREES : AN ECOLOGICAL INTERPRETATION

This paper deals with the possibility of relating root hydraulic parameters to an ecological index describing the continentality/oceanicity of four forest trees. Root hydraulic conductance ($K_R$) of seedlings of Fagus sylvatica L., Quercus ilex L., Quercus suber L. and Quercus pubescens Willd. was measured in May, August and November 1996. $K_R$ was calculated in terms of the relation of the water flow through intact root systems in situ measured with the pressure chamber, and the pressure driving the flow. The sufficiency of the root system to supply the foliage was estimated by dividing $K_R$ by the seedlings leaf surface area ($A_L$) thus obtaining $K_RL$. In the spring, $K_RL$ was largest in F. sylvatica and smallest in Q. pubescens with intermediate values recorded in Q. ilex and Q. suber. All the species studied showed a large decline in $K_RL$ just prior to the winter rest except for Q. suber which mantained $K_RL$ approximately constant through the period of study. In most cases, $K_RL$ changed in accordance with analogous changes in the flow. When the total seedlings' leaf surface area ($A_L$) was plotted versus $K_RL$, it appeared that $K_RL$ of Q. pubescens increased with $A_L$, proportionally, while $K_RL$ of F. sylvatica was inversely related to $A_L$. This, together with the largest $K_RL$ recorded in the summer in Q. pubescens, was interpreted as advantageous to this species (which is adapted to semi-arid environments) in that: (a) roots could supply water to foliage efficiently even during the adverse season and (b) the foliage growth could be sustained even in summer.

Carbon distribution and aboveground net primary production in aspen, jack pine, and black spruce stands in Saskatchewan and Manitoba, Canada

The objectives of this study are to (1) characterize the carbon (C) content, leaf area index, and aboveground net primary production (ANPP) for mature aspen, black spruce, and young and mature jack pine stands at the southern and northern Boreal Ecosystem‐Atmosphere Study (BOREAS) areas and (2) compare net primary production and carbon allocation coefficients for the major boreal forest types of the world. Direct estimates of leaf area index, defined as one half of the total leaf surface area, range from a minimum of 1.8 for jack pine forests to a maximum of 5.6 for black spruce forests; stems comprise 5 to 15% of the total overstory plant area. In the BOREAS study, total ecosystem (vegetation plus detritus plus soil) carbon content is greatest in the black spruce forests (445,760–479,380 kg C ha−1), with 87 to 88% of the C in the soil, and is lowest in the jack pine stands (68,370–68,980 kg C ha−1) with a similar distribution of carbon in the vegetation and soil. Forest floor carbon content and mean residence time (MRT) also vary more among forest types in a study area than between study areas for a forest type; forest floor MRT range from 16 to 19 years for aspen stands to 28 to 39 years for jack pine stands. ANPP differs significantly among the mature forests at each of the BOREAS study areas, ranging from a maximum of 3490 to 3520 kg C ha−1 yr−1 for aspen stands to 1170 to 1220 kg C ha−1 yr−1 for jack pine stands. Both net primary production (NPP) and carbon allocation differ between boreal evergreen and deciduous forests in the world, suggesting global primary production models should distinguish between these two forest types. On average, 56% of NPP for boreal forests occurs as detritus and illustrates the need to better understand factors controlling aboveground and below‐ground detritus production in boreal forests.

Polycyclic Aromatic Hydrocarbon Accumulation in Urban, Suburban, and Rural Vegetation

Polycyclic aromatic hydrocarbons (PAH) partition from the atmosphere to vegetation, soil, water, and sediment. In an effort to quantitate vegetation's ability to scavenge PAH, we collected vegetation samples from urban, suburban, and rural locations during the summer and fall of 1995 and determined PAH burdens (ng/cm2) on a mass per total leaf surface area basis. The total PAH burdens in the rural vegetation samples were, on average, 10 times lower than in the urban samples, confirming that atmospheric PAH burdens are higher near presumed source regions. We also compared the individual PAH burden profiles for urban, suburban, and rural samples. All samples had similar profiles for fluorene, phenanthrene, fluoranthene, and pyrene, while the rural samples were depleted of anthracene, benz[a]anthracene, and several higher molecular weight PAH. In order to calculate a PAH to vegetation mass balance for the northeastern region of the United States, we divided this land area into rural, suburban, and urban clas...

Long-term effects of a doubled atmospheric CO2concentration on the CAM speciesAgave deserti

To examine the effects of a doubled atmospheric CO2 concentration and other aspects of global climate change on a common CAM species native to the Sonoran Desert, Agave deserti was grown under 370 and 750//mol CO2 mol 1 air and gas exchange was measured under various environmental conditions. Doubling the CO2 concentration increased daily net CO2 uptake by 49% throughout the 17 months and decreased daily transpiration by 24%, leading to a 110% increase in water-use efficiency. Under the doubled CO2 concentration, the activity of ribulose1,5-bisphosphate carboxylase/oxygenase (Rubisco) was 11 % lower, phosphoenolpyruvate carboxylase was 34% lower, and the activated:total ratio for Rubisco was 25% greater than under the current CO2 concentration. Less leaf epicuticular wax occurred on plants under the doubled CO2 concentration, which decreased the reflectance of photosyntheti c photon flux [PPF); the chlorophyll content per unit leaf area was also less. The enhancement of daily net CO2 uptake by doubling the C02 concentration increased when the PPF was decreased below 25 mol m~2 d~ when water was withheld, and when day/night temperatures were below 17/12 °C. More leaves, each with a greater surface area, were produced per plant under the doubled CO2 concentration. The combination of increased total leaf surface area and increased daily net CO2 uptake led to an 88% stimulation of dry mass accumulation under the doubled CO2 concentration. A rising atmospheric C02 concentration, together with accompanying changes in temperature, precipitation, and PPF, should increase growth and productivity of native populations of A. deserti.

AROMATIC COMPOUNDS AND WATER RELATIONS OF SOUR ORANGE SEEDLINGS.

Sour orange seedlings were grown in water culture to which one of seven aromatic compounds, associated with allelopathic effects, was added to produce concentrations ranging from 0.5 to 2.0 mM. Leaf water potential (ψ1), leaf stomatal conductance (gs), and whole plant transpiration (T) were measured during a 7-day treatment period. At the end of that period, the total and average leaf surface area, shoot elongation, and fresh weight gain of seedlings were determined. Solutions of vanillic, coumaric, and ferulic acids of 2mM concentration reduced ψ1, gs, and T. Reductions of gs, and T but not (ψ1) occurred when vanillic acid of 1mM concentration was applied. Solutions of vanillic (0.5; 1.0; 2.0mM), coumaric (1; 2mM), cinnamic (1mM), or chlorogenic (1; 2mM) acids reduced fresh weight gain of seedlings. Only the coumaric and chlorogenic acids treatments of 2mM concentration reduced shoot elongation. No treatment affected total or individual leaf area. Gallic and caffeic acids had no effect on sour orange water relations and growth.

Gas exchange and canopy structure of 9-year-old loblolly pine, pitch pine and pitch x loblolly hybrids

Seasonal gas exchange and canopy structure were compared among 9-year-old loblolly pine (Pinus taeda L.), pitch pine (Pinus rigida Mill.), and pitch x loblolly hybrids (Pinus rigida x taeda) growing in an F2 plantation located in Critz, Va., USA. Leaf net photosynthesis, conductance, internal CO2 concentration (ci), water use efficiency (WUE; photosynthesis/conductance), dark respiration and the ratio of net photosynthesis/respiration did not vary among or within the three taxa. Significant differences in volume production, crown length, total crown leaf surface area and the silhouette area of shade shoots among the taxa were observed. The loblolly-South Carolina source had greater volume and crown surface area than the pitch pine, and the hybrid taxa were intermediate between the two. Although the silhouette area ratio of shade foliage varied among taxa, it was not related to volume. A strong relationship between total leaf surface area and volume was observed. Leaf conductance, ci, WUE and leaf water potential were the physiological parameters significantly and positively correlated with volume. This study suggests that the amount of needle surface in the canopy is more important in early stand volume growth than the leaf carbon exchange rate and the degree of needle self-shading in the lower canopy.

Variability of Leaf Chlorophyll Content in a Population of Sassafras

(...) Sassafras displays leaves in a few discrete categories of form. Leaves with entire margins predominate at the proximal and distal nodes of shoots while lobed leaves are most common at the intermediate nodes. In regression analysis for individual trees, leaf nodal position accounted for 30-50% of the variance in chlorophyll content. Leaves of the intermediate nodes 6 through 11 (ca. 46% of all leaves) accounted for 59.3% of total leaf surface area and had the highest chlorophyll content per unit mass and per unit area. (...)

COMPARISON OF TETRAPLOID AND SINGLE GENE‐INDUCED GIGAS VARIANTS IN CHICKPEA (CICER ARIETINUM). II. MORPHOLOGICAL AND ANATOMICAL LEAF CHARACTERS

Two genomic variants of a chickpea (Cicer arietinum L.) parental line have been developed which exhibit gigas characters. The two genotypes were the result of a single‐gene mutation (gigas) and induced tetraploidy of a single parental line. The two genotypes plus parental strain were investigated to determine the similarity‐of‐effect of polyploidy and this single‐gene mutation on leaf anatomy and morphology. Leaves consisted of two rows of alternatively arranged leaflets. Both the tetraploid and parental lines had the same mean number of leaflets per leaf while the gigas plants had fewer, but mean total leaf surface area was greater in the gigas plants. Quantitative comparison of mesophyll and vascular tissue and air space volume density (Vv) showed that leaves of the tetraploid plants had the greatest mesophyll cell density (Vvm) and least air space density. Mesophyll cell density was equal in the parental and single‐gene mutant while parental leaves had the greatest vascular tissue density. The greater mesophyll cell density values of the polyploid were due to larger mean mesophyll cell size, not to greater cell numbers per unit area. Leaf models based on tissue density and leaflet size showed tetraploid plants had the greatest productivity potential per unit of leaflet surface area. However, if models were based on a whole leaf, gigas plants had the greatest productivity potential since they had larger total leaf area. The effectiveness of using structural models to predict physiological potential in plant tissues will be tested in future studies.

Influence of krummholz mat microclimate on needle physiology and survival

Microclimate and photosynthesis of krummholz mat growth forms of Picea engelmanii (Parry) and Abies lasiocarpa [Hook.] Nutt. were investigated to determine structural features which may aid survival in alpine environments. The structure of krummholz mats was described in terms of the vertical distribution of leaf area index and leaf area density, which exceeded 50 m-1 (based on total leaf surface area) near the canopy surface and approached zero below 30 cm from the surface in both species. Photosynthetic photon flux density (PPFD, 0.4-0.7 μm wavelengths) and wind decreased by an average of 6 and 50-fold, respectively, between 1 m above and 10 cm below mat surfaces in both species. Needle temperatures on a P. engelmannii krummholz mat during July averaged about 2°C above air temperature during the day, with a maximum overtemperature of greater than 20°C above T air during one sunlit period. At night, needle temperatures averaged 3-4°C below T air.Net photosynthesis in year-old P. engelmannii shoots reached a maximum at 15-20°C during July and August. Surface shoots were light saturated at near 1200 μmoles m-2s-1 PPFD, and had higher photosynthetic rates than subsurface, predominantly shaded shoots above 800 μmoles m-2s-1. Shade shoots had higher photosynthetic rates when PPFD was below 600 μmoles m-2s-1, and at 250 μmoles m-2s-1 shade shoots maintained about 50% of the net photosynthetic rate of sun shoots at light saturation. Shade shoots appeared capable of benefitting photosynthetically from elevated temperatures within krummholz mats despite relatively low light levels. Especially rapid photosynthesis may occur when canopy needles are illuminated by sunflecks and needle temperatures rise by 10° C or more.Snow cover appears crucial for the survival of needles during winter. Snow accumulated within krummholz needle canopies before the sub-canopy zone of unfoliated branches became filled. The concentrated needle growth in the krummholz canopy captured snow in early autumn without support from ground-level snowpack. Early snow cover in both species prevented cuticle abrasion and resulted in high winter needle water contents and viabilities for subsurface compared to surface needles which became abraded, severely dehydrated, and had high mortality between December and February, especially on windward sides of shoots.Extremely high concentrations of needles within krummholz mat canopies created an aerodynamic structure which elevated needle temperatures to more optimal photosynthetic levels in summer and resulted in more efficient snow accumulation in winter. These factors appear crucial for winter needle survival. Thus, krummholz mats appear to be an important adaptation in growth form which provides survival benefits in both summer and winter.

Relationships between leaf growth and holes caused by herbivores

There are two approaches to the estimation of herbivory in a canopy. One is to measure the absolute amount consumed by herbivores in terms of bites of leaf tissue removed and express defoliation as metres squared of leaf surface area (or kilogram of photosynthetic tissue). This approach is useful for examining the population dynamics and feeding behaviour of the insects or, in a sense, to approach herbivory from a herbivore's perspective. The second is to measure the proportion of leaf area missing, usually expressed as a percentage of total leaf surface area. The latter approach was used for long-term studies of herbivory in Australian rainforests (Lowman 1982, 1984, 1985). and is currently in use for similar studies on eucalypt canopies (Lowman & Heatwole 1987, unpubl. data). One of the most frequently asked questions regarding defoliation measurements expressed as percentage leaf area losses is: 'Does the proportion of area of defoliation stay the same as a leaf expands?' Many herbivores exhibit marked preference for young leaf tissue (Lowman & Box 1983; Selman & Lowman 1983; Wint 1983). A direct measurement (cm2) of holes in mature leaves, therefore. may be an overestimation of the actual amount ingested by herbivores that fed upon young, partially expanded leaves. A proportional estimate of defoliation will remain accurate throughout the life of a leaf, however, if leaf holes expand at the same rate as leaf area. This was tested on young leaves of one species of a northern temperate forest. Liriodendron tullpifera L. (albeit with deciduous, and unusual tulip-shaped leaves), and its holes expanded at a rate proportional to leaf growth (Reichle et al. 1973). In this study, a similar test was performed for a range of Australian rainforest tree species exhibiting different leaf shapes, textures, and growth habits.

Aryl esters of indolebutyric acid increase root regeneration in 3-0 red oak seedlings

Dormant 3-0 red oak seedlings (Quercusrubra L.) were given a 3-s basal dip in 20 mM solutions of indole-3-butyric acid (IBA), the potassium salt of IBA (K-IBA), N-phenyl indolyl-3-butyramide (NP-IBA), phenyl indole-3-thiolobutyrate (P-ITB), or phenyl indolyl-3-butyrate (P-IBA). Seedlings dipped in water or 95% ethanol served as controls. Fifty-six days after treatment, seedlings treated with NP-IBA and P-ITB regenerated up to 3 times more roots (48.7 and 40.0 roots, respectively) than did ethanol-treated control seedlings, which regenerated 14.3 roots. Seedlings treated with P-IBA regenerated 26 roots per seedling. Seedlings treated with NP-IBA and P-ITB had smaller leaves than IBA- and K-IBA treated seedlings. NP-IBA treated seedlings had more leaves than IBA- or K-IBA treated seedlings (155.3 vs. 59 and 53.3, respectively), but had similar leaf surface area. P-ITB-treated seedlings had similar numbers of leaves as IBA- and K-IBA-treated seedlings, but leaves were smaller in size, resulting in less total leaf area. P-IBA-treated seedlings had the greatest total leaf surface area, 1509 cm2; water- and ethanol-treated seedlings had total leaf surface areas of 1271 and 866 cm2, repectively.

Physiological ecology of lodgepole pine (Pinuscontorta) in an enriched CO2 environment

Relatively little work has been done to evaluate the effects of chronically high levels of carbon dioxide on growth and physiology of woody plants. In this study, seedlings of lodgepole pine (Pinuscontorta Dougl. var. latifoliaEngelm.) were grown for 5-month periods at 330, 1000, or 2000 μL CO2•L−1. Height growth; leaf area production; biomass of leaves, stems, and roots; and photosynthetic responses to changing light, moisture, and CO2 concentration were measured. Significant differences between treatments were found in mean seedling height on all measurement dates. Seedlings grown at 1000 μL CO2•L−1 were tallest, with seedlings grown in 2000 μL•L−1 intermediate between the control (330 μL•L−1) and 1000 μL•L−1 treatments. The same relationship was found in production of total leaf surface area. Increased leaf surface area yields a productive advantage to seedlings grown at concentrations of CO2 up to 2000 μL•L−1 even if no increase in net photosynthesis is assumed. Biomass of stems, roots, and secondary leaves was increased in both elevated CO2 conditions, with root biomass approximately 15 times greater in seedlings grown at 1000 μL•L−1 than in those grown at 330 μL•CO2•L−1. Stomatal resistances were essentially the same for all treatments, indicating no CO2-induced stomatal closure to at least 2000 μL•L−1. Photosynthetic Vmax (milligrams per square decimetre per hour) for light response curves varied with CO2 concentration. If results are extrapolated beyond a 5-month period and into field conditions, it appears that size of trees, interactions with competitors, and ecological role of the species might be altered.

Influence of Warm Night Temperatures on Growth and Flowering of Primula x polyanthus

Abstract Plants of Primula x polyanthus Hort. grown at 20°C night temperature had more flowers and leaves but shorter peduncles than at 10°. Area of individual leaves was smaller for plants grown at 20° compared with 10°, but total leaf surface area was the same for 10° or 20°. No difference was observed in dry weight or flowering time.