Higher Specific Leaf Mass Research Articles

Effect of herbivory by goats on primary and secondary metabolism of Cocos nucifera L. (Arecaceae) in a semi-arid environment in Brazilian Northeast

The relationship between herbivores and plants has important ecological implications for both organisms and directly affects the plant’s physiological responses, which need to invest in structures and secondary metabolites to overcome the damages. This study aimed to evaluate functional attributes related to the primary and secondary metabolism of Cocos nucifera L. (Arecaceae) submitted to herbivory by goats. Five individuals of C. nucifera were selected in two areas, one with and one without goats. The carbohydrate content, specific leaf mass, and phytochemical screening were obtained, evaluating the presence or absence of saponins, tannins, flavonoids, steroids, alkaloids, and glycosides. The results show that plants under herbivory showed 50% more sugars and a higher specific leaf mass than no-herbivory plants. Also, plants under herbivory showed a higher amount of saponins, steroids, and alkaloids. The production of defense metabolites, which are energetically costly, require the energy supply provided by the carbohydrates produced in photosynthesis; thus, higher levels of sugars were observed in attacked plants. Even under attack, C. nucifera plants allocate resources for biomass production, to increase leaf sclerophylly and hinder herbivory. The investment in saponins, steroids, and alkaloids is related to herbivory, as demonstrated by the analysis of principal components analysis. We conclude that herbivory by goats activates defense responses in C. nucifera plants, making them allocate sugars to produce secondary metabolites.

Biomass growth and development in air-cured burley and flue-cured virginia tobacco varieties

Research on the accumulation and partitioning of biomass in the tobacco cycle is scarce, particularly those comparing different varieties. The objective of this work was to study the partition of biomass in air-cured burley - ACB (BAT2101) and flue-cured virginia - FCV (CSC4704) varieties. In a greenhouse experiment, the two varieties were transplanted into pots containing a mixture of fine sand and substrate (1:1). Samples were taken for a period of 98 days, with 7 day intervals. In each harvest, dry mass and leaf area were measured, and specific leaf mass, leaf area ratio, relative growth rate, net assimilation rate, and root to shoot ratios were estimated. The data showed that carbon partitioning in plants of both varieties is influenced by root growth, which was 50% higher in ACB by the end of the experiment. The higher accumulation of mass in the roots of this variety may be related to the fact that it requires more nitrogen than virginia and, therefore, it could be a mechanism for increased uptake of this element. ACB also had higher specific leaf mass than FCV, which may be related to the body of ACB. This information is important for choosing varieties adapted for field conditions, as well as for the genetic improvement of tobacco. Furthermore, from the point of view of crop management, this knowledge may provide useful information for maximizing leaf growth.

Acclimatization capacity of leaf traits of species co-occurring in restinga and seasonal semideciduous forest ecosystems

Restingas and seasonal semideciduous forests (SSF) are phytophysiognomies of the Atlantic Forest that have many co-occurring species. However, the microclimatic and edaphic conditions of these phytophysiognomies are quite different. Restingas are characterized by low water availability, high irradiance and temperatures, and sandy and nutrient poor soil, which contrasts with the soil conditions of forests. In this sense, these environmental divergences would have forced species to become acclimatized in order to co-occur in these two distinct environments. The present study aimed to determine the main functional leaf traits that enabled Maytenus obtusifolia, Manilkara subsericea and Inga laurina to co-occur in both restinga and SSF. Morphological, physiological, nutritional and biochemical traits of the leaves of these three species in the restinga and SSF were analyzed. The results showed that in the restinga the species possess thicker leaves with a greater thickening of mesophyll cells; the adaxial and abaxial epidermis and cuticle. In addition, restinga leaves had higher specific leaf mass and greater stomatal density, as well as less leaf area than species in the SSF. The restinga species invested in the biosynthesis of osmoregulatory and photoprotective molecules. Photosynthetic performance was similar between phytophysiognomies for M. obtusifolia and M. subsericea, but I. laurina had lower photosynthetic performance in the restinga. We conclude that the species invested in structural, physiological and biochemical adjustments in the restinga in response to conditions of low water availability and high irradiance.

In vitro colchicine-induced polyploid plantlet production and regeneration from leaf explants of the diploid pear (Pyrus communis L.) cultivar, ‘Fertility’

SummaryPolyploid plantlets, including triploid, tetraploid, and mixoploid, were induced from the European pear (Pyrus communis L.) cultivar ‘Fertility’ by in vitro colchicine treatment of leaf explants. The leaf explants were incubated in 0.4% (w/v) colchicine for 24, 48, or 72 h, then transferred to adventitious shoot-induction medium. Regenerated shoots were pre-selected according to their morphological characteristics when compared to control shoots from untreated shoot proliferation cultures. Shoots with putative polyploid morphological characteristics were maintained and proliferated. The ploidy levels of all putative polyploid individuals were analysed by flow cytometry and identified by chromosome counts of shoot tip tissue squashes. Polyploid shoots were rooted, and the resulting plantlets were transferred to the field. Polyploid plantlets had a higher specific leaf mass and larger stomata than those of diploid plantlets.

Physiological and transplanting performance of Quercus ilex L. (holm oak) seedlings grown in nurseries with different winter conditions

Resistance to drought and frost is a requisite for seedling survival and growth in Mediterranean continental areas. Environmental conditions in the nursery influence the functional characteristics of seedlings. We addressed if cultivation in nurseries that experience different winter conditions affected cold hardiness and other functional attributes relevant for transplanting performance of Quercus ilex (holm oak) seedlings. It was hypothesised that plants grown at cold-winter sites have higher stress resistance, vigour, and transplanting performance than the seedlings cultivated in mild-winter sites. We also studied if current root growth activity, determined as the number of white roots on the plug surface, can be used to predict frost hardiness. Seedlings from the same seed lot were cultivated at an inland and a coastal nursery, the former having colder winters than the latter. Cultural practices in both nurseries were similar. On seven dates from mid-summer 2000 to mid-spring 2001, frost damage was assessed by shoot mortality and electrolyte leakage after freezes to either −12 °C or −19 °C. Potential drought tolerance, root growth capacity, plant morphology, shoot nutrient and soluble sugar concentration were determined in late fall and in mid-winter. Seedlings were transplanted at an inland site in late fall and in mid-winter and their survival and growth was measured for 2 years. Coastal plants cold hardened latter in the fall and dehardened earlier in the spring than inland seedlings. In the fall and in early spring, coastal plants had greater frost damage and shoot mortality than inland seedlings at both −12 and −19 °C. In mid-winter, frost damage and shoot mortality after −12 °C did not differ between nurseries but was greater in coastal plants after −19 °C. Inland plants had lower osmotic potential either at full turgor or at the turgor loss point suggesting they were potentially more drought-tolerant. Inland seedlings were bigger, concentrated more shoot N and soluble sugars, and had higher specific leaf mass and root growth capacity than coastal seedlings. Current root growth activity had the same seasonal variation pattern at both locations and did not correlate with frost hardiness. Nursery location did not affect transplanting mortality. However, inland seedlings had greater growth than coastal seedlings when planted in mid-winter planting but not in late fall. This study demonstrates that differences in winter conditions in the nursery have a strong effect on the functional and transplanting performance of Q. ilex seedlings and that current root growth activity cannot be used as a predictor of the frost hardiness in this oak.

Leaf life span and nitrogen content in semideciduous forest tree species (Croton priscus and Hymenaea courbaril)

In comparison to deciduous species, evergreen plants have lower leaf nutrient contents and higher leaf life span, important mechanisms for nutrient economy, allowing the colonization of low fertility soils. Strategies to conserve nitrogen in two semideciduous tropical forest tree species, with different leaf life spans were analyzed. The hypothesis was the fact that the two species would present different nitrogen conservation mechanisms in relation to chemical (total nitrogen, protein, chlorophyll, and proteolytic activity), functional (leaf life span, N-use efficiency, and N-resorption efficiency), morphological (specific leaf mass) leaf characteristics, and total nitrogen in the soil. Hymenaea courbaril L. presented lower nitrogen compounds in leaves, longer leaf life span, higher N-use efficiency, and higher specific leaf mass, while absorbing proportionally less nitrogen from the soil than Croton priscus Croizat. These characteristics can contribute for a better nitrogen economy strategy of H. courbaril. No relationship was found between leaf life span and N resorption efficiency, nor between leaf life span, protease activity and nitrogen mobilization. The electrophoretic profiles of proteolytic enzymes in young leaves of the two species presented more bands with enzymatic activity than other kinds of leaves.

The functional co-ordination of leaf morphology, nitrogen concentration, and gas exchange in40 wetland species

We grew 40 commonly co-occurring species of wetland herbs from eastern North America under uniform conditions to evaluate the overall pattern of interspecific variation in specific leaf mass (SLM), foliar nitrogen content, stomatal conductance (g), and internal leaf CO2 concentration (ci). While the relationship between any two of these traits that influence net photosynthetic rate is constrained to some degree, there is sufficient flexibility to allow the evolution of different but more or less equally effective interrelationships among these central elements of leaf form and function. We use contemporary techniques of structural equation modelling to describe the general nature of such evolutionary diversification in leaf form and function among these wetland plants. Our model essentially extends the Cowan-Farquhar model of stomatal regulation to include relationships between SLM and foliar nitrogen. The model can take two forms, with variables expressed as either per unit leaf area or per unit leaf mass. When variables are expressed on an areal basis, the model predicts that a species with a higher SLM will have a higher foliar nitrogen level. The foliar nitrogen level, in accordance with the Cowan-Farquhar model, in turn determines the dynamics of stomatal regulation in relation to the marginal cost of water loss relative to carbon gain. The dependence of stomatal regulation on foliar nitrogen also determines the maximal rates of stomatal conductance and net photosynthesis. Internal CO2 concentrations within the leaf follow as a necessary consequence of these interrelationships. This areal-based model describes the data for the 35 C3 wetland species well; the same basic model applies to the five C4 species in our sample, except for shifts in the quantitative effects of net photosynthetic rate and stomatal conductance on internal CO2 levels. When the variables are expressed on a mass basis, a slightly different model results, as net photosynthetic rate decreases directly with SLM and is not related to species level variation in either leaf nitrogen concentration or maximal stomatal conductance. Both forms of the model indicate the need to advance our understanding of the ecological and evolutionary basis for variation in SLM, including its association with traits such as leaf demography and canopy architecture as well as environmental characteristics of the habitats where particular species predominate.

Differences in Leaf Cuticle Structure and Efficacy among Eastern Redbud and Mexican Redbud Phenotypes

The objective of this study was to compare the structure and efficacy in terms of retarding cuticular transpiration of leaf cuticles from eastern redbud (Cercis canadensis L.) and dull-leaf and glossy-leaf Mexican redbud [Cercis canadensis var. mexicana (Rose) M. Hopk.]. Leaves of Mexican redbud exhibited several xeromorphic characteristics compared to eastern redbud: a smaller, thicker leaf with thicker cuticles, more cuticular wax, a higher specific leaf mass, and greater hydrated water content on a leaf area basis. Mexican redbuds with a glossy leaf differed from those with a dull leaf only in a thicker adaxial cuticle lacking wax crystallite on the surface. Epicuticular wax crystallite were present on the abaxial surface of all leaves examined. Detached leaves of eastern redbud had a higher water loss rate than those of Mexican redbud only on a dry mass basis, not on a leaf area basis. There was no difference in the rate of water loss by detached leaves of glossy-leaf and dull-leaf Mexican redbuds after 4 hours.

Growth analysis of UV‐B‐irradiated cucumber seedlings as influenced by photosynthetic photon flux source and cultivar

A growth analysis was made of ultraviolet‐B (UV‐B)‐sensitive (Poinsett) and insensitive (Ashley) cultivars of Cucuumis satives L. grown in growth chambers at 600 μmol m−2 s−1 of photosynthetic photon flux (PPF) provided by red‐ and far‐red‐deficient metal halide (MH) or blue‐ and UV‐A‐deficient high pressure sodium/deluxe f HPS/DX) lamps. Plants were irradiated 6 h daiiy with 0.2 f‐UV‐B) or 18.2 C+UV‐B) kJ m−2 day−1 of biologically effective UV‐B for 8 or 15 days from time of seeding. In general, plants given supplemental UV‐B for 15 days showed lower leaf area ratio (LARs, and higher specific leaf mass (SLM) mean relative growth rate (MRGR) and net assimilation rate (NAR) than that of control plants, but they showed no difference in leaf mass ratio (LMR), Plants grown under HPS/DX lamps vs MH lamps showed higher SLM and NAR. lower LAR and LMR. hut no difference in MRGR. LMR was the only growth parameter affected by cultivar: at 15 days, it was slightly greater in Poinsett than in Ashley. There were no interactive effects of UV‐B. PPF source or cultivar on any of the growth parameters determined, indicating that the choice of either HPS/DX or MH lamps should not affect growth response to UV‐B radiation. This was true even though leaves of UV‐B‐irradiated plants grown under HPS/DX lamps have been shown to have greater chlorosis than those grown under MH lamps.

Influence of Inverse Day/Night Temperature on Ozone Sensitivity and Selected Morphological and Physiological Responses of Cucumber

Cucumis sativus L. (cvs. Poinsett and Ashley) plants were grown from seed in a growth chamber at a +10C (28/18) or a -10C (18/28) difference (DIF) between day temperature (DT) and night temperature (NT) on a 12-hour photoperiod for 24 days prior to ozone (O3) fumigation (3 hours at 0.5 umol·mol-1). Negative DIF, compared to +DIF, reduced plant height, node count, fresh weight, dry weight, and leaf area in both cultivars. Photosynthetic rate (Pn), chlorophyll concentration, and variable chlorophyll fluorescence (Fv) were lower and O3 injury and polyamine concentrations were higher at -DIF than at +DIF. Ozone fumigation generally increased leaf concentration of polyamines and reduced Pn, stomatal conductance, and chlorophyll fluorescence. `Poinsett' generally had a higher specific leaf mass and higher concentrations of chlorophyll a and polyamines than did `Ashley', but there was no cultivar difference in O3 injury, growth response, Pn, or stomatal conductance.

Photosynthetic and structural acclimation to light direction in vertical leaves of Silphium terebinthinaceum.

The azimuth of vertical leaves of Silphium terebinthinaceum profoundly influenced total daily irradiance as well as the proportion of direct versus diffuse light incident on the adaxial and abaxial leaf surface. These differences caused structural and physiological adjustments in leaves that affected photosynthetic performance. Leaves with the adaxial surface facing East received equal daily integrated irradiance on each surface, and these leaves had similar photosynthetic rates when irradiated on either the adaxial or abaxial surface. The adaxial surface of East-facing leaves was also the only surface to receive more direct than diffuse irradiance and this was the only leaf side which had a clearly defined columnar palisade layer. A potential cost of constructing East-facing leaves with symmetrical photosynthetic capcity was a 25% higher specific leaf mass and increased leaf thickness in comparison to asymmetrical South-facing leaves. The adaxial surface of South-facing leaves received approximately three times more daily integrated irradiance than the abaxial surface. When measured at saturating CO2 and irradiance, these leaves had 42% higher photosynthetic rates when irradiated on the adaxial surface than when irradiated on the abaxial surface. However, there was no difference in photosynthesis for these leaves when irradiated on either surface when measurements were made at ambient CO2. Stomatal distribution (mean adaxial/abaxial stomatal density = 0.61) was unaffected by leaf orientation. Thus, the potential for high photosynthetic rates of adaxial palisade cells in South-facing leaves at ambient CO2 concentrations may have been constrained by stomatal limitations to gas exchange. The distribution of soluble protein and chlorophyll within leaves suggests that palisade and spongy mesophyll cells acclimated to their local light environment. The protein/chlorophyll ratio was high in the palisade layers and decreased in the spongy mesophyll cells, presumably corresponding to the attentuation of light as it penetrates leaves. Unlike some species, the chlorophyll a/b ratio and the degree of thylakoid stacking was uniform throughout the thickness of the leaf. It appears that sun-shade acclimation among cell layers of Silphium terebinthinaceum leaves is accomplished without adjustment to the chlorophyll a/b ratio or to thylakoid membrane structure.

GROWTH ANALYSIS OF UV-B IRRADIATED CUCUMBER SEEDLINGS AS INFLUENCED BY PAR SOURCE AND CULTIVAR

A growth analysis was made of UV-B sensitive (`Poinsett') and insensitive (`Ashley') cultivars of Cucumis sativus L. grown in growth chambers at 600 μmol m-2 s-1 of photosynthetically active radiation (PAR) provided by red- and far-red-deficient metal halide (MH) or blue- and UV-A- deficient high pressure sodium/deluxe (HPS/DX) lamps. Plants were irradiated 6 h daily with 0.2 (-UV-B) or 18.2 (+UV-B) kJ m-2 d-1 of biologically effective UV-B for 15 days from time of seeding. In general, plants given +UV-B vs. -UV-B treatment showed lower specific leaf area (SLA) and leaf area ratio (LAR), higher specific leaf mass (SLM), mean relative growth rate (MRGR), and net assimilation rate (NAR), and no difference in leaf mass ratio (LMR). Plants grown under HPS/DX lamps vs. MH lamps had higher SLM and NAR, lower SLA, LAR, and LMR, and no difference in MRGR. Cultivar affected only LMR. PAR source and/or cultivar did not affect plant response to UV-B radiation.

Genetic Variation in Leaf Morphology and Plant and Tissue Water Relations During Drought in Cercis canadensis L

Abstract Genetic variation in plant and tissue water relations in response to drought, and in leaf morphology, were examined in greenhouse-grown Cercis canadensis L. (eastern redbud) seedlings originating from seed obtained in three contrasting habitats: a relatively xeric Kansas prairie, a Kansas gallery forest understory, and a relatively mesic Indiana understory. Kansas prairie redbud maintained significantly greater leaf conductance (gwv) during a 13-day drought than did Kansas and Indiana understory redbud, despite similar decreases in leaf water potential (Ψleaf) in all three sources. Moreover, Kansas prairie redbud had significantly lower osmotic potentials at full and zero turgor compared to Indiana redbud at both the early and later stages of drought. Kansas understory redbud was the only source to undergo a significant decrease in relative water content at zero turgor and the bulk modulus of elasticity during drought. Kansas prairie redbud leaves were smaller and thicker and had higher specific leaf mass (i.e., more xerophytic) than understory redbud leaves. Kansas understory redbud had intermediate characteristics in terms of gwv; at the early to middle stages of drought, osmotic potentials at high and low Ψleaf and leaf area and thickness compared to Kansas prairie and Indiana understory redbud. These results suggest that genetically controlled physiological and morphological adaptation has occurred in redbud that should facilitate its survival in greatly contrasting habitats. For. Sci. 34(1):200-207.

Physiological plasticity in water relations and leaf structure of understory versus open-grown Cerciscanadensis in northeastern Kansas

Field and laboratory studies were used to evaluate physiological plasticity in water relations and leaf structural characteristics of CerciscanadensisL. (redbud) saplings growing in a gallery forest understory and an adjacent prairie in eastern Kansas. Two study periods were defined based on high (greater than −0.2 MPa in May) and low (−1.5 MPa in July) predawn soil water potential (ψsoil). Leaf conductance to water vapor diffusion (gwv) was greater for prairie than understory redbud saplings during both sampling periods (maximum gwv = 7.5–8.7 mm s−1). Moreover, gwv for prairie redbud remained high at both high and low ψsoil, but was significantly lower for understory redbud during midday at low ψsoil. Transpiration flux was also higher in the prairie than in the understory site and reached a maximum for prairie redbud (318 mg m−2 s−1) in July, in conjunction with high leaf to air vapor pressure deficits (maximum, 5.3 kPa). Leaf water potential declined significantly at both sites with decreased ψsoil and the minimum values (−3.0 MPa) were recorded in understory redbud. Leaves of prairie redbud were significantly smaller, thicker, and had higher specific leaf mass and stomatal density than leaves of understory redbud, which are consistent with differences between xeric and mesic species, respectively. These differences in water relations and leaf morphology between understory and prairie redbud suggest a high degree of physiological plasticity for this species in eastern Kansas.