Specific Leaf Mass Research Articles

Leaflet phenotypic plasticity in three woody species in two strata of a gallery forest

ABSTRACT Background: Along the vertical canopy profile, natural light availability is variable and may induce leaves morphophysiological changes due to phenotypic plasticity. Morphological changes in juvenile and adult leaflet of compound leaves of plant species is still poorly understood, including in woody species of gallery forests. The present study evaluated the leaflet morphophysiological characteristics and plasticity index of three woody species in canopy and understory leaves in a gallery forest. Results: All morphophysiological characteristics varied within species (Myracrodruon urundeuva Allemao, Copaifera langsdorffii Desf. and Tapirira guianensis Aubl.). The leaflets of canopy trees showed significantly higher values of petiole length (PL) and diameter (PD), leaflet thickness (fresh - FT and dry - DT), specific leaf mass (SLM), in relation to understory leaflets. On the other hand, relative water content (RWC) did not change between adult trees and saplings, except for T. guianensis. The plasticity index of leaflet characteristics varied significantly within species. Plasticity index of three morphophysiological characteristics (PL, PD and DT) varied between species. PL and PD had the highest plasticity index values across species, whereas RWC had the lowest plasticity.. Conclusion: Plasticity index of the tree species associates these leaflet morphophysiological traits (PL, PD and DT) with variations in the physical environment between strata of a gallery forest.

Effect of light stress on Crotalaria spectabilis (Fabaceae) and on its herbivore insect, the moth Utetheisa ornatrix (Erebidae: Arctiinae)

ABSTRACT The Plant Stress Hypothesis predicts that stressed plants are more attacked by herbivorous insects. In this work, we investigated the influence of light stress on Crotalaria spectabilis Roth (Fabaceae) and on its main herbivore, the moth Utetheisa ornatrix (L., 1758) (Erebidae: Arctiinae). Specifically, we verified whether plants stressed by shading differ from non-stressed plants in terms of productivity, morphological characteristics and water percentage. We also evaluated the performance of moths in stressed and non-stressed plants. Seeds were sown in pots. When the plants reached 50 cm in height, they were randomly divided into two groups: stressed plants (treatment group) and non-stressed plants (control group). The stressed plants were covered by a black mesh, providing 50% of shading. Eight characteristics of stressed and non-stressed C. spectabilis plants were evaluated: height, fresh and dry aerial biomass, number of pods and seeds, leaf hardness, number of trichomes, leaf area, specific leaf mass and percentage of leaf water. Moths were raised individually on leaves of stressed and non-stressed plants and we obtained the larval survival, larval development time, pupal weight and female fecundity. The non-stressed plants had significantly higher percentage of water in the leaves, greater fresh aerial biomass and a higher number of trichomes than the stressed plants. The survival rate was 98% for larvae raised on leaves from stressed plants and 92% on leaves from non-stressed plants. The larval developmental time was significantly shorter and the weight of female pupae significantly higher in non-stressed plants than in stressed plants. Thus, the Plant Stress Hypothesis was only corroborated by two tested variables: number of trichomes (lower in stressed plants) and larval survival (higher in stressed plants). Trichomes are among the main types of plant defenses against herbivory and reducing their number on leaves would make stressed plants more susceptible to attack by moth larvae, a fact corroborated by a greater larval survival. One of the possible explanations for the lack of corroboration of the Plant Stress Hypothesis for most of the variables tested is that other characteristics can be changed under stress conditions, such as the concentration of secondary compounds.

Individual and interactive effects of temperature and light intensity on canola growth, physiological characteristics and methane emissions

Earlier studies have shown that plants produce methane (CH4) under aerobic conditions, and that this emission is not microbial in nature. However, the precursors of aerobic CH4 remain under debate, and the combined effects of environmental factors on plant-derived CH4 requires further attention. The objective of this study was to determine the interactive effects of temperature and light intensity on CH4 and other relevant plant parameters in canola (Brassica napus L.). Plants were grown under two temperature regimes (22/18 °C and 28/24 °C, 16 h light/8 h dark) and two light intensities (300 and 600 μmol photons m−2 s−1) for 21 days after one week of growth under 22/18 °C (16 h light/8 h dark). In this study, higher temperature had little effects on CH4 emissions from plants, indicating the mitigating effects of higher light intensity. Higher light intensity, however, significantly decreased CH4, which was inversely related to plant dry mass. Higher light intensity decreased stem height, leaf area ratio, chlorophyll, nitrogen balance index, leaf moisture, methionine (Met) and ethylene (C2H4), but increased specific leaf mass, photochemical quenching, flavonoids, epicuticular wax, lysine and tyrosine. The results revealed that increased CH4 emissions from plants could be related to changes in plant physiological activities, which portrayed themselves in increased C2H4 evolution, and methylated amino acids, such as Met. We conclude that higher light intensity reduces Met and, in turn, CH4 and C2H4 emissions, but lower light intensity enhances CH4 formation through cleavage of methyl group of amino acids by reactive oxygen species, as previously suggested.

Physiological and Proteomic Characterization of the Elevated Temperature Effect on Sunflower (Helianthus annuus L.) Primary Leaves

This work examines the effect of increasing environmental temperatures, resulting from the ongoing global climate change, on the primary leaves of sunflower (Helianthus annuus L.). To do so, we examined physiological markers that are commonly used to monitor leaf development: specific leaf mass (SLM), leaf area, protein and photosynthetic pigment contents, net photosynthesis rate (PN), stomatal conductance (gs) transpiration and hydrogen peroxide (H2O2) content in the primary leaves of 42-day-old plants grown under standard diurnal and nocturnal temperatures (23 and 19°C, day/night), and under higher temperatures (33 and 29°C, day/night). Then, a proteomic approach was used to evaluate molecular alterations, at the protein level, between the two grown conditions. A total of 598387 raw spectra were obtained, yielding a total of 2343 identified protein sequences. Protein profiles were consistent with differences in protein expression between plants grown under the two temperature conditions. Interestingly, 619 (26.4%) of the identified proteins, mainly categorized in four functional groups (1-antioxidant, 2-stress and defense, 3-energy and metabolism-related, and 4-hormonal regulation proteins), exhibited increased expression in response to higher growth temperatures. These molecular differences detected in primary leaves at elevated temperatures could indicate a greater tolerance of sunflower plants to these stress conditions. This work provides a solid basis for elucidating their role and explaining the sunflower adaptive mechanisms to the increasing environmental temperature.

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.

Vehicular emissions effect on the physiology and health status of five tree species in a Bogotá, Colombia urban forest

ABSTRACT. Introduction: Thanks to filtration by foliage, urban trees have a crucial role in air depuration. However, the exposure to pollutants could reduce their health and physiological performance, mainly because of low access to light and clogging of stomata by particulate matter. Objective: The accumulation of particulate matter on leaves (PMAL) and physiological traits of five urban tree species (Croton bogotanus Cuatrec., Eugenia myrtifolia Sims., Ficus soatensis Dugand, Schinus mole L., and Sambucus nigra L.) were quantified in sixty points in Bogotá, with the aims to (1) build a model explaining the PMAL based on traffic variables, (2) establishing the effect of vehicle pollution on physiological and phytosanitary variables, and (3) to evaluate the susceptibility of seedlings and trees to vehicle pollution. Methods: The physiological parameters: photochemical efficiency, stomatal conductance, chlorophyll content, leaf area, and specific leaf mass were measured and correlated with phytosanitary condition, PMAL and traffic variables: number of lanes, vehicular flow and tree-to-avenue distance. Additionally, tree physiological responses were measured in control, residential streets (RS), low traffic avenues (LTA), and high traffic avenues (HTA), and these last were compared with physiology of seedlings planted by three months in HTA. Results: PMAL was strongly associated with physiological responses. Ficus soatensis and C. bogotanus were the species with the maximum and the minimum PMAL. The exposure to traffic increased the photochemical efficiency and specific leaf mass, which could be related to the enrichment of nitrogen and atmospheric CO2. The stomatal conductance followed a bell pattern of low gas exchange in control sites, high values in RS and LTA, and decreasing again in HTA, which suggests an optimization in CO2 fixation at intermediate levels of pollution and susceptibility to stomatal clogging by extreme vehicle emissions. The chlorophyll a/b ratio, leaf area, and specific leaf mass were significantly related to the severity of leaf symptoms, and S. molle was the species with the healthiest leaves in HTA. Seedlings were more susceptible to pollution than trees, and fruits size and seedlings growth were affected by vehicular pollution. Conclusions: Ficus soatensis optimizes particle filtration and C. bogotanus is ideal for planting in HTA, although only as saplings. By contrast, the fast-growing E. myrtifolia and S. nigra seedlings should not be planted in HTA because of susceptibility of pigment contents, leaf area, and stomatal conductance to pollutants. Finally, because of its persistent high stomatal conductance and its low leaf symptoms, S. molle is the species with the best adaptation to vehicle pollution. A complete analysis of interactions among traffic, physiology, and health will help to improve the urban forestry planning.

Photochemical performance and source-sink relationships in galls induced by Pseudophacopteron longicaudatum (Hemiptera) on leaves of Aspidosperma tomentosum (Apocynaceae)

The establishment of the galling insect generates a biotic stress that leads to tissue transformation. However, galls can maintain chlorophyll (Chl) and consequently photosynthesize. Herein, we evaluated the consequences of the biotic stress generated by the galling insect Pseudophacopteron longicaudatum on photosynthetic rate during the leaf galls development on Aspidosperma tomentosum. In addition, we quantified polysaccharides and water content in order to evaluate the capacity of gall tissues to drain photoassimilates. The non-galled leaves contained more Chl and carotenoids per gram of fresh mass. Galls had lower values of maximum PSII quantum yield, fluorescence decline ratio, and nonphotochemical quenching compared to non-galled tissue. These results showed a significant reduction of photosynthesis photochemistry in galled tissues although total soluble sugar did not differ between gall and non-galled leaves. Water-soluble polysaccharides, relative water content, and leaf specific mass were significantly higher in galls and increased through their development, suggesting a sink relationship.

Global response patterns of plant photosynthesis to nitrogen addition: A meta-analysis.

A mechanistic understanding of plant photosynthetic response is needed to reliably predict changes in terrestrial carbon (C) gain under conditions of chronically elevated atmospheric nitrogen (N) deposition. Here, using 2,683 observations from 240 journal articles, we conducted a global meta-analysis to reveal effects of N addition on 14 photosynthesis-related traits and affecting moderators. We found that across 320 terrestrial plant species, leaf N was enhanced comparably on mass basis (Nmass , +18.4%) and area basis (Narea , +14.3%), with no changes in specific leaf area or leaf mass per area. Total leaf area (TLA) was increased significantly, as indicated by the increases in total leaf biomass (+46.5%), leaf area per plant (+29.7%), and leaf area index (LAI, +24.4%). To a lesser extent than for TLA, N addition significantly enhanced leaf photosynthetic rate per area (Aarea , +12.6%), stomatal conductance (gs , +7.5%), and transpiration rate (E, +10.5%). The responses of Aarea were positively related with that of gs , with no changes in instantaneous water-use efficiency and only slight increases in long-term water-use efficiency (+2.5%) inferred from 13 C composition. The responses of traits depended on biological, experimental, and environmental moderators. As experimental duration and N load increased, the responses of LAI and Aarea diminished while that of E increased significantly. The observed patterns of increases in both TLA and E indicate that N deposition will increase the amount of water used by plants. Taken together, N deposition will enhance gross photosynthetic C gain of the terrestrial plants while increasing their water loss to the atmosphere, but the effects on C gain might diminish over time and that on plant water use would be amplified if N deposition persists.

Effect of integrated agronomic managements on leaf growth and endogenous hormone content of summer maize

<p indent=0mm>The leaves are the main place of photosynthesis directly related to the nutritional status, dry matter accumulation and yield formation of maize plants. The experiment was conducted using summer maize hybrid Zhengdan 958 with treatments of T1: local conventional cultivation practices; T2: based on T1, increasing planting density, delaying harvesting time, decreasing fertilizer application, and changing fertilization time; T3: based on T2, further increasing planting density, and further increasing fertilizer rate; T4: based on T3, decreasing planting density and the amount of fertilizer; and nitrogen treatments of N0, N1, N2, and N3, with 0, 129.0, 184.5, and <sc>300.0 kg N</sc> hm^-2, respectively. The contents of IAA, ZR, and GA₃ decreased and the content of ABA increased, resulting in the decreases of SPAD, leaf area index (LAI) and specific leaf mass, when nitrogen application was not enough. And the contents of IAA, ZR, and GA₃ increased, and ABA content decreased, and LAI, SPAD and dry matter accumulation per plant increased significantly with increasing nitrogen application. Integrated agronomic management practices could regulate the content of endogenous hormones in leaves. In T4 treatment, IAA, ZR, and GA₃ contents increased by 23.1%, 9.8%, and 14.7%, the ABA content decreased by 12.4%, resulting in a suitable LAI; SPAD and final dry matter accumulation per plant were by 4.2% and 12.6% higher, respectively, than those in T1 treatment. Integrated agronomic managements could coordinate endogenous hormone contents, increase leaf SPAD and specific leaf mass, and be beneficial to dry matter accumulation per plant under the condition of reducing nitrogen application combining with optimal agronomic managements, which might be one of the important reasons for increasing summer maize yield.

Propagation of Aloysia citriodora Palau Using Different Cutting Types under Light Intensity

Aims: The aim of this study was to evaluate the effect of types of cuttings and light intensity on cidró vegetative propagation.&#x0D; Place and Duration of Study: Medicinal Plants Garden, Federal University of Grande Dourados (UFGD), Dourados, state of Mato Grosso do Sul, Brazil, September to November 2016.&#x0D; Methodology: The experiment was carried out under two light conditions (shaded and full light), evaluating three types of cuttings (softwood, semi-hardwood and hardwood). Experimental design was a 2 x 3 factorial randomized complete block design (RCBD) with four replications.&#x0D; Results: Hardwood cuttings showed the highest survival rates (86% and 82%), regardless of light. Highest fresh weight (0.6062 g plant-1) and dry mass (0.2987 g plant-1) with a leaf of 44.57 cm2 were from hardwood cuttings, regardless of the light, while the longest root length were those of softwood cuttings under full light. Physiological indices varied as a function of light intensity, The highest values of leaf area ratio (46.11 cm2 g-1) and specific leaf mass (0.0037 g cm-2) occurred in cuttings under full light.&#x0D; Conclusion: The vegetative propagation of cidró can be carried out using the hardwood portion of the cutting branch, under full light.

UV-A light induces a robust and dwarfed phenotype in cucumber plants (Cucumis sativus L.) without affecting fruit yield

Solar ultraviolet (UV) light influences plant growth and metabolism. Whereas high doses of UV can be deleterious for plants, natural UV doses are important for morphogenesis in many plants species, including those used in horticulture. Greenhouses are widely used for horticultural production and common cladding materials strongly absorb UV. Thus, low amounts of UV may be limiting the optimal development in some plant species. Light supplementation using UV tubes can overcome UV deficiency. Here we study cucumber seedling production in the absence or presence of different UV wavelengths. UV-A- (315−400 nm) and UV-B- (280−315 nm) enriched light was used for exposure and parameters such as the maximum quantum yield of photosystem II, stem development (internode length and diameter, stem dry weight, stem weight per unit of stem length, and stem bending), root biomass, leaf biomass and specific leaf mass were measured. We found that UV-A supplementation resulted in shorter more compact and sturdy plants, properties that are positive from a horticultural perspective. In contrast, UV-B-enriched light led to even smaller plants that lacked the sturdy stem. There were no signs of decreased Fv/Fm under any of the treatments, nor statistically significant differences in fruit yield between the control plants and the UV-treated plants when grown to harvest. In particular, the differences in fruit yield between the controls and the UV-A-treated plants were negligible in all cases. Thus, supplementary UV-A light can be an interesting alternative to chemical growth regulators for production of sturdy horticultural plants.

Silicon sources for studies of rice plants in nutrient solutions

The objective of this work was to evaluate the effects of various Si sources currently used in studies of Si doses in nutrient solutions on dry matter yield and the accumulation of nutrients and Si in rice plants. Treatments of rice plants with three sources of Si (monossilicic acid, sodium metasilicate, potassium metasilicate) and a treatment without Si were allocated in a randomized block design with ten replications. After 39 days in the nutrient solution, the following traits were evaluated: leaf area, leaf specific mass, dry matter yield of roots and shoots, and levels of K, Na, and Si in leaves and roots. Si increased leaf area, leaf specific mass, and dry matter yield of shoots and roots regardless of the Si source. Levels of Si in leaves and roots were significantly higher in relation to the control treatment but no significant difference among Si sources was identified. It was also observed that K and Na were adequately balanced across the treatments. Thus, a cheaper and easier to obtain Si source, such as sodium metasilicate and potassium metasilicate, may be chosen to carry out studies of Si additions to nutrient solutions.

Minimum magnesium concentrations for photosynthetic efficiency in wheat and sunflower seedlings

Photosynthetic processes in the chloroplast depend on the abundance of magnesium (Mg) in relatively high amounts; hence chloroplasts might react more sensitive to Mg-deficiency than other physiological processes within other organelles. Most authors suggest a critical Mg concentration to be 1.5 mg g−1 DM for biomass and yield formation. However, it is not yet elucidated whether this value also applies to photosynthetic processes. The present study focused on the response of photosynthetic processes to different Mg tissue concentrations. Wheat (Triticum aestivum) and sunflower (Helianthus annuus) plants were grown hydroponically for 10 days with 8 different levels of Mg supply (1.0, 0.5, 0.25, 0.1, 0.075, 0.05, 0.025, 0.01 mM Mg). Specific leaf mass, SPAD values, assimilation rate, Fv/Fm, electron transport rate and photochemical and non-photochemical quenching parameters were determined on youngest mature leaves.Tissue Mg concentrations decreased with lowering Mg supply to lowest concentrations of 0.7 mg g−1 DM in wheat leaves, but photosynthetic capacity was not affected. In sunflower leaves, lowest Mg concentrations of 0.56 mg g−1 DM were achieved and a diminished photosynthetic capacity was observed. The study shows that a Mg tissue concentration of 1.5 mg g−1 DM did not induce a negative effect on the photosynthetic capacity of wheat and sunflower leaves under our experimental conditions and hence, the critical Mg concentration for photosynthetic processes might be lower than for biomass and yield formation.

Functional traits associated to photosynthetic plasticity of young Brazil nut (Bertholletia excelsa) plants

The Brazil nut shows the ability to establish itself in contrasting irradiance conditions. However, physiological strategies with respect to acclimatization to different irradiance still remain unknown. Here we investigated the leaf traits variations related to photosynthetic plasticity of Bertholletia excelsa. In this study, B. excelsa saplings were acclimated during 90 days (PPFD = 30 μmol m−2 s−1) and after the acclimatization, the saplings were subjected to two irradiance conditions: planting in full sun (100% PPFD) and planting in forests (1.5% PPFD). Following this, the specific leaf mass (SLM), gas exchange, maximum yield of photochemistry (FV/FM), chlorophyll and carbohydrate contents were evaluated. Net photosynthesis per unit area (Pn) of saplings in full sun was 2 times greater than in shade and photosynthesis in full sun was positively related to stomatal condutance (gs), dark respiration (Rd), carbohydrates and SLM. On the other hand, in shade, we observed an increase in the apparent quantum yield (α) and a reduction of SLM. Although B. excelsa reduced FV/FM by 30% in full sun, after 7 days it was able to recover from stress by the increase in irradiance. The traits that most contributed to explaining the photosynthetic plasticity were SLM (8.7%), FV/FM (7.7%), Rd (5.9%), gs (5.3%) and sugar (5.2%). Therefore, the fast recovery of photosynthesis during light stress and adjustments of morpho-functional traits in leaves to irradiance in B. excelsa are strong candidates to explain why this species establishes both in environments with low and high light availability.

Nitrogen effect on gas exchange characteristics, dry matter production and nitrate accumulation of Amaranthus cruentus L.

Among the mineral nutrients, nitrogen stands out as an essential constituent of amino acids, nucleic acids and proteins, as well as being part of the photosynthetic apparatus. The present study aimed to evaluate the responses of Amaranthus cruentus L. cv. BRS Alegria to nitrogen availability in terms of biomass production, photosynthetic characteristics, content of photosynthetic pigments, total nitrogen, ammonium and nitrate in the leaves. Plants of A. cruentus were cultivated in plastic pots filled with vermiculite and kept in a greenhouse under natural photo-periodic conditions. The plants were watered with 70% of full strength nitrogen-free Long Ashton solution, containing 1.97, 4.94 or 9.88 kg N ha−1 as ammonium nitrate, three times a week. Increased nitrogen availability resulted in higher shoot dry matter, specific leaf mass, total leaf nitrogen, chlorophyll and carotenoids as well as in higher photosynthetic rates. There was a positive correlation between photosynthesis and leaf nitrogen. Higher nitrogen availability resulted in greater stomatal conductance and transpiration, but the CO2 concentration in the sub-stomatal cavity was not significantly altered. In addition, an increase in ammonium and nitrate content of leaves was observed. The nitrate content reached 176, 193 and 288 mg kg−1 of dry matter in low, medium and high nitrogen supply, respectively. The data show that A. cruentus plants are sensitive to changes in nitrogen availability during the vegetative phase. The limitation of photosynthesis under conditions of low nitrogen supply cannot be fully explained by the reduction in stomatal conductance; non-stomatic limitations are also involved. In addition, the maximum nitrate content observed in leaves was far below the risk level for human health.

The long-term response of photosynthesis in walnut (Juglans regia L.) leaf to a leaf-to-fruit ratio

For clarifying the relationship between a leaf-to-fruit ratio (LFR) and photosynthesis, LFR manipulation was performed with Juglans regia cv. Xinxin2 in order to test the photosynthesis response to LFR in source leaves. Results showed that LFR with one and two leaves was positively correlated with net photosynthetic rate (PN), chlorophyll content, and specific leaf mass, implying extremely low LFR inhibited the leaf development. However, LFR with five leaves was negatively correlated with PN, positively correlated with starch, but not related to intercellular CO2 concentration, indicating the high LFR caused the nonstomatal limitation and feedback inhibition of photosynthetic production. No significant differences in PN between LFRs (with three and four leaves) probably indicated a balanced state of coordinated supply and demand between the source leaf and sink fruit. The above results indicated that the response of photosynthesis in the source leaves to LFR depends on the variation range of LFR.

Performance of Chia on Different Sowing Dates: Characteristics of Growth Rate, Leaf Area Index, Shoot Dry Matter Partitioning and Grain Yield

The objective of this study was to comparatively determine the characteristics of growth rate, leaf area index, shoot dry mass partitioning and grain yield of chia plants (Salvia hispanica L.) on different sowing dates. A field experiment was conducted in the crop year of 2016/2017 in five sowing dates (09/22/16, 10/28/16, 01/03/17, 02/08/17 and 03/24/17) with a randomized complete block design and four replicates. Plant growth was determined through field samplings to determine the dry matter mass and leaf area performed every 15 days. The following physiological indexes were calculated: relative growth rate, absolute growth rate, net assimilation rate, leaf area ratio, specific leaf area and leaf mass ratio. To weekly evaluate plant height, ten plants per plot were marked after emergence, and the final height was considered when plants reached physiological maturity. A useful area of 2.10 m&amp;sup2; per plot was collected for evaluating grain yield. The physiological indexes indicated that at earlier sowing dates there is a greater plant growth, either in shoot dry matter mass, height and leaf area index. The leaf area index of branches is progressively increased with plant development and contributes significantly to total leaf area index of chia plants in all studied sowing dates. The main stem represents between 60 and 70% of the shoot dry matter accumulated in the early sowing dates, and between 40 and 50% in late sowing. The best sowing date in terms of grain yield is 01/03/17.

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.

Leaf traits and photosynthetic characteristics of endangered Sinopodophyllum hexandrum (Royle) Ying under different light regimesin Southeastern Tibet Plateau

Sinopodophyllum hexandrum (Royle) Ying, a medicinal plant, has been endangered due to alpine habitat and overuse at Southeastern Tibet Plateau. This study aimed to examine the phenotypic traits and photosynthesis of S. hexandrum, including their relationship with main environmental factors, under low light (LL), moderate light (ML), and high light (HL) regimes. Low specific leaf mass was observed under LL, but the stomatal density and apparent quantum yield were the highest under this regime. The phenotypic traits, except for stomatal density and net photosynthetic rate, were the most notable under ML. The leaf area, stomatal density, apparent quantum yield, dark respiration, and stomatal conductance showed the smallest values under HL. Air temperature, photosynthetically active radiation, and air vapour pressure deficit significantly affected the stomatal characteristics and photosynthesis of S. hexandrum individuals. Our results suggested that a moderately shaded habitat could promote leaf development and the photosynthetic ability of S. hexandrum.