Functional relationship between photosynthetic leaf gas exchange in response to silicon application and water stress mitigation in sugarcane

BACKGROUND: Water stress is one of the serious abiotic stresses that negatively influences the growth, development and production of sugarcane in arid and semi-arid regions. However, silicon (Si) has been applied as an alleviation strategy subjected to environmental stresses. METHODS: In this experiment, Si was applied as soil irrigation in sugarcane plants to understand the mitigation effect of Si against harmful impact of water stress on photosynthetic leaf gas exchange. RESULTS: In the present study we primarily revealed the consequences of low soil moisture content, which affect overall plant performance of sugarcane significantly. Silicon application reduced the adverse effects of water stress by improving the net photosynthetic assimilation rate (Anet) 1.35-18.75%, stomatal conductance to water vapour (gs) 3.26-21.57% and rate of transpiration (E) 1.16-17.83%. The mathematical models developed from the proposed hypothesis explained the functional relationships between photosynthetic responses of Si application and water stress mitigation. CONCLUSIONS: Silicon application showed high ameliorative effects on photosynthetic responses of sugarcane to water stress and could be used for mitigating environmental stresses in other crops, too, in future.

Morphology, Leaf Gas Exchange and Quality of Pegaga (Centella asiatica) under Different Nitrogen Fertilization Rates

Aims: To investigate the physiological, leaf gas exchange and quality of Centella asiatica (pegaga) under different nitrogen fertilization rates. Study Design: Centella asiatica were exposed to four different nitrogen fertilization rates (0, 50, 100, 150 kg/ha) using urea (46% N) as nitrogen sources. The experiment was conducted in a randomized complete block (RCBD) design with three replications. Each treatment consisted of eight plants making the total of plants used in this study is 96 plants. Place and Duration of Study: Department of Biology, Faculty of Science, Universiti Putra Malaysia From May 2016-June 2016. Methodology: The growth parameters measured include total leaves numbers, leaf area, total chlorophyll content and total plant biomass. The carbon assimilation parameters were measured using LICOR 6400 XT Portable Photosynthesis System i.e net photosynthesis (A), Transpiration rate (E) and water use efficiency (WUE). Total phenolic and flavonoids contents from the leaves extracts were measured using Folin-Ciocalteu reagents. Results: The growth parameters such as leaves number, chlorophyll content, leaf area and total biomass were significantly influenced by nitrogen fertilization (P≤ 0.05), However, there were no significant difference observed between 50, 100 and 150 kg N/ha suggesting that 50 kg N/ha was the efficient rates to apply to enhance the growth of this plant. Meanwhile, the net photosynthesis (A) and water use efficiency (WUE) were enhanced with the increasing rate of nitrogen from 0>150 kgN/ha. The production of total phenolics and flavonoids was found to be highest under 100 kg/ha. The harvest index of total phenolics also showed the applications of 100 kg/ha gave the highest harvest index compared to the other nitrogen treatments. Conclusion: This study indicated growth and carbon assimilation parameters were enhanced under higher nitrogen fertilization and production of secondary metabolites was decreased with high rates of nitrogen. The recommended nitrogen fertilization for C. asiatica was at 100 kg N /ha, where it obtained the highest harvest index.

Physiological changes in sugarcane in function of air and ground application of fungicide for orange rust control / Alterações fisiológicas na cana-de-acúcar em função de aplicações aéreas e terrestre de fungicida no controle da ferrugem alaranjada

The application of fungicides in different operating conditions is a usual practice for maintaining the productive potential in sugarcane varieties considered susceptible to orange rust, however, the physiological effects provided by the different application methods are unknown. The objective of this study was to evaluate the photosynthetic responses (gas exchange and chlorophyll content) in the SP81-3250 sugarcane variety, in function of different operational conditions of the aerial and ground application of fungicide in the orange rust control. Two application of fungicides of the chemical groups Strobilurins and Triazoles were carried out in the experimental units in different treatments. In the aerial applications, two application rates (30 and 40 L ha-1) and three nozzle orientations (0º, 90º and 135º) and in the ground application was used 200 L ha-1 and flat fan spray nozzles with air induction (AI11004-VS). Gas exchange evaluations were performed with an IRGA and amount of chlorophyll a and b with a chlorophyll meter. Data were analyzed using Student's t-test for independent samples, at 0.05 significance. The aerial application provided better photosynthetic responses and chlorophyll a and b contents in leaf limb compared to ground application. Significant differences were detected in gas exchange and chlorophyll content between application rates and angulation of the spray nozzles in the boom. Fungicide applications provided increments of more than 19 t ha-1 compared to the control, depending on the spraying technique employed. Aerial application with 30 L ha-1 and 0° of deflection is a viable option to provide safer applications as a function of the larger droplet size.

A aplicação de fungicidas em diferentes condições operacionais é uma prática usual para manter o potencial genético em variedades de cana-de-açúcar consideradas susceptíveis à ferrugem laranja, porém os efeitos fisiológicos proporcionados pelos diferentes métodos de aplicação são desconhecidos. O objetivo deste estudo foi avaliar as respostas fotossintéticas (troca gasosa e teor de clorofila) na variedade de cana-de-açúcar SP81-3250, em função de diferentes condições operacionais de aplicação aérea e terrestre de fungicida no controle da ferrugem alaranjada. Duas aplicações de fungicidas dos grupos químicos Estrobilurinas e Triazóis foram realizadas nas unidades experimentais em diferentes tratamentos. Nas aplicações aéreas, foram utilizadas duas taxas de aplicação (30 e 40 L ha-1) e três orientações do ângulo dos bicos (0º, 90º e 135º) e na aplicação terrestre 200 L ha-1 e pontas de pulverização de jato plano com indução de ar (AI11004 -VS). As avaliações de trocas gasosas foram realizadas com analisador de gás IRGA e a quantidade de clorofila a e b com um medidor de clorofila. Os dados foram analisados utilizando o teste t de Student para amostras independentes, com um valor de 0,05 de significancia. A aplicação aérea proporcionou melhores respostas fotossintéticas e os teores de clorofila a e b no membro foliar em comparação com a aplicação terrestre. Foram detectadas diferenças significativas na troca gasosa e no teor de clorofila entre as taxas de aplicação e a angulação dos bicos de pulverização na barra. As aplicações de fungicidas proporcionaram incrementos de mais de 19 t ha-1 em relação ao tratamento controle, dependendo da técnica de pulverização empregada. A aplicação aérea com 30 L ha-1 e 0° de deflexão é uma opção viável para proporcionar aplicações mais seguras em função do maior tamanho das gotas.

Effect of Nitrogen Rates on Growth and Quality of Water Spinach (Ipomea aquatica)

Aims: The study was conducted to investigate the impact of nitrogen fertilization on growth, leaf gas exchange and bio-metabolite accumulation in Ipomea aquatica. Treatment and Experimental Design: Ipomea aquatica plants were exposed to four different rates of nitrogen (0, 30, 60 and 90 N kg/ha) using Urea (46% N) as a nitrogen source. The experiment was laid out in Complete Randomize Design (CRD). Place and Duration of Study: Department of Biology, Faculty of Science, Universiti Putra Malaysia between September to November 2016. Methodology: Four nitrogen rates were applied (0, 30, 60 and 90 N Kg/ha) using Urea as a nitrogen source. The growth data collections were conducted once a week after the application of the treatments for the plant growth parameters. The total chlorophyll content in the leaves was measured using a Soil Plant Analytical Device (SPAD-502) chlorophyll meter. The leaf gas exchange was determined using a LI-6400XT portable photosynthesis system. Total phenolics and flavonoid were determined using Folin-Ciocalteu reagent. Results: It was found that the highest measurements of growth parameters namely plant height, leaf numbers, branches numbers, total biomass and chlorophyll content were observed at 90 kg N/ha and the lowest at 0 kg N/ha. As for the leaf gas exchange, the positive effect of nitrogen fertilization on kangkung was shown by the increased in photosynthesis rate (A) and stomatal conductance (gs) where the highest measurement recorded at 90 kg N/ha, and the lowest at 0 kg N/ha. However, the water use efficiency (WUE) decreased as the nitrogen rates increased. At lower rates of nitrogen fertilization (30 kg N/ha) produced the highest production of secondary metabolites, where the total phenolics and flavonoids production were enhanced compared to other nitrogen treatments. Conclusion: In conclusion, as the nitrogen rates increased, the growth and leaf gas exchange properties was enhanced however the production of secondary metabolites was decreased in I. aquatica.

Growth, Leaf Gas Exchange and Secondary Metabolites of Orthosiphon stamineus as Affected by Multiwall Carbon Nanotubes Application

Aims: This study was conducted to study the growth, leaf gas exchange and secondary metabolites of Orthosiphon stamineus as affected by Multiwalled carbon nanotubes application (MWCNT). Study Design: Orthosiphon stamineus were exposed to four different multi-walled carbon nanotubes (MWCNTs) concentration (0, 700, 1400 and 2100 mg L-1). The experiment was organized in a randomized complete block (RCBD) design with three replications. Each experimental unit consisted of twelve plants, and there were a total of 144 plants used in the experiment. Place and Duration of Study: Department of Biology, Faculty of Science Universiti Putra Malaysia between November 2016 to March 2017. Methodology: Each plant was watered with 50 mL of MWCNTs solution in week 2 and 9. The leaves number were counted manually and the total plant biomass was taken by calculating the dry weight of root, stem, and leaf per seedling The total chlorophyll content in the leaves was measured using a SPAD chlorophyll meter. The leaf gas exchange was determined using LI-6400XT portable photosynthesis system. Total phenolics and flavonoid were determined using Folin-Ciocalteu reagent. Results: It was found that application of MWCNTs would reduce the growth characteristics of this plant that was shown by decreased leaf numbers, total biomass and total chlorophyll content (TCC). As MWCNTs concentration increases from 0 > 2100 mg L-1, the leaf gas exchange parameter also shows reduced patterns. Generally, as the rate of MWCNTs increased from 700 > 2100 mg L-1 MWCNTs reduce the net photosynthesis (A), stomatal conductance (gs), transpiration rate (E) and increased the plant water use efficiency. The production of the secondary metabolites was directly dependable on MWCNTs concentration. As the rate was enhanced from 0 > 700 > 1400 > 2100 mg L-1 the production of total phenolics and flavonoids was enhanced. Conclusion: The current study revealed that the high application of MWCNTs concentration reduce the growth rate of O. stamineus, leaf gas exchange and simultaneously increase the production of secondary metabolites.

Drought induced changes in growth, leaf gas exchange and biomass production in Albizia lebbeck and Cassia siamea seedlings.

Diurnal trends in net photosynthesis rate (PN ), stomatal conductance (gs ), water use efficiency (WUE) and biomass were compared in six-month-old seedlings of Albizia lebbeck and Cassia siamea, under different levels of drought stress. The potted plants were subjected to four varying drought treatment by withholding watering for 7 (D1), 14 (D2) and 25 (D3) days. The fourth group (C) was watered daily and treated as unstressed (control). Species differed significantly (p<0.001) in their physiological performance under varying stress conditions. Higher PN of 11.6 ± 0.05 in control followed by 4.35 ± 0.4 in D1 and 2.83 ± 0.18 @mol m-2 s-1 in D2 was observed in A. lebbeck. A significant (p<0.001) reduction in PN was observed in C. siamea ( C 7.65 ± 0.5 @mol m-2 s-1, D1, 2.56 ± 0.33 @mol m-2 s-1 and D2, 1.4 ± 0.01 @mol m-2 s-1 ) at 9 hr. A positive correlation was seen between PN and gs (A. lebbeck, r2= 0.84; C. siamea, r2= 0.82). Higher WUE was observed in C. siamea (D2, 7.1± 0.18 @mol m-2 s-1; D3, 8.39 ± 0.11 @mol m-2 s-1) than A. lebbeck, (control, 7.58 ± 0.3 @mol m-2 s-1 and D3, 8.12 ± 0.15 @mol m-2 s-1). The chlorophyll and relative water content (RWC) was more in A. lebbeck than C. siamea. Maximum biomass was produced by A. lebbeck than C. siamea. From the study, one could conclude that A. lebbeck is better than C. siamea in adopting suitable resource management strategy and be best suited for the plantation programs in the semi-arid dry lands.

Evidence of higher photosynthetic plasticity in the early successional Guazuma ulmifolia Lam. compared to the late successional Hymenaea courbaril L. grown in contrasting light environments / Evidências de maior plasticidade fotossintética na pioneira Guazuma ulmifolia Lam. comparada à secundária Hymenaea courbaril L. crescidas em ambientes luminosos contrastantes

The present study investigated changes in photosynthetic characteristics of Guazuma ulmifolia Lam. (early successional species) and Hymenaea courbaril L. (late successional species) grown in contrasting light conditions as a way of assessing photosynthetic plasticity. Early successional species typically inhabit gap environments being exposed to variability in multiple resources, hence it is expected that these species would show higher photosynthetic plasticity than late successional ones. In order to test this hypothesis, light and CO2 response curves and chlorophyll content (Chl) were measured in plants grown in high and low light environments. G. ulmifolia presented the highest amounts of both Chl a and b, especially in the low light, and both species presented higher Chl a than b in both light conditions. The Chl a/b ratio was higher in high light leaves of both species and greater in G. ulmifolia. Taken together, these results evidence the acclimation potential of both species, reflecting the capacity to modulate light harvesting complexes according to the light environment. However, G. ulmifolia showed evidence of higher photosynthetic plasticity, as indicated by the greater amplitude of variation on photosynthetic characteristics between environments shown by more significant shade adjusted parameters (SAC) and principal component analysis (PCA). Thus, the results obtained were coherent with the hypothesis that the early successional species G. ulmifolia exhibits higher photosynthetic plasticity than the late successional species H. courbaril.

O presente estudo investigou mudanças nas características fotossintéticas de Guazuma ulmifolia Lam. (pioneira) e Hymenaea courbaril L. (secundária) crescidas sob condições luminosas contrastantes, como uma maneira de acessar a plasticidade fotossintética das espécies. Espécies pioneiras geralmente habitam ambientes de clareira, expostas a uma ampla variação em múltiplos recursos, o que indica que essas espécies podem apresentar maior plasticidade fotossintética do que espécies secundárias. A fim de testar essa hipótese, foram feitas curvas de resposta à luz e ao CO2 e medidas do conteúdo de clorofila (Chl) em plantas crescidas em ambientes com alta e baixa luminosidade. G. ulmifolia apresentou os maiores teores de Chl a e b, principalmente em baixa luminosidade, e ambas as espécies apresentaram maior conteúdo de clorofila a do que b em ambas as condições luminosas. A razão Chl a/b foi maior em folhas de sol em ambas as espécies e foi mais elevada em G. ulmifolia. Conjuntamente, esses resultados evidenciam um potencial de aclimatação em ambas as espécies, indicando a capacidade de modular os complexos antena de acordo com o ambiente luminoso. Contudo, G. ulmifolia mostrou evidências de maior plasticidade fotossintética, conforme indicado pela maior amplitude de variação nas características fotossintéticas entre ambientes, maior número de parâmetros significativamente justados à sombra (SAC) e pela análise de componentes principais (PCA). Assim, os resultados obtidos foram coerentes com a hipótese de que a espécie pioneira G. ulmifolia apresenta maior plasticidade fotossintética do que a secundária H. courbaril.

Evidence of higher photosynthetic plasticity in the early successional Guazuma ulmifolia Lam. compared to the late successional Hymenaea courbaril L. grown in contrasting light environments

The present study investigated changes in photosynthetic characteristics of Guazuma ulmifolia Lam. (early successional species) and Hymenaea courbaril L. (late successional species) grown in contrasting light conditions as a way of assessing photosynthetic plasticity. Early successional species typically inhabit gap environments being exposed to variability in multiple resources, hence it is expected that these species would show higher photosynthetic plasticity than late successional ones. In order to test this hypothesis, light and CO2 response curves and chlorophyll content (Chl) were measured in plants grown in high and low light environments. G. ulmifolia presented the highest amounts of both Chl a and b, especially in the low light, and both species presented higher Chl a than b in both light conditions. The Chl a/b ratio was higher in high light leaves of both species and greater in G. ulmifolia. Taken together, these results evidence the acclimation potential of both species, reflecting the capacity to modulate light harvesting complexes according to the light environment. However, G. ulmifolia showed evidence of higher photosynthetic plasticity, as indicated by the greater amplitude of variation on photosynthetic characteristics between environments shown by more significant shade adjusted parameters (SAC) and principal component analysis (PCA). Thus, the results obtained were coherent with the hypothesis that the early successional species G. ulmifolia exhibits higher photosynthetic plasticity than the late successional species H. courbaril.

O presente estudo investigou mudanças nas características fotossintéticas de Guazuma ulmifolia Lam. (pioneira) e Hymenaea courbaril L. (secundária) crescidas sob condições luminosas contrastantes, como uma maneira de acessar a plasticidade fotossintética das espécies. Espécies pioneiras geralmente habitam ambientes de clareira, expostas a uma ampla variação em múltiplos recursos, o que indica que essas espécies podem apresentar maior plasticidade fotossintética do que espécies secundárias. A fim de testar essa hipótese, foram feitas curvas de resposta à luz e ao CO2 e medidas do conteúdo de clorofila (Chl) em plantas crescidas em ambientes com alta e baixa luminosidade. G. ulmifolia apresentou os maiores teores de Chl a e b, principalmente em baixa luminosidade, e ambas as espécies apresentaram maior conteúdo de clorofila a do que b em ambas as condições luminosas. A razão Chl a/b foi maior em folhas de sol em ambas as espécies e foi mais elevada em G. ulmifolia. Conjuntamente, esses resultados evidenciam um potencial de aclimatação em ambas as espécies, indicando a capacidade de modular os complexos antena de acordo com o ambiente luminoso. Contudo, G. ulmifolia mostrou evidências de maior plasticidade fotossintética, conforme indicado pela maior amplitude de variação nas características fotossintéticas entre ambientes, maior número de parâmetros significativamente justados à sombra (SAC) e pela análise de componentes principais (PCA). Assim, os resultados obtidos foram coerentes com a hipótese de que a espécie pioneira G. ulmifolia apresenta maior plasticidade fotossintética do que a secundária H. courbaril.

Diurnal and seasonal carbon balance of four tropical tree species differing in successional status / Balanço de carbono diurno e sazonal de quatro espécies tropicais arbóreas de diferentes grupos sucessionais

This study addressed some questions about how a suitable leaf carbon balance can be attained for different functional groups of tropical tree species under contrasting forest light environments. The study was carried out in a fragment of semi-deciduous seasonal forest in Narandiba county, São Paulo Estate, Brazil. 10-month-old seedlings of four tropical tree species, Bauhinia forficata Link (Caesalpinioideae) and Guazuma ulmifolia Lam. (Sterculiaceae) as light-demanding pioneer species, and Hymenaea courbaril L. (Caesalpinioideae) and Esenbeckia leiocarpa Engl. (Rutaceae) as late successional species, were grown under gap and understorey conditions. Diurnal courses of net photosynthesis (Pn) and transpiration were recorded with an open system portable infrared gas analyzer in two different seasons. Dark respiration and photorespiration were also evaluated in the same leaves used for Pn measurements after dark adaptation. Our results showed that diurnal-integrated dark respiration (Rdi) of late successional species were similar to pioneer species. On the other hand, photorespiration rates were often higher in pioneer than in late successional species in the gap. However, the relative contribution of these parameters to leaf carbon balance was similar in all species in both environmental conditions. Considering diurnal-integrated values, gross photosynthesis (Pgi) was dramatically higher in gap than in understorey, regardless of species. In both evaluated months, there were no differences among species of different functional groups under shade conditions. The same was observed in May (dry season) under gap conditions. In such light environment, pioneers were distinguished from late successional species in November (wet season), showing that ecophysiological performance can have a straightforward relation to seasonality.

Este estudo considerou algumas questões sobre como um adequado balanço de carbono foliar pode ser obtido por diferentes grupos funcionais de espécies tropicais arbóreas sob contrastantes ambientes luminosos em uma floresta. O estudo foi realizado em um fragmento de floresta estacional semidecidual localizada no município de Narandiba, Estado de São Paulo. Plântulas com dez meses de idade de quatro espécies, Bauhinia forficata Link (Caesalpinioideae) e Guazuma ulmifolia Lam. (Sterculiaceae) como espécies pioneiras, e Hymenaea courbaril L. (Caesalpinioideae) e Esenbeckia leiocarpa Engl. (Rutaceae) como espécies secundárias, cresceram em um ambiente de clareira e um de sub-bosque durante nove meses. Cursos diários da fotossíntese líquida (Pn) e transpiração foram medidos com um medidor portátil de trocas gasosas por infravermelho nas estações seca e chuvosa. A respiração no escuro (Rd) e a fotorrespiração (Pr) foram também avaliadas nas mesmas folhas utilizadas para as medidas de Pn após um período de adaptação ao escuro. Nossos resultados mostraram que a respiração integrada ao longo do dia foi similar entre as espécies dos dois grupos sucessionais. Por outro lado, a fotorrespiração das espécies pioneiras foi freqüentemente maior do que nas espécies secundárias em condições de clareira. Todavia, a contribuição relativa de Pr no balanço de carbono nas folhas foi similar em todas as espécies em ambos os ambientes. Independentemente da espécie, a fotossíntese bruta, considerando os valores integrados ao longo do dia, foi significativamente maior na clareira que no sub-bosque. Nas duas épocas avaliadas, não foram observadas diferenças significativas em nenhum dos parâmetros avaliados entre as espécies crescidas no ambiente de sub-bosque. O mesmo foi observado no mês de maio sob condições de clareira. No mês de novembro, as espécies pioneiras apresentaram uma performance ecofisiológica significativamente distinta das espécies secundárias no ...

Fotossíntese, condutância estomática e potencial hídrico foliar em árvores jovens de andiroba (Carapa guianensis) / Photosynthesis, stomatal conductance and leaf water potential in crabwood (Carapa guianensis)

O potencial hídrico da folha é um dos fatores mais importantes que afetam o funcionamento dos estômatos. O objetivo deste trabalho foi avaliar o efeito da variação diurna na irradiância e déficit de pressão de vapor (DPV) na fotossíntese (A), condutância estomática (g s) e potencial hídrico da folha (psi) em Carapa guianensis (Aubl.). Os dados foram coletados de 07:00 às 17:00 h. A taxa fotossintética atingiu um valor máximo (2,5 æmol m-2 s-1) às 10:00 h, depois declinou até atingir um mínimo de 1 æmolm-2 s-1 às 16:00 h. A condutância estomática oscilou durante o dia, de 0,04 molm-2s-1 (ao meio dia) para 0,02 molm-2s- 1 no final da tarde. O potencial hídrico da folha foi máximo nas primeiras horas do dia (-0,3 MPa) e mínimo (-0,75 MPa) no meio da tarde (14:30 a 15:00 h). Após ter alcançado um mínimo, o psi aumentou até -0,64 MPa no fim da tarde. A taxa fotossintética aumentou linearmente em função do g s (P < 0,01). Também houve uma relação positiva entre psi e g s (P < 0,01). A taxa fotossintética declinou durante o dia após ter alcançado um pico no início da manhã, demonstrando que os fatores ambientais que afetam o psi têm efeito significativo na assimilação do carbono de C. guianensis.

Leaf water potential is one of the most important factors affecting stomatal functioning. The aim of this study was to assess the effect of variation in diurnal irradiance and vapour pressure deficit on photosynthesis (A), stomatal conductance (g s) and leaf water potential (psi) in Carapa guianensis (Aubl.). Data were collected from 07:00 to 17:00 h. Photosynthetic rates reached a maximum (2.5 æmol m-2 s-1) at 10:00 h, thereafter declined to a minimum of 1 æmol m-2 s-1 at 16:00 h. Stomatal conductance oscillated during the day, from 0.04 mol m-2 s-1 (at midday) to 0.02.mol.m-2.s-1 at the end of the afternoon. Leaf water potential was higher early in the morning (-0.3 MPa) and lower (-0.75 MPa) at mid-afternoon (14:30 -15:00 h). After reaching a minimum, psi increased up to -0.64 MPa at sunset. Photosynthetic rates increased linearly as a function of g s (P < 0.01). Also there was a positive relationship between psi and g s (P< 0.01). Photosynthetic rates declined during the day after reaching a peak early in the morning, which makes clear that environmental factors that influence psi greatly affect carbon assimilation of C. guianensis.