Temporal dynamics of stomatal conductance of plants under water deficit: can homeostasis be improved by more complex dynamics?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Drought tolerance is associated with rooting depth and stomatal control of water use in clones of Coffea canephora

center dot Background and Aims Drought is a major environmental constraint affecting growth and production of Coffea canephora. Selection of C. canephora clones has been largely empirical as little is known about how clones respond physiologically to drought. Using clones previously shown to differ in drought tolerance, this study aimed to identify the extent of variation of water use and the mechanisms responsible, particularly those associated morphological traits.center dot Methods Clones (14 and 120, drought-tolerant; 46 and 109A, drought-sensitive, based on their abilities to yield under drought) were grown in 120-L pots until they were 12-months old, when an irrigation and a drought treatment were applied; plants were droughted until the pressure potential (Psi(x)) before dawn (pre-dawn) reached -3.0 MPa. Throughout the drought period, Psi(x) and stomatal conductance (g(s)) were measured. At the end of the experiment, carbon isotope ratio and parameters from pressure-volume curves were estimated. Morphological traits were also assessed.center dot Key Results and Conclusions With irrigation, plant hydraulic conductance (K-L), midday Psi(x) and total biomass were all greater in clones 109A and 120 than in the other clones. Root mass to leaf area ratio was larger in clone 109A than in the others, whereas rooting depth was greater in drought-tolerant than in drought-sensitive clones. Predawn Psi(x) of -3.0 MPa was reached fastest by 109A, followed progressively by clones 46, 120 and 14. Decreases in g(s) with declining Psi(x), or increasing evaporative demand, were similar for clones 14, 46, and 120, but lower in 109A. Carbon isotope ratio increased under drought; however, it was lower in 109A than in other clones. For all clones, Psi(x), g(s) and KL recovered rapidly following re-watering. Differences in root depth, KL and stomatal control of water use, but not osmotic or elastic adjustments, largely explained the differences in relative tolerance to drought stress of clones 14 and 120 compared with clones 46 and 109A.

Respostas fisiológicas de diferentes clones de eucalipto sob diferentes regimes de irrigação

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Physiological dose response of coffee (Coffea arabica L.) plants to glyphosate depends on growth stage

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Deficiência hídrica agrava os sintomas fisiológicos da clorose variegada dos citros em laranjeira 'Natal'

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Respostas de plantas de Eleusine indica sob diferentes condições hídricas a herbicidas inibidores da ACCase

Objetivou-se neste estudo avaliar a eficiência de controle de herbicidas inibidores da ACCase aplicados em pós-emergência em plantas de Eleusine indica submetidas a diferentes teores de água no solo. Os experimentos foram conduzidos em casa de vegetação, com a aplicação de três diferentes herbicidas (fluazifop-p-butil, haloxyfop-methyl e sethoxydim + óleo mineral Assist); o delineamento experimental utilizado para cada herbicida foi inteiramente casualizado, com quatro repetições, constituído de um fatorial 3 x 4, sendo a combinação de três manejos hídricos (-0,03, -0,07 e -1,5 MPa) e quatro doses desses produtos (100, 50, 25 e 0% da dose recomendada). Os parâmetros fisiológicos avaliados foram: taxa fotossintética, condutância estomática, transpiração, temperatura da folha e matéria seca das plantas. As avaliações visuais de fitotoxicidade foram realizadas aos 14 dias após a aplicação. Os manejos hídricos aplicados não influenciaram o controle das plantas nos tratamentos testados, com exceção do herbicida sethoxydim, que teve sua eficiência hídrica prejudicada quando da deficiência hídrica nas aplicações das doses fracionadas. A taxa fotossintética, a transpiração e a condutância estomática foram maiores em plantas submetidas ao manejo hídrico de 13%, as quais apresentaram as menores temperaturas foliares em relação à temperatura ambiente.

Influência da enxertia nas trocas gasosas de dois híbridos de berinjela cultivados em ambiente protegido

Compararam-se os efeitos da enxertia nas trocas gasosas de dois híbridos de berinjela em pé franco e enxertado. Conduziu-se um ensaio em ambiente protegido, na FCA/UNESP, em estrutura simples, tipo arco com 7 m de largura, 40 m de comprimento e 3 m de pé direito, cobertos por filme plástico de 100 micrometros. Foram utilizados os híbridos de berinjela Nápoli e Kokuyo, enxertados em porta-enxerto específico (híbrido Taibyo VF) para esta espécie. O delineamento experimental utilizado foi inteiramente casualizado, com quatro tratamentos (Nápoli pé franco, Nápoli enxertada, Kokuyo pé franco e Kokuyo enxertada) com dez repetições. A assimilação líquida de CO2 (A), transpiração (E), condutância estomática (g s) e eficiência no uso de água (EUA), obtida pela relação (A/E), foram determinadas às 09:00; 12:00; 14:00 e 16:00 horas em um dia sem nebulosidade com fluxo de fótons fotossinteticamente ativos (FFFA) de 937±126 mmol m-2 s-1, com um sistema fechado portátil de fotossíntese, IRGA, modelo LI-6200 (LI-COR). Observou-se que as plantas do híbrido Kokuyo apresentaram maiores valores para as variáveis A, E, g s e EUA que o híbrido Nápoli. A enxertia não afetou a capacidade fotossintética dos híbridos, porém, esta resultou em menores valores de E e g s nos dois híbridos, levando à maior EUA, efeito este que na prática pode resultar em menor demanda de água pelas plantas.

Effect of water stress on herbicide efficiency applied to Urochloa decumbens

M.R. Rocha-Pereira, A.E. Klar, D. Martins, G.S. Ferreira de Souza, and J. Villalba. 2012. Effect of water stress on herbicide efficiency applied to Urochloa decumbens. Cien. Inv. Agr. 39(1): 211-220. This project aimed to measure the control efficiency of Acctil Coenzime A Carboxilase (ACCase)-inhibiting herbicides post-emergence applied to Urochloa decumbens (Stapf) R.D. Webster under different soil water contents. The experiment was conducted in a greenhouse at the Department of Plant Production, Faculty of Agronomic Sciences, UNESP, Botucatu, Silo Paulo. The experimental design was a completely randomized design with four replications, consisting of a 9 x 4 factorial, combined with three water management systems (-0.03, -0.07 and -1.5 MPa) and three herbicides (fluazifop-p-butyl, haloxyfop-methyl and sethoxydim + oil using four doses (100, 50, 25 and 0% of the recommended dose). Herbicide applications were conducted at two vegetative stages for all species: a 4-6 leaf stage and a 2-3 tiller stage. The physiological parameters evaluated were as follows: photosynthetic rate, stomatal conductance, transpiration, leaf temperature and plant dry matter. The visual assessments of phytotoxicity were performed 28 days after herbicide application. The control efficiency was lower in plants grown under soil water potential conditions of -1.5 MPa, regardless of the herbicide used during the two application stages; however, none reached 100% control. Fractionation of the recommended herbicide doses reduced effectiveness, with the exception of the 50%-dose application of sethoxydim and fluazifop-p-butyl herbicides, which were also effective in the 4-6 leaf plant control under normal water conditions.

Efeito da deriva de Glyphosate sobre algumas características fisiológicas em plantas de eucalipto

This work aims to evaluate the effects of a simulated drift of glyphosate at different doses on some physiological characteristics of Eucalyptus grandis. A completely randomized design with five replications was used, where each pot contained an eucalyptus plant and was considered as one repetition. The plants received doses of glyphosate corresponding to 0, 30, 60, 90 and 120g.ha(-1), in the Scout (R) commercial formulation: The application was performed in three forms: leaves, stem and whole plant (leaf + stem). For foliar application, the stem was covered with plastic tape to avoid being hit by the solution, and leaves with a plastic bag when the stem was spayed. The application was performed by means of a steady spray gun equipped with four XR 11002 tips, with a pressure of 200Kpa and a volume of 2001 ha(-1). Stomatal conductance, transpiration and leaf temperature were measured at 7 days after application (DAA). The eucalypt plants receiving applications in leaves and whole plant showed, at the highest glyphosate dosis (120g.ha(-1)), a transpiration reduced by 22% and an 18% increase of stomatal resistance at 7 DAA. The lowest dose (30g-ha(-1)) applied to the whole plant caused a transpiration stimulation of 18%, and a leaf to air difference in temperature of -1.66 degrees C, while the difference between the highest and lowest dose used was 3.5 degrees C.

Gas exchange rates, plant height, yield components, and productivity of upland rice as affected by plant regulators

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of nitrogen supply on growth and photosynthesis of sunflower plants grown in the greenhouse

The effects of nitrogen availability on growth and photosynthesis were followed in plants of sunflower (Helianthus annuus L., var. CATISSOL-01) grown in the greenhouse under natural photoperiod. The sunflower plants were grown in vermiculite under two contrasting nitrogen supply, with nitrogen supplied as ammonium nitrate. Higher nitrogen concentration resulted in higher shoot dry matter production per plant and the effect was apparent from 29 days after sowing (DAS). The difference in dry matter production was mainly attributed to the effect of nitrogen on leaf production and on individual leaf dry matter. The specific leaf weight (SLW) was not affected by the nitrogen supply. The photosynthetic CO2 assimilation (A) of the target leaves was remarkably improved by high nitrogen nutrition. However, irrespective of nitrogen supply, the decline in photosynthetic CO2 assimilation occurred before the end of leaf growth. Although nitrogen did not change significantly stomatal conductance (gs), high-N grown plants had lower intercellular CO2 concentration (C-i) when compared with low-N grown plants. Transpiration rate (E) was increased in high-N grown plants only at the beginning of leaf growth. However, this not resulted in lower intrinsic water use efficiency (WUE). (C) 2004 Elsevier B.V.. All rights reserved.

Gas exchange rates at different vapor pressure deficits and water relations of 'Pera' sweet orange plants with citrus variegated chlorosis (CVC)

Net photosynthesis (A) and transpiration rates (E), stomatal conductance (g), water use efficiency (WUE), intrinsic water use efficiency (IWUE) and internal leaf CO2 concentration (C) in response to different vapor pressure deficit (1.2 and 2.5 kPa) were investigated in 'Pera' sweet orange plants affected by citrus variegated chlorosis (CVC), a disease caused by Xylella fastidiosa. All plants were well watered and leaf water potential (Pw) was also measured by the psychrometric technique. Results showed that healthy plants responded to higher vapor pressure deficit (VPD), lowering its net photosynthesis and transpiration rates, and stomatal conductance. However, diseased plants presented no clear response to VPD, showing lower A, E and g for both VPDs studied and very similar values to these variables in healthy plants at the highest VPD. Internal leaf CO2 concentration also decreased for healthy plants when under the highest VPD, and surprisingly, the same pattern of response was found in plants with CVC. These results, the lower Psi(w) and higher WUE values for diseased plants, indicated that this disease may cause stomatal dysfunction and affect the water resistance through xylem vessels, which ultimately may play some role in photosynthetic metabolism. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Crescimento e índices de troca gasosa em plantas de pepino irrigadas com água enriquecida com CO2

Avaliou-se o efeito do enriquecimento da água de irrigação com CO2 sobre índices fisiológicos de desenvolvimento e troca gasosa de folhas de plantas de pepino do tipo japonês, cultivados em ambiente protegido. Os experimentos realizados em duas épocas do ano foram instalados em delineamento experimental de blocos ao acaso com 4 tratamentos e 5 repetições. Os tratamentos foram constituídos pelos híbridos Hokuho e Tsuyataro, irrigados com água comum ou enriquecida com CO2, em uma concentração de 1 no primeiro e 0,25 no segundo experimento. A produção de massa de material seco e área foliar adotaram tendência exponencial, não sendo possível observar o início da diminuição da taxa de produção de massa do material seco aos 63 dias após transplante (DAT). A taxa de crescimento da comunidade e taxa de crescimento relativa do híbrido Hokuho irrigado com água comum foi diferente do irrigado com água enriquecida com CO2, no entanto, no híbrido Tsuyataro foram semelhantes. A taxa de assimilação líquida atingiu a máxima pendente na fase de crescimento vegetativo e floração, e foi reduzida drasticamente após os 20 DAT no híbrido Hokuho, e após os 35 DAT no híbrido Tsuyataro. A razão de área foliar diminuiu ligeiramente nos dois híbridos com o desenvolvimento do cultivo. No início observaram-se diferenças entre irrigação com água comum e enriquecida com CO2, porém após 20 DAT não se apreciaram mais diferenças. Quanto a troca gasosa, a taxa assimilatória líquida de CO2 e de transpiração, conductância estomática e eficiência no uso da água foram semelhantes entre plantas irrigadas com água comum e enriquecida com CO2 durante o primeiro semestre. Já no segundo semestre, maiores valores foram registrados pelas plantas irrigadas com água enriquecida.

Differential responses between mature and young leaves of sunflower plants to oxidative stress caused by water deficit

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ultraviolet-B and water stress effects on growth, gas exchange and oxidative stress in sunflower plants

The effects and interaction of drought and UV-B radiation were studied in sunflower plants (Helianthus annuus L. var. Catissol-01), growing in a greenhouse under natural photoperiod conditions. The plants received approximately 1.7 W m(-2) (controls) or 8.6 W m(-2) (+UV-B) of UV-B radiation for 7 h per day. The UV-B and water stress treatments started 18 days after sowing. After a period of 12 days of stress, half of the water-stressed plants (including both UV-B irradiated or non-irradiated) were rehydrated. Both drought and UV-B radiation treatments resulted in lower shoot dry matter per plant, but there was no significant interaction between the two treatments. Water stress and UV-B radiation reduced photosynthesis, stomatal conductance and transpiration. However, the amplitude of the effects of both stressors was dependent on the interactions. This resulted in alleviation of the negative effect of drought on photosynthesis and transpiration by UV-B radiation as the water stress intensified. Intercelluar CO(2) concentration was initially reduced in all treatments compared to control plants but it increased with time. Photosynthetic pigments were not affected by UV-B radiation. Water stress reduced photosynthetic pigments only under high UV-B radiation. The decrease was more accentuated for chlorophyll a than for chlorophyll b. As a measure for the maximum efficiency of photosystem II in darkness F (v)/F (m) was used, which was not affected by drought stress but initially reduced by UV-B radiation. Independent of water supply, UV-B radiation increased the activity of pirogalol peroxidase and did not increase the level of malondialdehyde. on the other hand, water stress did not alter the activity of pirogalol peroxidase and caused membrane damage as assessed by lipid peroxidation. The application of UV-B radiation together with drought seemed to have a protective effect by lowering the intensity of lipid peroxidation caused by water stress. The content of proline was not affected by UV-B radiation but was increased by water stress under both low and high UV-B radiation. After 24 h of rehydration, most of the parameters analyzed recovered to the same level as the unstressed plants.