Scientia Forestalis, volume 42, n. 101
Ecophysiology of water stressed Handroanthus impetiginosus (Mart. Ex. DC) Mattos) Seedlings
Ecofisiologia de Mudas de Ipê-Roxo (Handroanthus impetiginosus (Mart. ex. DC.) Mattos) Submetidas a Estresse Hídrico
1Engenheiro Agrônomo, Professor Doutor em fisiologia vegetal. UFERSA - Universidade Federal Rural do Semi-Árido, Departamento de Ciências Vegetais. Caixa Postal 137, 59625-900, Mossoró – e-mail: firstname.lastname@example.org.
Recebido em 31/05/2013 - Aceito para publicação em 06/02/2014
O objetivo desse estudo foi avaliar o comportamento ecofisiológico de Handroanthus impetiginosus em resposta a estresse hídrico e à reidratação. Para isso foi realizado um experimento de supressão de irrigação por um período de 12 dias, até o início da queda das folhas. Após esse período a irrigação foi retomada. As variáveis avaliadas foram fotossíntese, condutância estomática, transpiração, eficiência instantânea e intrínseca de uso da água e o potencial hídrico foliar. As avaliações foram realizadas durante o período de suspensão da irrigação e após sua retomada, até que as taxas de fotossíntese das mudas que foram submetidas à suspensão da irrigação igualassem as das que não foram submetidas. O estresse hídrico afetou a fotossíntese, a transpiração e a condutância estomática, com decréscimo dessas variáveis e rápidas recuperações após a reidratação. A eficiência do uso da água aumentou com o estresse hídrico. H. impetiginosus tem a capacidade de reduzir seu potencial hídrico foliar em condições estressantes, e recupera rapidamente a capacidade fotossintética após o período de estresse.
The objective of this work was to evaluate the ecophysiological behavior of Handroanthus impetiginosus seedlings in response to water stress and rehydration. For this, an experiment was conducted, in which irrigation was suppressed for twelve days, up to the beginning of leaves fall, followed by irrigation resumption. The variables measured were photosynthesis, stomatal conductance, transpiration, instantaneous and intrinsic water use efficiency and leaf water potential. The evaluations were made during the irrigation suspension time and after resumption, until the photosynthesis values from water stressed plants equaled those which did not suffer water shortage. Water stress affected photosynthesis, transpiration and stomatal conductance, with diminution of its levels, and fast recovery after rehydration. The water use efficiency was higher with water stress. H. impetiginosus has the capability of reducing its water potential under stress, and has a fast recovery of photosynthetic rates after the end of the stress.
Handroanthus impetiginosus, Tabebuia impetiginosa or Tabebuia avellanedae (TROPICOS, 2012), popularly known in Brazil as Ipe roxo or pau d’arco roxo is a tree species from the Bignoniaceae, found in Caatinga vegetation (BENEVIDES; CARVALHO, 2009; LIRA et al., 2007; SANTANA; SOUTO, 2011). It has been used for furniture manufacturing and flooring (GEMAQUE et al., 2002), folk medicine (CASTELLANOS et al., 2009; LOURENÇO et al., 2010), urban afforestation (SANTOS et al., 2011) and has a potential as a bee forage plant (BENEVIDES; CARVALHO, 2009). It has also been indicated to be used in forest restoration programs (MAIA, 2004).
The Caatinga plant species present physiological and morphological adaptations to withstand drought (SILVA et al., 2004). These adaptations show up in form, color, metabolism, vital cycles and social organization of all the organisms in this Biome (MAIA, 2004), and the plant composition is conditioned mainly by the water regime (ANDRADE et al., 2009).
Abiotic factors like high irradiances and temperatures and low water or nutrient availability, are all observed in the Caatinga Biome, making it difficult to establish juvenile plants (GONÇALVES et al., 2005; LIBERATO et al., 2006; SANTOS JUNIOR et al., 2006). Among these resources, water is considered the main factor that restraints the establishment potential for plants in general (ARAÚJO et al., 2007; MCLAREN; MCDONALD, 2003; NIPPERT et al., 2006; WEIEGAND et al., 2006;), and particularly for Caatinga plants (CABRAL et al., 2004; MARIANO et al., 2009; SOUZA et al., 2010).
Water stress is the most important problem in agriculture (SHAO et al., 2008), and understanding plant responses to water shortage is of great importance for the development of strategies that improve crop production under water stress (CATTIVELLI et al., FUSSELL et al., 1991; 2008; JALEEL et al., 2009), and also the irrigation programs in semiarid areas (FLEXAS et al., 2004a).
Water deficiency affects plant productive capability, initially due to stomatal closure, with its consequent reduction of CO2 uptake (CHAVESet al., 2002; TANG et al., 2002), but as the stress grows up, a number of metabolic alterations occur (BAKER; ROSENQVIST, 2004; RIBEIRO et al., 2008; SANTOS JUNIOR et al., 2006; TAIZ; ZEIGER, 2009), culminating in leaf fall in deciduous species (SANTANA; SOUTO, 2011). Other aspects related to water stress include reduction of mineral nutrient absorption (FIRMANO et al., 2009; GONZALEZ-DUGO et al., 2010), and impairment of cell (CHAVES et al., 2009) and plant growth (BENGOUGH et al., 2011; SHAO et al., 2008).
There are only a few studies on the physiological responses of Caatinga plants to stresses (TROVÃO, 2007) and also a few studies on photosynthesis recovery capability after water stress (CHAVES et al., 2009; FLEXAS et al., 2006; FLEXASet al., 2004a). In this way, the aim of this study was to evaluate the ecophysiological behavior of Handroanthus impetigionosus in response to water stress and rehydration.
MATERIAL AND METHODS
The experiment was conducted from November 2010 to September 2011, in a greenhouse at the Department of Plant Sciences of the Semiarid Federal Rural University in Mossoro (UFERSA), state of Rio Grande do Norte, Brazil, located at 5º11’S and 37º20’W, and at 18 m altitude. The climate is classificated as Köppen’s BSwh, i.e., dry and very hot (CARMO FILHO et al., 1991), the mean annual temperature is 27.4 and the relative humidity is 68.9%. The greenhouse was covered with plastic film and 50% shade cloth.
The fruits were collected from mother plants at the UFERSA campus in Mossoro, the seeds were extracted and three seeds were planted in each plastic bag with 1.5L substrate capacity. The substrate used was a Neossolo Quartzarenico Distrofico (by Brazilian system of soil classification), also collected at the UFERSA campus, in an area under natural forest restoration, which was mixed with 25% manure.The plants were thinned 40 days after seeding, leaving one per bag. The irrigation was made daily, always at the end of the afternoon.
When seedlings reached nine months, in the dry season, an experiment in random complete blocks was installed, with two water regimes (with and without water stress) and three replications. Each replication was represented by three plants. Irrigation was suspended for 12 days, up to the beginning of leaves fall, and resumed after that. Evaluations were made at a three-day interval, since before irrigation suspension and until the photosynthetic rates from the two water regimes were equal. The variables measured were pre-dawn and midday leaf water potential (Ψw; MPa); photosynthesis (A; µmol CO2 m-2 s-1); stomatal conductance (gs; mol H2O m-2 s-1) and transpiration (E; mmol H2O m-2 s-1).
For the photosynthesis measurement we used a LI-6400 photosynthesis system (LI-COR Biosciences) with CO2 levels fixed at 400µmoles m-2 s-1 and light intensity at 1500µmoles m-2 s-1 of PAR. The instantaneous water use efficiency (A/E) was determined and also intrinsic water use efficiency (A/gs) (MEDRANO; GALMÉS, 2009). For water potential measurement we used a pressure pump (PMS Instrument).
The results were submitted to variance analysis by the F test, 5% probability, in each evaluation time, with the SISVAR statistical software (FERREIRA, 2008).
RESULTS AND DISCUSSION
The beginning of leaves fall occurred on the 12th day, then irrigation was resumed and, after six days, the photosynthesis rates between the two water regimes were equal.
Minimum pre-dawn and midday water potential observed were -1.9 and -3.0 MPa (Figure 1) which indicates a good investment capability as a drought resistance strategy. Similar water potential levels were observed by Dombroski et al. (2011) with other Caatinga species in the dry season. For Caesalpinia ferrea e Calliandra spinosa, the authors observed a mean leaf Ψw of -1 and -1.3 Mpa in pre-dawn and -2.2 and -2.7 Mpa at midday, respectively. In the same work, the authors observed that, for other tree species, the water potential ranged from -0.5 Mpa to -3.5 Mpa, characterizing varied investment strategies. Lowering internal Ψw allows water absorption to occur for some time after the rain, with consequent stomatal opening and photosynthesis (LARCHER, 2004).
Irrigation suspension affected pre-dawn and midday water potential in different ways. In pre-dawn there was a significant difference of Ψw between the two water regimes after three days of suspension, indicating the beginning of water deficit in soil. This difference remained until the 12th day when irrigation was resumed and, on the 15th day, no more Ψw differences between the treatments were observed. For midday Ψw, a difference between treatments was seen only on the 12th day, so the plants kept a leaf Ψw near -2.0MPa in less severe conditions; but when water availability was even more reduced, the plant reduced its leaf Ψw even more. Midday leaf Ψw recovery occurred only six days after irrigation returned, which may indicate a loss in xylem water conductivity (BRODRIBB; COCHARD, 2009).
In figures 2A and 2B the relationship between A and gs with pre-dawn and midday leaf Ψw is shown. It can be seen that there is a pattern, both for A and for gs relationship with leaf Ψw. For leaf Ψw values in pre-dawn higher than -1.0 MPa, and in midday, higher than -2.5 MPa, the relation is very weak, with small Ψw variation related to strong variations in gs and A. Bellow these Ψw threshold values, A and gs values are lower than 7.0 µmoles CO2.m-2.s-1 for A and lower than 0.05 mmoles H2O.m-2.s-1 for gs. Similar results were obtained for Chilops and Encelia, both desert bushes, by Odening et al. (1974). Values of gs below 0.10 – 0.15 mmoles H2O.m-2.s-1 are considered indicators of severe water stress (FLEXAS et al., 2004a).
There are strong differences in stomatal behavior among species related to water deficits in soil and atmosphere (BOND et al., 1999). The stomatal conductance is affected by a series of factors related to plant water status, like leaves’ and roots’ water potential, abscisic acid levels and other hormones, xylem hydraulic conductivity (MEDRANO et al., 2002), the photosynthetic metabolism type (OSBORNE; SACK, 2012), and also by environmental factors, like the vapour pressure deficit (YU et al., 2009), temperature (SALVUCCI; CRAFTS-BRANDNER, 2004), atmosphere CO2 levels (MIRI et al., 2012), and light availability and intensity (HORTON et al., 1996). Gs responds to a complex net of factors linked to the plant water status so that Flexas et al. (2004b) propose the use os gs as an indicator of plants water stress level. Leaf Ψw is a strong regulator of gs and, in consequence, of A.
A mild water stress affects A (Fig 3a) and gs (Fig. 3b), which affects directly E (Fig. 3c). A decrease in A, gs and E three days from the beginning of irrigation suspension was observed, but without a decrease in Ci. Water stress can affect A related to CO2 limitation (Fig. 3c), caused by the decrease in gs, as was observed in the present work, but in this case there would be a decrease in Ci, suggesting that the limitation of A is not from CO2 shortage. Although the reliability of Ci mensuration under water stress has been questioned (Flexas et al.; 2004b; Lawlor and Tezara; 2009), the possibility of non gs limitations cannot be disregarded. In more severe cases, the water deficit has been reported to cause decrease in A by a restriction of mesophil conductance of CO2 (Lawlor and Tezara, 2009); metabolic alterations in chlorophyll content; ATP levels; content of Ribulose bisphosphate; Rubisco activity (LAWLOR, 2002; BOTA et al., 2004; Flexas et al., 2004b), oxidative damage and/or photoinhibition (Galmés et al., 2007).
Six days after irrigation resumption, the treatments showed no more significant differences among the variables A, gs, E and Ci (figure 4). Similar results were found for Minquartia guianensis (LIBERATO et al., 2006), also with recuperation six days after irrigation resumption. In a work with Carapa guianensis, Gonçalves et al. (2009) observed a recuperation of A levels eight days after the water levels were restored. Despite the beginning of leaves fall, the full recuperation of A is an evidence of a low damage to the photosynthetic apparatus, different of what was observed in other species (MIYASHITA et al.,2005). In cases of severe water stress, it may occur that the plants take a long time or do not recover its pre-stress photosynthetic capability (FLEXAS et al., 2004a).
Instantaneous (A/E) and intrinsic (A/gs) water use efficiency were affected by the treatments. Higher values at the 6th, 9th and 12th days after irrigation suspension were observed (Fig 4A and 4B). Gonçalves et al. (2009), in a work with Carapa guianensis did not observe diferences in A/E between irrigated and non irrigated plants, with maximum values near 4.0 mmol CO2.mol H2O-1, lower than the highest values observed in the present work (average of 5.7 mmol CO2.mol H2O-1). The higher H. impetiginosus efficiency may be due to the fact that C guianensis is a humid tropical climate plant, in which water is not a scarce resource, when compared to the Caatinga climate.
Six days after irrigation resumption, A/E and A/gs values equaled the control treatment (Fig. 4), which means that the water use efficiency observed during the water restriction period was not kept after irrigation resumption. A raise in A/E in moderate water stress conditions had already been observed (SAUSEN; ROSA, 2010). Still when the stress is severe, with the decrease of mesophile cells water content, the metabolism is impaired, affecting photosynthesis, and water use efficiency decreases (TAIZ; ZEIGER, 2009).
There was a linear relationship between A and gs for gs values below 200 mmol.m-2.s-1, (data not shown, R2 = 0.91) , Flexas et al., 2004a indicates that A is possibly limited mainly by gs in this range, but there are other factors that can limit A, especially under gs values of 50 to 100 mmol.m-2.s-1, like those cited before. Costa and Marenco (2007) and Gonçalveset al. (2009) in works with C. guianensis, and Janoudi et al. (1993) with pumpkin also observed a restraint in A for gs values below 256 mmol.m-2.s-1.
The behavior of the A/gs relationship followed a similar pattern to the three stages pattern described by Flexas et al. (2004a), as a characteristic pattern for plants in general, with a small decrease of A until 150 mmol H2O.m².s-1, a stronger reduction between 150 and 50 mmol H2O.m².s-1, and an even higher reduction below this gs level. This tendency was also observed for grapevines by Medrano et al. (2002), which is a species well adapted to water stress (FLEXAS et al., 2004a).
H. impetiginosus has a full photosynthetic recovery after a severe water stress.
Water stress affects photosynthesis, transpiration and stomatal conductance, with the decrease of these variables; and fast recovery after rehydration.
Instantaneous and intrinsic water use efficiency raise under water stress.
To FAPEMAT - Fundação de Amparo à Pesquisa do Estado de Mato Grosso, which enabled the Matas de Galeria Project, to the Programa de Pós-graduação em Ecologia e Conservação - UNEMAT, and the entire staff of the Laboratório de Ecologia Vegetal, at Universidade do Estado de Mato Grosso, Nova Xavantina campus.
ANDRADE, W. M.; LIMA, E. A.; RODAL, M. J. N.; ENCARNAÇÃO, C. R. F.; PIMENTEL, R. M. M. Influência da precipitação na abundância de populações de plantas da Caatinga. Revista de Geografia, Recife, v. 26, n. 2, p. 161-184, 2009.
ARAÚJO, E. E.; CASTRO, C. C.; ALBUQUERQUE, U. P. Dynamics of Brazilian Caatinga- A review concerning the plants, environment and people. Functional Ecosystems and Communities, United Kingdom, v. 1, n. 1, p. 15-28, 2007.
BAKER, N. R.; ROSENQVIST, E. Applications of chlorophyll ?uorescence can improve crop production strategies: an examination of future possibilities. Journal of Experimental Botany, Oxford, v. 55, n. 403, p. 1607-1621, 2004.
BENEVIDES, D. S.; CARVALHO, F. G. Levantamento da flora apícola presente em áreas de Caatinga do município de Caraúbas- RN. Sociedade e Território, Natal, v. 21, n. 1-2, p. 44-54, 2009.
BENGOUGH, A. G.; MCKENZIE, B. M.; HALLETT, P. D.; VALENTINE, T. A. Root elongation, water stress, and mechanical impedance: a review of limiting stresses and bene?cial root tip traits. Journal of Experimental Botany, Oxford, v. 62, n. 1, p. 59-68, 2011.
BOND, B. J.; KAVANAGH, K. L. Stomatal behavior of four woody species in relation to leaf-specific hydraulic conductance and threshold water potential. Tree Physiology, Victoria, v. 19, n. 8, p. 503-510, 1999.
BOTA, J.; MEDRANO, H.; FLEXAS, J. Is photosynthesis limited by decreased Rubisco activity and RuBP content under progressive water stress? New Phytologist, Oxford, v. 162, n. 3, p. 671-681, 2004.
BRODRIBB, T. J.; COCHARD, H. Hydraulic Failure De?nes the Recovery and Point of Death in Water-Stressed Conifers. Plant Physiology, Rockville, v. 149, n. 1, p. 575-584, 2009.
CABRAL, E. L.; BARBOSA, D. C. A.; SIMABUKURO, E. A. Crescimento de plantas jovens de Tabebuia áurea (Manso) Benth. & Hook. f. ex. S. Moore submetidas a estresse hídrico. Acta Botanica Brasilica, Feira de Santana, v. 18, n. 2, p. 241-251, 2004.
CARMO FILHO, F.; ESPÌNOLA SOBRINHO, J.; MAIA NETO, J. M. Dados climatológicos de Mossoró: um município semi-árido nordestino. Mossoró: ESAM, 1991. 121 p.
CASTELLANOS, J. R. G.; PRITO, J. M.; HEINRICH, M. Red Lapacho (Tabebuia impetiginosa) - a global ethnopharmacological commodity? Journal of Ethnopharmacology, Clare, v. 121, n. 1, p. 1-13, 2009.
CATTIVELLI, L.; RIZZA, F.; BADECK, F. W.; MAZZUCOTELLI, E.; MASTRANGELO, A. M.; FRANCIA, E.; MARE, C.; TONDELLI, A.; STANCA, A. M. Drought tolerance improvement in crop plants: An integrated view from breeding to genomics. Field Crops Research, Amsterdam, v. 105, n. 1-2, p. 1-14, 2008.
CHAVES, M. M.; FLEXAS, J.; PINHEIRO, C. Photosynthesis under drought and salt stress: regulation mechanisms from whole plant to cell. Annals of Botany, Oxford, v. 103, n. 4, p. 551-560, 2009.
CHAVES, M. M.; PEREIRA, J. S.; MAROCO, J.; RODRIGUES, M. L.; RICARDO, C. P. P.; OSORIO, M. L.; CARVALHO, I.; FARIA, T.; PINHEIRO, C. How plants cope with water stress in the ?eld. Photosynthesis and growth. Annals of Botany, Oxford, v. 89, n. 7, p. 907-916, 2002.
COSTA, G. F.; MARENCO, R. A. Fotossíntese, condutância estomática e potencial hídrico foliar em árvores jovens de andiroba (Carapa guianensis). Acta Amazonica, Manaus, v. 3, n. 2, p. 229-234, 2007.
DOMBROSKI, J. L. D. PRAXEDES, S. C.; FREITAS, R. M. O.; PONTES, F. M. Water relations of Caatinga trees in the dry season. South African Journal of Botany, África do Sul, v. 77, n. 2, p. 430-434, 2011.
FERREIRA, D. F. SISVAR: um programa para análises e ensino de estatística. Revista Symposium, São Paulo, v. 6, n. 2, p. 36-41, 2008.
FIRMANO, R. S.; KUWAHARA, F. A.; SOUZA, G. M. Relação entre adubação fosfatada e deficiência hídrica em soja. Ciência Rural, Santa Maria, v. 39, n. 7, p. 1967-1973, 2009.
FLEXAS, J.; BOTA, J.; GALMÉS, J.; MEDRANO, H.; RIBAS-CARBÓ, M. Keeping a positive carbon balance under adverse conditions: responses of photosynthesis and respiration to water stress. Physiologia Plantarum, Copenhagem, v. 127, n. 3, p. 343-352, 2006.
FLEXAS, J.; BOTA, J.; CIFRE, J.; ESCALONA, J. M.; GALMÉS, J.; GULÕAS, J.; LEFI, E.; MARTÍNEZ-CAÑELLAS, S. F.; MORENO, M. T.; RIBAS-CARB, M.; RIERA, D.; SAMPOL, B.; MEDRANO, H. Understanding down-regulation of photosynthesis under water stress: future prospects and searching for physiological tools for irrigation management. Annals of Applied Biology
FLEXAS, J.; BOTA, J.;CIFRE,J; ESCALONA, J. M.; GALMÉS,J.; GULIAS, J.; LEFI, E.; MARTÍNEZ-CANELLAS, S. F.; MORENO, M. T.; RIBAS-CARBÓ, M.; RIERA, D. SAMPOL, B.; MEDRANO, H. Understanding down-regulation of photosynthesis under water stress: future prospects and searching for physiological tools for irrigation management. Annals of Applied Biology, v.144, n. 3, p.273-283, 2004b.
FUSSELL, L. K.; BIDINGER, F. R.; BIELER, P. Crop physiology and breeding for drought tolerance: research and development. Field Crops Research, Amsterdam, v. 27, n. 3, p. 183-199, 1991.
GALMÉS, J.; ABADÍA, A.; MEDRANO, H.; FLEXAS, J. Photosynthesis and photoprotection responses to water stress in the wild extinct plant Lysimachia minoricensis. Environmental and Experimental Botany, Oxford, v. 60, n. 3, p. 308-317, 2007.
GEMAQUE, R. C. R.; DAVIDE, A. C.; FARIA, J. M. R. Indicadores de maturidade fisiológica de sementes de ipê-roxo (Tabebuia impetiginosa). Cerne, Lavras, v. 8, n. 2, p. 84-91, 2002.
GONÇALVES, J. F. C.; BARRETO, D. C. S.; SANTOS JUNIOR, U. M.; FERNANDES, A. V.; SAMPAIO, P. T. B.; BUCKERIDGE, M. S. Growth, photosynthesis and stress indicators in young rosewood plants (Aniba rosaeodora Ducke) under different light intensities. Brazilian Journal of Plant Physiology, Campos dos Goytacazes, v. 17, n. 3, p. 325-334, 2005.
GONÇALVES, J. F. C.; SILVA, C. E. M.; GUIMARÃES, D. G. Fotossíntese e potencial hídrico foliar de plantas jovens de andiroba submetidas à deficiência hídrica e à reidratação. Pesquisa Agropecuária Brasileira, Brasília, v. 44, n. 1, p. 8-14, 2009.
GONZALEZ-DUGO, V.; DURAND, J.; GASTAL, F. Water de?cit and nitrogen nutrition of crops. A review. Agronomy Sustainable Development, Baghdad, v. 30, n. 3, p. 529-544, 2010.
HORTON, P.; RUBAN, A. V.; WALTERS. R. G. Regulation of light harvesting in green plants. Annual Review of Plant Physiology and Plant Molecular Biology, Palo Alto, v. 47, n. 1, p. 655-684, 1996.
JALEEL, C. A.; MANIVANNAN, P.; WAHID, A.; FAROOQ, M.; AL-JUBURI, H. J.; SOMASUNDARAM, R.; PANNEERSELVAM, R. Drought Stress in Plants: A Review on Morphological Characteristics and Pigments Composition. International Journal of Agriculture & Biology, Islamabad, v. 11, n. 1, p. 100-115, 2009.
JANOUDI, A. K.; WIDDERS, I. E.; FLORE, J. A. Water Deficits and Environmental Factors Affect Photosynthesis in Leaves of Cucumber (Cucumis sativus). Journal of the American Society for Horticultural Science, Alexandria, v. 118, n. 3, p. 366-370, 1993.
LARCHER, W. Ecofisiologia vegetal. São Carlos: RIMA, 2004.
LAWLOR, D. W. Limitation to Photosynthesis in Water-stressed Leaves: Stomata vs. Metabolism and the Role of ATP. Annals of Botany, Oxford , v. 89, n. 7, p. 871-885, 2002.
LAWLOR, D. W.; TEZARA, W. Causes of decreased photosynthetic rate and metabolic capacity in water-deficient leaf cells: a critical evaluation of mechanisms and integration processes. Annals of Botany, Oxford, v. 103, n. 4, p. 561-579, 2009.
LIBERATO, M. A. R.; GONÇALVES, J. F. C.; CHEVREUIL, L. R.; NINA JUNIOR, A. R.; FERNANDES, A. V.; SANTOS JUNIOR, U. M. Leaf water potential, gas exchange and chlorophyll a ?uorescence in acariquara seedlings (Minquartia guianensis Aubl.) under water stress and recovery. Brazilian Journal of Plant Physiology, Campos dos Goytacazes, v. 18, n. 2, p. 315-323, 2006.
LIRA, R. B.; MARACAJÁ, P. B.; MIRANDA, M. A. S.; SOUSA, D. D.; MELO, S. B.; AMORIM, L. B. Estudo da composição florística arbóreo-arbustivo na floresta nacional de Açu no semi árido do RN Brasil. Agropecuária Científica no Semi-Árido, Patos, v. 3, n. 3, p. 23-30, 2007.
LOURENÇO, J. A.; PITANGUI, C. P.; JORDÃO, A. A.; VANNUCCHI, H.; CECCHI, A. O. Ausência de mutagenicidade e antimutagenicidade do extrato obtido das flores do ipê-roxo <[i>Tabebuia impetiginosa (Mart. ex DC.) Standl.]. Revista Brasileira Plantas Medicinais, Botucatu, v. 12, n. 4, p. 414-420, 2010.
MAIA, N. G. Caatinga: árvores e arbustos e suas utilidades. São Paulo: Editora Leitura & Arte, 2004. 413 p.
MARIANO, K. R.; BARRETO, L. S.; SILVA, A. H. B.; NEIVA, G. K. P.; AMORIM, S. Fotossíntese e tolerância protoplasmática foliar em myracrodruon urundeuva fr. all. submetida ao déficit hídrico. Revista Caatinga, Mossoró, v. 22, n. 1, p. 72-77, 2009.
MCLAREN, K. P.; MCDONALD, M. A. The effects of moisture and shade on seed germination and seedling survival in a tropical dry forest in Jamaica. Forest Ecology and Management, Amsterdam, v. 183, n. 1-3, p. 61-75, 2003.
MEDRANO, H.; ESCALONA, J. N.; BOTA, J.; GULÍAS, J.; FLEXAS, J. Regulation of photosynthesis of C3 plants in response to progrssive drought: stomatal conductance as a reference parameter. Annals of Botany, Oxford, v. 89, n. 7, p. 895-905, 2002.
MEDRANO, H.; FLEXAS, J.; GALMÉS, J. Variability in water use efficiency at the leaf level among Mediterranean plants with different growth forms. Plant and Soil, Baltimore, v. 317, n. 1-2, p. 17-29, 2009.
MIRI, H. R.; RASTEGAR, A.; BAGHERI, A. R. The impact of elevated CO2 on growth and competitiveness of C3 and C4 crops and weeds. European Journal of Experimental Biology, Islamabad, v. 2, n. 4, p. 1144-1150, 2012.
MIYASHITA, K.; TANAKAMARU, S.; MAITANI, T.; KIMURA, K. Recovery responses of photosynthesis, transpiration, and stomatal conductance in kidney bean following drought stress. Environmental and Experimental Botany, Elmsford v. 53, n. 2, p. 205-214, 2005.
NIPPERT, J. B.; KNAPP, A. K.; BRIGGS, J. M. Intra-annual rainfall variability and grassland productivity: can the past predict the future? Plant Ecology, Oxford, v. 184, n. 1, p. 65-74, 2006.
ODENING, W. R.; STRAIN, B. R.; OECHEL, W. C. The effect of decreasing water potential on net CO2 exchange of intact desert shrubs. Ecology, Oxford, v. 55, n. 5, p. 1086-1095, 1974.
OSBORNE, C. P.; SACK, L. Evolution of C4 plants: a new hypothesis for an interaction of CO2 and water relations mediated by plant hydraulics. Philosophical Transactions of the Royal Society B: Biological Sciences, v. 367, n. 1588, p. 583-600, 2012.
RIBEIRO, R. V.; SANTOS, M. G.; MACHADO, E. C.; OLIVEIRA, R. F. Photochemical heat-shock response in common bean leaves as affected by previous water de?cit. Russian Journal of Plant Physiology, Moscow, v. 55, n. 3, p. 350-358, 2008.
SALVUCCI, M. E.; CRAFTS-BRANDNER, S. J. Inhibition of photosynthesis by heat stress: the activation state of Rubisco as a limiting factor in photosynthesis. Acta Physiologiae Plantarum, Kraków, v. 120, n. 2, p. 179-186, 2004.
SANTANA, J. A. S.; SOUTO, J. S. Produção de serapilheira na Caatinga da região semi-árida do Rio Grande do Norte, Brasil. IDESIA, v. 29, n. 2, p. 87-94, 2011.
SANTOS, A. C. B.; SILVA, M. A. P.; SOUZA, R. K. D. Levantamento florístico das espécies utilizadas na arborização de praças no município de Crato-CE. Caderno de Cultura e Ciência, Crato, v. 10, n. 1, p. 13-18, 2011.
SANTOS JUNIOR, U. M.; GONÇALVES, J. F. C.; FELDPAUSCH, T. R. Growth, leaf nutrient concentration and photosynthetic nutrient use ef?ciency in tropical tree species planted in degraded areas in central Amazonia. Forest Ecology and Management, Amsterdam, v. 226, n. 1-3, p. 299-309, 2006.
SAUSEN, T. L.; ROSA, L. M. G. Growth and carbon assimilation limitations in Ricinus communis (Euphorbiaceae) under soil water stress conditions. Acta Botanica Brasilica, Feira de Santana, v. 24, n. 3, p. 648-654. 2010.
SHAO, H.; CHU, L.; JALEEL, C. A.; ZHAO, C. Water-de?cit stress-induced anatomical changes in higher plants. Comptes Rendus Biologies, v. 331, n. 3, p. 215-225, 2008.
SILVA, E. C.; NOGUEIRA, R. J. M. C.; AZEVEDO NETO, A. D.; BRITO, J. Z.; CABRAL, E. L. Aspectos ecofisiológicos de dez espécies em uma área de Caatinga no município de Cabaceiras, Paraíba, Brasil. Iheringia Série Botânica, v. 59, n. 2, p. 201-205, 2004.
SOUZA B. D.; RODRIGUES, B. M.; MEIADO, M. V.; SANTOS, M. G. Water relations and chlorophyll fluorescence responses of two leguminous trees from the Caatinga to different watering regimes. Acta Physiologiae Plantarum, v. 32, n. 2, p. 235-244, 2010.
TAIZ, L.; ZEIGER, E. Fisiologia Vegetal. 4.ed. Porto Alegre: Artmed, 2009. 820 p.
TANG, A. C.; KAWAMITSU, Y.; KANECHI, M.; BOYER, J. S. Photosynthetic oxygen evolution at low water potential in leaf discs lacking an epidermis. Annals of Botany, Oxford, v. 89, n. 7, p. 86-870, 2002.
TROPICOS Missouri Botanical Garden. Disponível em:
TROVÃO, D. M. B. M.; FERNANDES, P. D.; ANDRADE, L. A.; NETO, J. D. Variações sazonais de aspectos fisiológicos de espécies da Caatinga. Revista Brasileira de Engenharia Agrícola e Ambiental, Campina Grande, v. 11, n. 3, p. 307-311, 2007.
WEIEGAND, K.; SALTZ, D.; WARD, D. A patch-dynamics approach to savanna dynamics and woody plant encroachment-insights from an arid savanna. Perspectives in Plant Ecology, Evolution and Systematics, Amsterdam, v. 7, n. 4, p. 229-242, 2006.
YU, D. J.; KIM, S. J.; LEE, H. J. Stomatal and non-stomatal limitations to photosynthesis in field-grown grapevine cultivars. Biologia Plantarum, New York, v. 53, n. 1, p. 133-137, 2009.