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The first symptom of aluminum (Al) toxicity is the inhibition of root growth, which has been associated with low leaf hydration, with negative consequences for leaf gas exchange including stomatal conductance (gs) observed in many plant species. Here we asked whether low leaf hydration occurs before or after the inhibition of root growth of Citrus × limonia Osbeck (‘Mandarin’ lime) cultivated for 60 days in nutrient solution with 0 and 1480 μM Al. The length, diameter, surface area and biomass of roots of plants exposed to Al were lower than control plants only at 30 days after treatments (DAT). Until the end of the study, estimated gs (measured by sap flow techniques) was lower than in control plants from 3 DAT, total plant transpiration (Eplant) and root hydraulic conductivity (Lpr) at 7 DAT, and midday leaf water potential (Ψmd) and relative leaf water content at 15 DAT. Abscisic acid (ABA) in leaves was twofold higher in Al-exposed plants 1 DAT, and in roots a twofold higher peak was observed at 15 DAT. As ABA in leaves approached values of control plants after 15 DAT, we propose that low gs of plants exposed to Al is primarily caused by ABA, and the maintenance of low gs could be ascribed to the low Lpr from 7 DAT until the end of the study. Therefore, the low leaf hydration in ‘Mandarin’ lime exposed to Al does not seem to be caused by root growth inhibition or by a simple consequence of low water uptake due to a stunted root system.

Made available in DSpace on 2022-04-30T20:25:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Considering that water deficit is one of the main environmental factors responsible for low soybean yield and that nitric oxide (NO) has been shown to be a fundamental part of plant defense signaling during stress, the aim of the present study was to evaluate the effect of seed priming with nitric oxide on the induction of water deficit tolerance during the initial development of soybean. Thus, seeds were treated with 0 (water only), 50, 100 or 250 μmol.L-1 sodium nitroprusside for 6 hours. Additionally, untreated seeds were used. After drying, the seeds were placed in containers filled with a commercial substrate mixture and vermiculite and irrigated to 100% and 50% field capacity. Biometric and biochemical evaluations (pigment and proline contents) were performed after 14 days. It was concluded that pretreatment of soybean seeds with 50 to 250 μmol.L-1 SNP attenuated the effects of water deficit on stem growth, leaf area, and shoot dry matter and induced carotenoid biosynthesis. The accumulation of proline in the leaves was pronounced in the treatments with 100 and 250 μmol.L-1 SNP, while 100 μmol.L-1 SNP induced proline accumulation in the roots. São Paulo State University São Paulo State University

Made available in DSpace on 2018-12-11T17:38:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-11-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Stomatal aperture generally increases in response to low vapor pressure deficit (VPD) and decreases at high VPD. Aluminum (Al) inhibits root growth, indirectly exposing the roots to low water availability, which may decrease leaf hydration and, consequently, the stomatal conductance (gs). In this study, Citrus limonia (‘Rangpur’ lime) was grown in nutrient solution with 1480 μM Al for 90 days, and we expected that the presence of Al could prevent gs from responding to VPD. As expected, gs did not respond to the increase in VPD in plants exposed to Al. Aluminum also reduced the relative water content and midday leaf water potential (Ψmd) after 60 and 90 days. The CO2 assimilation rate (A) followed the same response pattern exhibited by gs, the estimation of the carboxylation efficiency was not reduced in plants exposed to Al and measured under drier air, while photochemical responses were slightly reduced in plants exposed to Al, indicating that the Al-induced decrease in A was dependent on gs and less ascribed to low photochemical performance. Like in drought conditions, the long-term exposure to Al reduces leaf hydration and compromises gs responses to the atmosphere, eventually impairing A in ‘Rangpur’ lime plants. Programa de Pós-Graduação em Biologia Vegetal Universidade Estadual Paulista (UNESP) Instituto de Biociências Departamento de Botânica, Av. 24-A, 1515 Universidade Estadual Paulista (UNESP) Instituto de Biociências Departamento de Botânica, Av. 24-A, 1515 Programa de Pós-Graduação em Biologia Vegetal Universidade Estadual Paulista (UNESP) Instituto de Biociências Departamento de Botânica, Av. 24-A, 1515 Universidade Estadual Paulista (UNESP) Instituto de Biociências Departamento de Botânica, Av. 24-A, 1515 CNPq: 309149/2017-7

Made available in DSpace on 2022-04-30T05:43:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-02-01 Chemical ripeners are being used to anticipate the ripening process of sugarcane. These products act in specific enzyme or protein systems of plants, altering their functionality. However, these products can seriously affect the development of non-target species. In light of the proximity of permanent preservation areas to sugarcane plantations, we aimed at understanding the effect of simulated drift of chemical ripeners on 18-month age seedlings of Citharexylum myrianthum, a Brazilian native tree species. The experiment was conducted under semi-controlled conditions using a randomized block design with six replications. Treatments consisted of a 6x2 factorial arrangement, corresponding to six concentrations of glyphosate and sulfometuron-methyl, equivalent to 0, 5, 15, 30, 45, and 60% of commercial dose recommended for sugarcane. Plant height, stem diameter, number of leaves, total chlorophyll content, chlorophyll a fluorescence, and gas exchange were measured at 7, 30, and 60 days after application (DAA),. The leaf area and dry mass of plants were also measured at the end of the experimental period (60 DAA),. Both ripeners caused visual symptoms of phytointoxication in C. myrianthum, which were accompanied by alterations in gas exchange until 30 DAA. At 60 DAA, all plants treated with glyphosate recovered their photosynthetic capacity, without detrimental effect on their initial development, while those treated with 60% of sulfometuron-methyl showed limited growth in height coupled to super sprout due to the death of apical meristem. Despite no significant difference in total dry mass, the development of these plants was affected. Universidade Estadual Paulista 'Júlio de Mesquita Filho' Instituto de Biociências Departamento de Botânica, Avenida 24 A, 1 515, Bela Vista Universidade Estadual Paulista 'Júlio de Mesquita Filho' Departamento de Biologia Aplicada à Agropecuária, Via de Acesso Prof. Paulo Donato Castellane, s/n Bairro Rural Universidade Estadual Paulista 'Júlio de Mesquita Filho' Departamento de Fitossanidade, Via de Acesso Prof. Paulo Donato Castellane, s/n Bairro Rural Universidade Estadual Paulista 'Júlio de Mesquita Filho' Instituto de Biociências Departamento de Botânica, Avenida 24 A, 1 515, Bela Vista Universidade Estadual Paulista 'Júlio de Mesquita Filho' Departamento de Biologia Aplicada à Agropecuária, Via de Acesso Prof. Paulo Donato Castellane, s/n Bairro Rural Universidade Estadual Paulista 'Júlio de Mesquita Filho' Departamento de Fitossanidade, Via de Acesso Prof. Paulo Donato Castellane, s/n Bairro Rural

Made available in DSpace on 2018-11-26T17:51:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01. Added 1 bitstream(s) on 2021-07-15T14:32:15Z : No. of bitstreams: 1 S0006-87052018000100013.pdf: 1289889 bytes, checksum: 8cc29053b58bd5468d8c3db43ea4a50a (MD5) It is well known that phytochromes mediate a wide range of photomorphogenic processes in plants. In addition, many studies have demonstrated the involvement of phytochromes as part of abiotic stress signaling responses. However, little is known about cadmium (Cd) stress regulation by phytochromes. Thus, in this study, we used the phyA (far red-insensitive; fri), phyB1 (temporary red-insensitive; tri) and phyB2 (phyB2) tomato (Solanum lycopersicum L.) mutants to investigate the roles of these three phytochromes on Cd stress responses. The plants were grown over a 21-d period in the presence of Cd. We evaluated plant growth, Cd and chlorophyll content and anatomical changes in the leaves. The results indicated that all genotypes were affected by Cd and showed reduced growth of the shoots and roots, as well as reduced chlorophyll content. The accumulation of Cd was similar for all genotypes, and a higher Cd content was found in roots. Anatomical analysis of the vascular bundles revealed that fri and tri seem to be more disrupted by Cd. Overall, these results indicate that phytochromes do not determine Cd stress tolerance in tomato plants. Univ Estadual Paulista, Fac Ciencias Agr & Vet, Dept Biol Aplicada Agr, Jaboticabal, SP, Brazil Univ Estadual Paulista, Fac Ciencias Agr & Vet, Dept Prod Vegetal, Jaboticabal, SP, Brazil Univ Estadual Paulista, Fac Ciencias Agr & Vet, Dept Biol Aplicada Agr, Jaboticabal, SP, Brazil Univ Estadual Paulista, Fac Ciencias Agr & Vet, Dept Prod Vegetal, Jaboticabal, SP, Brazil

Made available in DSpace on 2020-12-12T02:32:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 In acidic soils, aluminium (Al) occurs as Al3+, which is phytotoxic. One of the most conspicuous symptoms of Al toxicity is the root growth inhibition, which can lead to low water uptake and consequent reduction in leaf hydration and gas exchange. However, fibrous xylem vessels have been observed in roots of 'Rangpur' lime plants (Citrus limonia L.) when exposed to Al, which could affect the functioning of aquaporins, ultimately reducing their expression. We confirmed a decrease of CO2 assimilation (A), stomatal conductance (gs), transpiration (E) and relative leaf water content (RWC) in 3-month-old C. limonia plants exposed to 1480 μM Al in nutrient solution for 90 days. The estimated hydraulic conductivity from soil to the leaf (KL) and leaf water potential (Ψw) also showed low values, although not consistently reduced over time of Al exposure. The relative expression of aquaporin genes belonging to PIP family (PIP1-1, PIP1-2 and PIP2) showed downregulation for ClPIP1-1 and ClPIP2 and upregulation for ClPIP1-2 in plants exposed to Al. Furthermore, ClPIP1-1 was positively correlated with A and gs in plants exposed to Al. Therefore, downregulation of ClPIP1-1 and ClPIP2 in roots of 'Rangpur' lime plants could be associated with the low leaf hydration of this species when exposed to Al. Programa de Pós-Graduacąõ em Ciências Biológicas (Biologia Vegetal) Universidade Estadual Paulista UNESP Instituto de Biociências Departamento de Botânica, Av. 24-A, 1515 Escola Superior de Agricultura 'Luiz de Queiróz' Universidade de Saõ Paulo ESALQ-USP Departamento de Ciências Biológicas, Av. Pádua Dias, 11 Departamento de Botânica Universidade Estadual Paulista UNESP Instituto de Biociências, Av. 24-A, 1515 Programa de Pós-Graduacąõ em Ciências Biológicas (Biologia Vegetal) Universidade Estadual Paulista UNESP Instituto de Biociências Departamento de Botânica, Av. 24-A, 1515 Departamento de Botânica Universidade Estadual Paulista UNESP Instituto de Biociências, Av. 24-A, 1515

Made available in DSpace on 2021-06-25T11:11:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-01 Aluminum (Al)-induced decrease in leaf hydration has been associated with low gas exchange, especially stomatal conductance (gs). However, the mechanisms explaining these responses are unclear. Citrus limonia was exposed to 0 and 1480 μM Al in nutrient solution for 90 days to test whether the low gs and leaf hydration in plants exposed to Al is associated with increased 9-cis-epoxycarotenoid dioxygenase (NCED) gene expression and abscisic acid (ABA) biosynthesis. Relative leaf water content (RWC), water potential (Ψw) and gas exchange in the leaves, as well as leaf and root ClNCED3, ClNCED1 and ClNCED5 expression and accumulation of ABA and its metabolites (phaseic acid, dihydrophaseic acid, (+)-7′-hydroxy-ABA and ABA-β-D-glucosyl ester) were measured. Aluminum up-regulated ClNCED3 and induced ABA accumulation in the roots before impairments in leaf water status (low Ψw, RWC and gs) could be observed. Leaf ABA concentration increased from 7 to 90 days and this could be partially explained by the up-regulation of ClNCED3, ClNCED1 and ClNCED5 in this organ. Stomatal closure occurred concomitantly with the increase of ABA concentration, and this result provides further evidence of the role of ABA modulation of plant hydration under Al stress. Programa de Pós-Graduação em Biologia Vegetal Departamento de Biodiversidade Instituto de Biociências Universidade Estadual Paulista UNESP, Av. 24-A, 1515 Departamento de Ciências Biológicas Escola Superior de Agricultura “Luiz de Queiróz” Universidade de São Paulo ESALQ-USP, Av. Pádua Dias, 11 Cranfield Soil and Agrifood Institute Cranfield University, College Rd Departamento de Botânica Instituto de Biocências Universidade de São Paulo USP, Rua do Matão, 14 Programa de Pós-Graduação em Genética e Biologia Molecular Centro de Biologia Molecular e Engenharia Genética Instituto de Biologia Universidade Estadual de Campinas Avenida Cândido Rondon Cidade Universitária Departamento de Biodiversidade Instituto de Biociências Universidade Estadual Paulista UNESP, Av. 24-A, 1515 Programa de Pós-Graduação em Biologia Vegetal Departamento de Biodiversidade Instituto de Biociências Universidade Estadual Paulista UNESP, Av. 24-A, 1515 Departamento de Biodiversidade Instituto de Biociências Universidade Estadual Paulista UNESP, Av. 24-A, 1515

Made available in DSpace on 2020-12-12T02:19:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-01 Many studies ask how aluminum (Al) reduces the root growth, but as Al is mostly retained in the root system, physiological explanations for the also expected Al-induced decrease in stomatal conductance (gs) are unclear, mainly in well-watered conditions. We exposed tomato plants (Solanum lycopersicum) to 0, 25, 50 and 100 μM Al in nutrient solution to investigate whether Al impairs root hydraulic conductance (Lpr), affecting leaf water potential (Ψleaf) and possibly inducing abscisic acid (ABA) accumulation in roots and/or leaves. We also measured ABA delivery rate, xylem sap pH and the root/leaf area ratio in order to explain the low gs in plants exposed to Al. Declines in Lpr and gs were proportional to the increase in Al concentration, and all Al treatments similarly decreased Ψleaf, indicating the plant's attempt to reduce water loss through transpiration while accumulating more ABA. Despite Al-induced increases in root ABA, the root-to-shoot delivery of ABA did not enhance, but Al caused root xylem sap alkalization. Despite the stability of root/leaf area ratio across a range of Al concentrations (0, 25 and 50 μM Al), the leaf hydration and stomatal opening was not conserved. Here we provide the first evidence that decreases in Lpr and increases in ABA might explain Al-induced stomatal closure. Programa de Pós-Graduação em Biologia Vegetal Departamento de Biodiversidade Instituto de Biociências Universidade Estadual Paulista UNESP, Av. 24-A Lancaster Environment Centre Lancaster University Lancaster University, Library Avenue, Lancaster Departamento de Biologia Aplicada à Agropecuária Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista UNESP, Via de Acesso Professor Paulo Donato Castelane Castellane S/N - Vila Industrial Departamento de Biodiversidade Instituto de Biociências Universidade Estadual Paulista UNESP, Av. 24-A, 1515 Programa de Pós-Graduação em Biologia Vegetal Departamento de Biodiversidade Instituto de Biociências Universidade Estadual Paulista UNESP, Av. 24-A Departamento de Biologia Aplicada à Agropecuária Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista UNESP, Via de Acesso Professor Paulo Donato Castelane Castellane S/N - Vila Industrial Departamento de Biodiversidade Instituto de Biociências Universidade Estadual Paulista UNESP, Av. 24-A, 1515

Made available in DSpace on 2015-08-26T19:22:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2015. Added 1 bitstream(s) on 2015-08-31T13:03:57Z : No. of bitstreams: 1 S0001-37652015005040332.pdf: 687363 bytes, checksum: 7dffe228848f6596d26d83857a49793c (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) No presente trabalho nós investigamos como o pré-tratamento com auxina, citocinina, giberelina, ácido abscísico e etileno alteram as respostas fisiológicas de sementes de feijão guandu germinadas em água e sob estresse causado por excesso de cádmio. As sementes tratadas com água ou não-tratadas foram utilizadas como controle. Quando comparadas às sementes não tratadas, percebemos que os pré-tratamentos hormonais resultaram em um aumento na germinação do feijão guandu na condição de estresse. Entretanto, esses tratamentos não diferiram daqueles apenas com água. Nós também observamos uma tendência de tolerância aos efeitos do cádmio na presença de etileno, sugerindo que o uso desse hormônio possa ser um método eficiente para superar o efeito do estresse por cádmio durante a germinação de sementes. In this work we investigated whether priming with auxin, cytokinin, gibberellin, abscisic acid and ethylene, alters the physiological responses of seeds of pigeon pea germinated under water and cadmium stress. Seeds treated with water or non-treated seeds were used as control. Although compared to non-treated seeds we found that the hormone treatments improve the germination of pigeon pea under cadmium stress, however, these treatments did not differ from water. However, we also observed a trend of tolerance to the effects of cadmium in the presence of ethylene, suggesting that the use of this hormone may be an efficient method to overcome seed germination under metal stress. Universidade Estadual Paulista Júlio de Mesquita Filho Departamento de Biologia Aplicada à Agropecuária Michigan State University Department of Energy-Plant Research Laboratory Universidade Estadual Paulista Júlio de Mesquita Filho Departamento de Biologia Aplicada à Agropecuária, Jaboticabal

Made available in DSpace on 2018-11-26T17:34:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-08-19 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Phytochromes are the best characterized and most frequently studied plant photoreceptors. A plethora of studies have revealed important roles for phytochromes in plant development, and more recently, evidence indicates that these photoreceptors also modulate responses to a multitude of abiotic and biotic stresses. Thus, the present work aimed to investigate whether tomato phytochromes phyA, phyB1 and phyB2 are involved with responses to low water potential (polyethylene glycol 6000 at Psi(W) of -0.3 MPa), high salinity (100 mM NaC1), cadmium contamination (65 mM CdCl2), high temperature (42 degrees C for six hours during three days) and ultraviolet B radiation (UV-B - 280-320 urn for eight hours during three days) stresses. For this purpose, seedlings of tomato mutants impacted by phytochrome A (fri), phytochrome B1 (tri) and phytochrome B2 (phyB2) were subjected to abiotic stresses and evaluated for their growth, pigment and osmoprotectant accumulation and lipid peroxidation. Under the conditions of this study, the results did not shown large variations of phyA mutant when compared to the wild genotype. However, the tomato phytochromes B1 and B2 mainly act as negative regulators of growth, pigment maintenance and osmoprotectant accumulation during responses to the different abiotic stresses. Univ Estadual Paulista, FCAV, DBAA, UNESP, BR-14884900 Jaboticabal, SP, Brazil Univ Brasilia, Inst Ciencias Biol, Dept Bot, UnB, BR-70910900 Brasilia, DF, Brazil Univ Fed Goias, Inst Ciencias Biol, Dept Bot, BR-74001970 Goiania, Go, Brazil Univ Estadual Paulista, FCAV, DBAA, UNESP, BR-14884900 Jaboticabal, SP, Brazil

Separately, it is well-documented that phytochromes (phys), gibberellin (GA) and abscisic acid (ABA) strongly control the seed germination in tomato. However, we hipothesized that phys inte- ract with GA or ABA during this response. Thus, we make an analysis of seed germination of ABA deficient (sit), GA constitutive response (pro), phytochrome deficient (au) mutants as well as, spe- cially, au sit and au pro double mutants of tomato incubated in the dark or light conditions during 120 h (12 h intervals (i)). Compared to au, which severely reduced percentage germination (Gi%) and pro, which did not alter Gi%, au pro showed in the light enhanced Gi% and germination speed index (GSI) besides the reduced average germination time (AGT). Moreover, in the dark, germina- tion of au pro was similar to pro. These results indicate that the mechanisms by which GA mod- ulate germination in tomato are light dependent through the phy signaling, whereas intermediary values of Gi%, GSI and AGT in dark and light of au sit compared to au and sit single mutants indi- cate an additive effect of the au and sit mutations, suggesting that ABA and phy may act through the parallel signaling pathway.

Made available in DSpace on 2022-04-28T19:03:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-03-01 The far red light insensitive (fri) mutant of tomato, which is phytochrome A (phyA) deficient, displays some characteristics that have recently indicated important functions of this photoreceptor in water relations. With respect to the relationship between nutrition and water relations, we investigated the growth and nutritional status of fri supplied with Hoagland's complete solution and solutions with the individual omission of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S). For this purpose, 20-day-old tomato plants of the WT (cv. Moneymaker) and fri mutant were transplanted into pots (one plant per pot) that contained Hoagland and Arnon (1950) solution diluted to 50 per cent in the first week and to 100 per cent from the second week of cultivation until the end of the experiment (50 DAT). Seven treatments were performed: a complete nutrient solution (KH2PO4, KNO3, Ca(NO3)2.5H2O, MgSO4.7H2O, KCl, CaCl2, H3BO3, MnCl2.4H2O, ZnCl2, CuCl2, H2MoO4H2O and Fe EDTA) and the individual omission N (KNO3, Ca(NO3)2.5H2O); P (KH2PO4); K (KH2PO4, KNO3); Ca (CaCl2); Mg and S (MgSO4.7H2O) from a balanced nutrient solution. The experiment was arranged in a completely randomized factorial design with two genotypes and seven types of nutrient solutions with three replications. Upon harvest, the following measurements were performed: the height of the plants, measured from the base of the stem of each plant to the insertion of the first fully expanded leaf; the stem diameter; the total number of leaves per plant; an indirect chlorophyll measurement, which we called the green color index, and the leaf area. Statistical analysis was performed using analysis of variance (ANOVA) followed by Tukey's test. First, based on growth analyses, fri showed an enhanced dry weight of the shoot, root and whole plant in complete solution compared with the wild type (WT). In addition, the phyA mutant had a multifaceted response compared with that of the WT when the nutrients were omitted. For the fri mutant, the height and green color index were reduced without N and K; the leaf area without P, K and S; the dry weight of the root and shoot without N, P, K and S, and the root, shoot and total plant dry weight without P, K and S. On the other hand, the green color index of the fri mutant was enhanced without Ca and Mg. Together, these results show that in addition to revealing an altered response to nutrition in the fri mutant, phyA can play a role in light signaling in the nutrition and nutritional stress of tomato. Department of Biology Applied to Agriculture São Paulo State University, Via de Acesso Prof. Paulo Donato Castellane s/n Department of Soil and Fertilizer São Paulo State University, Via de Acesso Prof. Paulo Donato Castellane s/n Department of Biology Applied to Agriculture São Paulo State University, Via de Acesso Prof. Paulo Donato Castellane s/n Department of Soil and Fertilizer São Paulo State University, Via de Acesso Prof. Paulo Donato Castellane s/n

Made available in DSpace on 2022-04-28T19:01:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-01-01 Phytochromes are red/far-red light photoreceptors that mediate a variety of photomorphogenic processes in plants, from germination to flowering. In addition, there is evidence that phytochromes are also part of the stress signalling response, especially in response to water deficit stress, which is the major abiotic factor limiting plant growth and crop productivity worldwide. In this study, we used the phyA (far red-insensitive; fri), phyB1 (temporary red-insensitive; tri) and phyB2 mutants of tomato (Solanum lycopersicum L.) to study the roles of these three phytochromes in drought stress responses. Compared to wild type (WT) plants grown under water-deficit stress conditions, the fri, tri, and phyB2 mutants did not exhibit altered dry weights, leaf areas, stomatal densities, or stomatal opening. The stomatal conductance of all three mutants was severely reduced under both fully-hydrated and water-deficit conditions. Although relative water contents did change after drought stress in each mutant, the most significant reduction in water potential during water stress was observed in the fri mutant. However, this mutant returned its water status to WT levels during rehydration. Although the phyB2 mutant lost more water from detached leaves during abscisic acid (ABA) treatment, phyB2 behaved like WT plants, indicating that this mutant was not insensitive to ABA. Overall, these results indicate that the phytochromes phyA, phyB1, and phyB2 modulate drought stress responses in tomato. Departamento de Biologia Aplicada à Agropecuária Universidade Estadual Paulista “Júlio de Mesquita Filho”, Via de Acesso Prof. Paulo Donato Castellane s/n Departamento de Biologia Geral Universidade Federal de Goiás, Km 13 Departamento de Biologia Aplicada à Agropecuária Universidade Estadual Paulista “Júlio de Mesquita Filho”, Via de Acesso Prof. Paulo Donato Castellane s/n