Nitrogen sources and CO2 concentration synergistically affect the growth and metabolism of tobacco plants.

The initial stimulation of photosynthesis under elevated CO2 concentrations (eCO2) is often followed by a decline in photosynthesis, known as CO2 acclimation. Changes in N levels under eCO2 can have different effects in plants fertilized with nitrate (NO3-) or ammonium (NH4+) as the N source. NO3- assimilation consumes approximately 25% of the energy produced by an expanded leaf, whereas NH4+ requires less energy to be incorporated into organic compounds. Although plant-N interactions are important for the productivity and nutritional value of food crops worldwide, most studies have not compared the performance of plants supplied with different forms of N. Therefore, this study aims to go beyond treating N as the total N in the soil or the plant because the specific N compounds formed from the available N forms become highly engaged in all aspects of plant metabolism. To this end, plant N metabolism was analyzed through an experiment with eCO2 and fertigation with NO3- and/or NH4+ as N sources for tobacco (Nicotiana tabacum) plants. The results showed that the plants that received only NO3- as a source of N grew more slowly when exposed to a CO2 concentration of 760 µmol mol-1 than when they were exposed to ambient CO2 conditions. On the other hand, in plants fertigated with only NH4+, eCO2 enhanced photosynthesis. This was essential for the maintenance of the metabolic pathways responsible for N assimilation and distribution in growing tissues. These data show that the physiological performance of tobacco plants exposed to eCO2 depends on the form of inorganic N that is absorbed and assimilated.

Structural and functional changes in coffee trees after 4 years under free air CO2 enrichment.

Background and Aims: Climate forecasts suggest that [CO2] in the atmosphere will continue to increase. Structural and ecophysiological responses to elevated air [CO2] (e[CO2]) in tree species are contradictory due to species-dependent responses and relatively short-term experiments. It was hypothesized that long-term exposure (4 year) to e[CO2] would change canopy structure and function of Coffea arabica trees. Methods: Coffee plants were grown in a FACE (free air CO2 enrichment) facility under two air [CO2]: actual and elevated (actual + approx. 200 µL CO2 L-1). Plants were codified following the VPlants methodology to obtain coffee mock-ups. Plant canopies were separated into three 50 cm thick layers over a vertical profile to evaluate their structure and photosynthesis, using functional-structural plant modelling. Key Results: Leaf area was strongly reduced on the bottom and upper canopy layers, and increased soil carbon concentration suggested changes in carbon partitioning of coffee trees under e[CO2]. Increased air [CO2] stimulated stomatal conductance and leaf photosynthesis at the middle and upper canopy layers, increasing water-use efficiency. Under e[CO2], plants showed reduced diameter of the second-order axes and higher investment in the youngest third to fifth-order axes. Conclusions: The responses of Arabica coffee grown under long-term exposure to e[CO2] integrated structural and functional modifications, which balanced leaf area loss through improvements in leaf and whole-plant photosynthesis.

Diagnostic accuracy of concentric needle jitter in myasthenia: Prospective study.

INTRODUCTION: The aim of this study was to estimate jitter parameters in the orbicularis oculi muscle using a concentric needle electrode (CNE) in patients with myasthenia gravis (MG) and to determine its diagnostic accuracy for jitter analysis (CNEMG-jitter). METHODS: CNEMG-jitter was performed in 20 healthy subjects and 33 MG patients using the voluntary contraction technique. Receiver operating characteristic (ROC) curves were constructed to determine cut-off points with the best sensitivity/specificity combination for jitter analysis. RESULTS: CNEMG-jitter yielded high positivity rates for ocular MG (92.3%) and generalized MG (100%). The ROC curve cut-off point that provided the highest sensitivity without false positives was 24.7 µs for mean jitter and 33.1 µs for the 18th highest value. Sensitivity was 93.9% for both parameters. Diagnostic accuracy of CNEMG-jitter was > 96%. CONCLUSIONS: CNEMG-jitter yielded high sensitivity and specificity rates. Our reference values were lower than previously published values, possibly due to less technical variation between the different recordings. Muscle Nerve 55: 190-194, 2017.

Voiding dysfunction in patients with neuromyelitis optica spectrum disorders.

AIMS: We assessed the lower urinary tract symptoms (LUTS) and urodynamic findings in patients with neuromyelitis optica spectrum disorders (NMO-SD), a recently defined neurological disease. METHODS: We prospectively evaluated seven men and 23 women (mean age 41.1 ± 13.5 years) with an established diagnosis of NMO-SD who were invited to participate irrespective of the presence of LUTS. Neurological evaluation was assessed with the Expanded Disability Status Scale (EDSS) and LUTS were evaluated with the Overactive Bladder questionnaire (OAB-V8) and the International Prostate Symptom Score (I-PSS). All patients underwent videourodynamics, transabdominal urinary tract sonography, urine culture, and serum creatinine levels. RESULTS: The mean time of disease duration was 33.8 ± 30.8 months. Neurological evaluation showed a mean EDSS score of 5.3 ± 1.8. The most frequent videourodynamic findings were detrusor-sphincter dyssynergia (DSD) and detrusor overactivity (DO) in 11 (36.6%) patients, DSD without DO in seven (23.3%) and DO without DSD in six (20.0%) patients. Voiding dysfunction assessed by I-PSS and OAB-V8 increased with the degree of neurological impairment (P = 0.018; r = 0.42 and P = 0.006; r = 0.48 respectively). Patients with DSD had higher I-PSS (18.5 ± 11.4 vs 7.0 ± 9.2; P = 0.029) and OAB-V8 scores (22.8 ± 15.8vs 9.1 ± 7.8; P = 0.008), and worse neurological impairment (mean EDSS 5.9 ± 1.8 vs 4.5 ± 1.5; P = 0.027). CONCLUSIONS: Most patients with NMO-SD have LUTS and voiding dysfunction, with DSD and DO as the main urodynamic findings. The severity of the neurological disease is a predictive factor for the occurrence of voiding dysfunction and detrusor-sphincter dyssynergia.

Physiological and transcriptional analyses of developmental stages along sugarcane leaf.

BACKGROUND: Sugarcane is one of the major crops worldwide. It is cultivated in over 100 countries on 22 million ha. The complex genetic architecture and the lack of a complete genomic sequence in sugarcane hamper the adoption of molecular approaches to study its physiology and to develop new varieties. Investments on the development of new sugarcane varieties have been made to maximize sucrose yield, a trait dependent on photosynthetic capacity. However, detailed studies on sugarcane leaves are scarce. In this work, we report the first molecular and physiological characterization of events taking place along a leaf developmental gradient in sugarcane. RESULTS: Photosynthetic response to CO2 indicated divergence in photosynthetic capacity based on PEPcase activity, corroborated by activity quantification (both in vivo and in vitro) and distinct levels of carbon discrimination on different segments along leaf length. Additionally, leaf segments had contrasting amount of chlorophyll, nitrogen and sugars. RNA-Seq data indicated a plethora of biochemical pathways differentially expressed along the leaf. Some transcription factors families were enriched on each segment and their putative functions corroborate with the distinct developmental stages. Several genes with higher expression in the middle segment, the one with the highest photosynthetic rates, were identified and their role in sugarcane productivity is discussed. Interestingly, sugarcane leaf segments had a different transcriptional behavior compared to previously published data from maize. CONCLUSION: This is the first report of leaf developmental analysis in sugarcane. Our data on sugarcane is another source of information for further studies aiming to understand and/or improve C4 photosynthesis. The segments used in this work were distinct in their physiological status allowing deeper molecular analysis. Although limited in some aspects, the comparison to maize indicates that all data acquired on one C4 species cannot always be easily extrapolated to other species. However, our data indicates that some transcriptional factors were segment-specific and the sugarcane leaf undergoes through the process of suberizarion, photosynthesis establishment and senescence.

Existence of a potential neurogenic system in the adult human brain.

BACKGROUND: Prevailingly, adult mammalian neurogenesis is thought to occur in discrete, separate locations known as neurogenic niches that are best characterized in the subgranular zone (SGZ) of the dentate gyrus and in the subventricular zone (SVZ). The existence of adult human neurogenic niches is controversial. METHODS: The existence of neurogenic niches was investigated with neurogenesis marker immunostaining in histologically normal human brains obtained from autopsies. Twenty-eight adult temporal lobes, specimens from limbic structures and the hypothalamus of one newborn and one adult were examined. RESULTS: The neural stem cell marker nestin stained circumventricular organ cells and the immature neuronal marker doublecortin (DCX) stained hypothalamic and limbic structures adjacent to circumventricular organs; both markers stained a continuous structure running from the hypothalamus to the hippocampus. The cell proliferation marker Ki-67 was detected predominantly in structures that form the septo-hypothalamic continuum. Nestin-expressing cells were located in the fimbria-fornix at the insertion of the choroid plexus; ependymal cells in this structure expressed the putative neural stem cell marker CD133. From the choroidal fissure in the temporal lobe, a nestin-positive cell layer spread throughout the SVZ and subpial zone. In the subpial zone, a branch of this layer reached the hippocampal sulcus and ended in the SGZ (principally in the newborn) and in the subiculum (principally in the adults). Another branch of the nestin-positive cell layer in the subpial zone returned to the optic chiasm. DCX staining was detected in the periventricular and middle hypothalamus and more densely from the mammillary body to the subiculum through the fimbria-fornix, thus running through the principal neuronal pathway from the hippocampus to the hypothalamus. The column of the fornix forms part of this pathway and appears to coincide with the zone previously identified as the human rostral migratory stream. Partial co-labeling with DCX and the neuronal marker ßIII-tubulin was also observed. CONCLUSIONS: Collectively, these findings suggest the existence of an adult human neurogenic system that rises from the circumventricular organs and follows, at minimum, the circuitry of the hypothalamus and limbic system.

New Perspective on the Use of α-Bisabolol for Weed Control.

The indiscriminate use of synthetic herbicides reduces its effectiveness. Bioherbicides produced with metabolites emerge as an alternative to managing weeds. We aimed to analyze the phytotoxic potential of the essential oil of Vanillosmopsis arborea (EOVA) and the α-bisabolol molecule, its main component. We evaluated the effects of EOVA and α-bisabolol at different concentrations on the germination, growth, antioxidant metabolism, and photosynthesis of different species. EOVA and α-bisabolol showed promising phytotoxic effects on the germination and initial growth of the weed Senna occidentalis, inhibiting the activity of the antioxidant enzymes and increasing lipid peroxidation. α-Bisabolol reduced the weed seedling growth by inducing oxidative stress, which suggests a greater role in postemergence. Moreover, in the weed postemergence, both EOVA and α-bisabolol caused damage in the shoots, reduced the chlorophyll content, and increased lipid peroxidation besides reducing photosynthesis in S. occidentalis. Overall, we suggest the promising action of α-bisabolol and EOVA as bioherbicides for weed control.

Soybean Plants Exposed to Low Concentrations of Potassium Iodide Have Better Tolerance to Water Deficit through the Antioxidant Enzymatic System and Photosynthesis Modulation.

Water deficit inhibits plant growth by affecting several physiological processes, which leads to the overproduction of reactive oxygen species (ROS) that may cause oxidative stress. In this regard, iodine (I) is already known to possibly enhance the antioxidant defense system of plants and promote photosynthetic improvements under adverse conditions. However, its direct effect on water deficit responses has not yet been demonstrated. To verify the efficiency of I concerning plant tolerance to water deficit, we exposed soybean plants to different concentrations of potassium iodide (KI) fed to pots with a nutrient solution and subsequently submitted them to water deficit. A decline in biomass accumulation was observed in plants under water deficit, while exposure to KI (10 and 20 µmol L-1) increased plant biomass by an average of 40%. Furthermore, exposure to KI concentrations of up to 20 µM improved gas exchange (~71%) and reduced lipid peroxidation. This is related to the higher enzymatic antioxidant activities found at 10 and 20 µM KI concentrations. However, when soybean plants were properly irrigated, KI concentrations greater than 10 µM promoted negative changes in photosynthetic efficiency, as well as in biomass accumulation and partition. In sum, exposure of soybean plants to 10 µM KI improved tolerance to water deficit, and up to this concentration, there is no evidence of phytotoxicity in plants grown under adequate irrigation.

KI Increases Tomato Fruit Quality and Water Deficit Tolerance by Improving Antioxidant Enzyme Activity and Amino Acid Accumulation: A Priming Effect or Relief during Stress?

A water deficit can negatively impact fruit yield and quality, affecting critical physiological processes. Strategies to mitigate water deficits are crucial to global food security. Iodine (I) may increase the efficiency of the antioxidant system of plants, but its role against water deficits is poorly understood. This study aimed to evaluate the effectiveness of I in attenuating water deficits and improving fruit quality, investigating whether metabolic responses are derived from a "priming effect" or stress relief during water deficits. Tomato plants were exposed to different concentrations of potassium iodide (KI) via a nutrient solution and subjected to a water deficit. A water deficit in tomatoes without KI reduced their yield by 98%. However, a concentration of 100 µM of KI increased the yield under a water deficit by 28%. This condition is correlated with increased antioxidant activity, photosynthetic efficiency improvement, and malondialdehyde reduction. In addition, the concentration of 100 µM of KI promoted better fruit quality through antioxidant capacity and a decline in the maturation index. Therefore, KI can be an alternative for attenuating water deficits in tomatoes, inducing positive responses during the water deficit period while at the same time improving fruit quality.

Interhemispheric asymmetry of corticomotor excitability after chronic cerebellar infarcts.

Early after stroke, there is loss of intracortical facilitation (ICF) and increase in short-interval intracortical inhibition (SICI) in the primary motor cortex (M1) contralateral to a cerebellar infarct. Our goal was to investigate intracortical M1 function in the chronic stage following cerebellar infarcts (>4 months). We measured resting motor threshold (rMT), SICI, ICF, and ratios between motor-evoked potential amplitudes (MEP) and supramaximal M response amplitudes (MEP/M; %), after transcranial magnetic stimulation was applied to the M1 contralateral (M1(contralesional)) and ipsilateral (M1(ipsilesional)) to the cerebellar infarct in patients and to both M1s of healthy age-matched volunteers. SICI was decreased in M1(contralesional) compared to M1(ipsilesional) in the patient group in the absence of side-to-side differences in controls. There were no significant interhemispheric or between-group differences in rMT, ICF, or MEP/M (%). Our results document disinhibition of M1(contralesional) in the chronic phase after cerebellar stroke.

[Stroke in a neurology ward: etiologies, complications and length of stay]. / Acidente vascular cerebral isquêmico em uma enfermaria de neurologia: complicações e tempo de internação.

INTRODUCTION: Purposes of this study were: evaluate complications and length of stay of patients admitted with diagnosis of ischemic stroke (IS) in the acute or subacute phase, in a general Neurology ward in São paulo, Brazil; investigate the influence of age, risk factors for vascular disease, arterial territory and etiology. METHODS: Data from 191 IS patients were collected prospectively. RESULTS: Fifty-one patients (26.7%) presented at least one clinical complication during stay. pneumonia was the most frequent complication. Mean length of stay was 16.8+-13.8 days. Multivariate analysis revealed a correlation between younger age and lower complication rates (OR=0.92-0.97, p < 0.001). presence of complications was the only factor that independently influenced length of stay (OR=4.20; CI=1.928.84; p<0.0001). CONCLUSION: These results should be considered in the planning and organization of IS care in Brazil.

Biomass Accumulation and Cell Wall Structure of Rice Plants Overexpressing a Dirigent-Jacalin of Sugarcane (ShDJ) Under Varying Conditions of Water Availability.

A sugarcane gene encoding a dirigent-jacalin, ShDJ, was induced under drought stress. To elucidate its biological function, we integrated a ShDJ-overexpression construction into the rice Nipponbare genome via Agrobacterium-mediated transformation. Two transgenic lines with a single copy gene in T0 were selected and evaluated in both the T1 and T4 generations. Transgenic lines had drastically improved survival rate under water deficit conditions, at rates close to 100%, while WT did not survive. Besides, transgenic lines had improved biomass production and higher tillering under water deficit conditions compared with WT plants. Reduced pectin and hemicellulose contents were observed in transgenic lines compared with wild-type plants under both well-watered and water deficit conditions, whereas cellulose content was unchanged in line #17 and reduced in line #29 under conditions of low water availability. Changes in lignin content under water deficit were only observed in line #17. However, improvements in saccharification were found in both transgenic lines along with changes in the expression of OsNTS1/2 and OsMYB58/63 secondary cell wall biosynthesis genes. ShDJ-overexpression up-regulated the expression of the OsbZIP23, OsGRAS23, OsP5CS, and OsLea3 genes in rice stems under well-watered conditions. Taken together, our data suggest that ShDJ has the potential for improving drought tolerance, plant biomass accumulation, and saccharification efficiency.

Seroprevalence of NMO-IgG antibody in Brazilian patients with neuromyelitis optica.

OBJECTIVE: To determine the seroprevalence of neuromyelitis optica antibody (NMO)-IgG in Brazilian patients with clinical diagnosis of relapsing neuromyelitis optica, also known as Devic's disease. METHOD: We determined NMO-IgG titers in 28 patients (25 of them females) that fulfilled the 1999 NMO diagnostic criteria proposed by Wingerchuk et al. RESULTS: NMO-IgG was detected in 18 NMO patients (64.3%). CONCLUSION: Our results showed that seroprevalence of NMO-IgG in Brazilian NMO patients was similar to the observed in other studies.

Stroke management in a university hospital in the largest South American city.

OBJECTIVE: To describe characteristics and provision of care for patients admitted with cerebrovascular disorders (CVD), focusing on ischemic stroke (IS), in a large, public, academic hospital in São Paulo, Brazil. METHOD: We retrieved information about 357 patients with CVD admitted to the Neurology Emergency Department (NED) and Neurology Ward (NW) of our institution. We described patient characteristics and management of IS in NED and in NW. RESULTS: IS was diagnosed in 79.6% of CVD patients admitted to NED; 2.7% were submitted to thrombolysis. Extent of IS investigation and management were significantly different in NED and NW. CONCLUSION: IS patients in our center were younger than in developed countries. IS management was significantly influenced by patient characteristics. This information can aid in planning strategies to decrease stroke burden.

Drought tolerance of sugarcane propagules is improved when origin material faces water deficit.

Drought stress can imprint marks in plants after a previous exposure, leading to plant acclimation and a permissive state that facilitates a more effective response to subsequent stress events. Such stress imprints would benefit plants obtained through vegetative propagation (propagules). Herein, our hypothesis was that the propagules obtained from plants previously exposed to water deficit would perform better under water deficit as compared to those obtained from plants that did not face stressful conditions. Sugarcane plants were grown under well-hydrated conditions or subjected to three cycles of water deficit by water withholding. Then, the propagules were subjected to water deficit. Leaf gas exchange was reduced under water deficit and the propagules from plants that experienced water deficit presented a faster recovery of CO2 assimilation and higher instantaneous carboxylation efficiency after rehydration as compared to the propagules from plants that never faced water deficit. The propagules from plants that faced water deficit also showed the highest leaf proline concentration under water deficit as well as higher leaf H2O2 concentration and leaf ascorbate peroxidase activity regardless of water regime. Under well-watered conditions, the propagules from plants that faced stressful conditions presented higher root H2O2 concentration and higher activity of catalase in roots as compared to the ones from plants that did not experience water shortage. Such physiological changes were associated with improvements in leaf area and shoot and root dry matter accumulation in propagules obtained from stressed plants. Our results suggest that root H2O2 concentration is a chemical signal associated with improved sugarcane performance under water deficit. Taken together, our findings bring a new perspective to the sugarcane production systems, in which plant acclimation can be explored for improving drought tolerance in rainfed areas.

Clinical variability of early-onset congenital myasthenic syndrome due to biallelic RAPSN mutations in Brazil.

Mutations in RAPSN are an important cause of congenital myasthenic syndrome (CMS), leading to endplate acetylcholine receptor deficiency. We present three RAPSN early-onset CMS patients (from a Brazilian cohort of 61 CMS patients). Patient 1 and patient 2 harbor the mutation p.N88K in homozygosity, while patient 3 harbors p.N88K in compound heterozygosity with another pathogenic variant (p.V165M; c.493G ≥ A). At onset, patient 3 presented with more severe symptoms compared to the other two, showing generalized weakness and repeated episodes of respiratory failure in the first years of life. During adolescence, she became gradually less symptomatic and does not require medication anymore, presenting better long-term outcomes than patients 1 and 2. This case series illustrates the variability of RAPSN early-onset CMS, with patient 3, despite severe onset, revealing an almost complete reversal of myasthenic symptoms, not limited to apneic episodes. Moreover, it suggests that RAPSN CMS may be underdiagnosed in non-European countries.

Drought tolerance of sugarcane is improved by previous exposure to water deficit.

Under field conditions, plants are exposed to cycles of dehydration and rehydration during their lifespan. In this study, we hypothesized that sugarcane plants previously exposed to cycles of water deficits will perform better than plants that have never faced water deficits when both are subjected to low water availability. Sugarcane plants were grown in a nutrient solution and exposed to one (1WD), two (2WD) or three (3WD) water deficit cycles. As the reference, plants were grown in a nutrient solution without adding polyethylene glycol. Under water deficits, leaf gas exchange was significantly reduced in 1WD and 2WD plants. However, 3WD plants showed similar CO2 assimilation and lower stomatal conductance compared to the reference plants, with increases in intrinsic water-use efficiency. Abscisic acid concentrations were lower in 3WD plants than in 1WD plants. Our data revealed root H2O2 concentration as an important chemical signal, with the highest root H2O2 concentrations found in 3WD plants. These plants presented higher root dry matter and root:shoot ratios compared to the reference plants, as well as higher biomass production when water was available. Our data suggest that sugarcane plants were able to store information from previous stressful events, with plant performance improving under water deficits. In addition, our findings provide a new perspective for increasing drought tolerance in sugarcane plants under nursery conditions.

A common CHRNE mutation in Brazilian patients with congenital myasthenic syndrome.

The most common causes of congenital myasthenic syndromes (CMS) are CHRNE mutations, and some pathogenic allelic variants in this gene are especially frequent in certain ethnic groups. In the southern region of Brazil, a study found the c.130dupG CHRNE mutation in up to 33% of families with CMS. Here, we aimed to verify the frequency of this mutation among individuals with CMS in a larger cohort of CMS patients from different areas of Brazil and to characterize clinical features of these patients. Eighty-four patients with CMS, from 72 families, were clinically evaluated and submitted to direct sequencing of the exon 2 of CHRNE. The c.130dupG mutation was found in 32 patients (23 families), with 26 patients (19 families, 26.3%) in homozygosis, confirming its high prevalence in different regions of Brazil. Among the homozygous patients, the following characteristics were frequent: onset of symptoms before 2 years of age (92.3%), little functional restriction (92.3%), fluctuating symptoms (100%), ocular muscle impairment (96.1%), ptosis (100%), limb weakness (88.4%), response to pyridostigmine (100%), facial involvement (77%), and bulbar symptoms (70.8%). The pretest probability of finding at least one allele harbouring the c.130dupG mutation was 38.1%. Selecting only patients with impaired eye movement together with limb weakness and improvement with pyridostigmine, the probability increases to 72.2%. This clinical pre-selection of patients is likely a useful tool for regions where CHRNE mutations have a founder effect. In conclusion, the CHRNE mutation c.130dupG leads to fairly benign natural course of the disease with relative homogeneity.

Reference genes for normalization of qPCR assays in sugarcane plants under water deficit.

BACKGROUND: Sugarcane (Saccharum spp.) is the main raw material for sugar and ethanol production. Among the abiotic stress, drought is the main one that negatively impact sugarcane yield. Although gene expression analysis through quantitative PCR (qPCR) has increased our knowledge about biological processes related to drought, gene network that mediates sugarcane responses to water deficit remains elusive. In such scenario, validation of reference gene is a major requirement for successful analyzes involving qPCR. RESULTS: In this study, candidate genes were tested for their suitable as reference genes for qPCR analyses in two sugarcane cultivars with varying drought tolerance. Eight candidate reference genes were evaluated in leaves sampled in plants subjected to water deficit in both field and greenhouse conditions. In addition, five genes were evaluated in shoot roots of plants subjected to water deficit by adding PEG8000 to the nutrient solution. NormFinder and RefFinder algorithms were used to identify the most stable gene(s) among genotypes and under different experimental conditions. Both algorithms revealed that in leaf samples, UBQ1 and GAPDH genes were more suitable as reference genes, whereas GAPDH was the best reference one in shoot roots. CONCLUSION: Reference genes suitable for sugarcane under water deficit were identified, which would lead to a more accurate and reliable analysis of qPCR. Thus, results obtained in this study may guide future research on gene expression in sugarcane under varying water conditions.

Physiological Plasticity Is Important for Maintaining Sugarcane Growth under Water Deficit.

The water availability at early phenological stages is critical for crop establishment and sugarcane varieties show differential performance under drought. Herein, we evaluated the relative importance of morphological and physiological plasticity of young sugarcane plants grown under water deficit, testing the hypothesis that high phenotypic plasticity is associated with drought tolerance. IACSP95-5000 is a high yielding genotype and IACSP94-2094 has good performance under water limiting environments. Plants were grown in rhizotrons for 35 days under three water availabilities: high (soil water matric potential [Ψm] higher than -20 kPa); intermediate (Ψm reached -65 and -90 kPa at the end of experimental period) and low (Ψm reached values lower than -150 kPa). Our data revealed that morphological and physiological responses of sugarcane to drought are dependent on genotype and intensity of water deficit. In general, IACSP95-5000 showed higher physiological plasticity given by leaf gas exchange and photochemical traits, whereas IACSP94-2094 showed higher morphological plasticity determined by changes in leaf area (LA) and specific LA. As IACSP94-2094 accumulated less biomass than IACSP95-5000 under varying water availability, it is suggested that high morphological plasticity does not always represent an effective advantage to maintain plant growth under water deficit. In addition, our results revealed that sugarcane varieties face water deficit using distinct strategies based on physiological or morphological changes. When the effectiveness of those changes in maintaining plant growth under low water availability is taken into account, our results indicate that the physiological plasticity is more important than the morphological one in young sugarcane plants.