Photosynthetic capacity and water use efficiency in sugarcane genotypes subject to water deficit during early growth phase

The objective of this study was to compare the gas exchange, photosynthetic capacity and water potential of sugarcane genotypes cultivated under water deficit conditions imposed during the initial growth phase. Experiments were performed in a greenhouse using two sugarcane genotypes namely: HoCP93-776 (drought susceptible) and TCP02-4587 (drought tolerant). Sixty days after planting, two different water treatments were applied (i.e., with or without water deficit). At 0,30 and 60 days after the treatment, gas exchange variables were evaluated for their relationship with water use, intrinsic instantaneous water use efficiency and instantaneous carboxylation efficiency. The SPAD index, photosynthetic pigments, water potential and relative water content in the leaves were also analyzed. The genotype HoCP93-776 was more sensitive to drought treatment as indicated by the significantly lower values of SPAD index, photosynthetic pigments, water potential (Ψw) and relative water content (RWC) variables. The genotype TCP02-4587 had higher water potential, stomatal control efficiency, water use efficiency (WUE), intrinsic instantaneous water use efficiency (WUEintr), instantaneous carboxylation efficiency and photosynthetic capacity. The highest air vapor pressure deficit during the drought conditions could be due to the stomatal closing in the HoCP93-776, which contributed to its lower photosynthetic capacity.

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.

Measured and modeled interactive effects of potassium deficiency and water deficit on gross primary productivity and light-use efficiency in Eucalyptus grandis plantations

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Leaf paraheliotropism in Styrax camporum confers increased light use efficiency and advantageous photosynthetic responses rather than photoprotection

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

Nutrition, dry matter accumulation and partitioning and phosphorus use efficiency of potato grown at different phosphorus levels in nutrient solution

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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.

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)

Comparative gas exchange performance during the wet season of three Brazilian Styrax species under habitat conditions of cerrado vegetation types differing in soil water availability and crown density

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

Effects of soil water deficit and nitrogen nutrition on water relations and photosynthesis of pot-grown Coffea canephora Pierre

Coffea canephora plants (clone INCAPER-99) were submitted to low N (LN) or high N (HN) applications and two watering regimes (daily irrigation and irrigation every 5 days for a month). Although water potential was not altered significantly by N, HN plants showed higher relative water content than did LN plants under water deficit. Only HN plants exhibited some ability for osmotic adjustment. Plants from both N treatments increased their cell wall rigidity under drought, with a more pronounced augmentation in HN plants. In well-watered plants, carbon assimilation rate increased with increasing N while stomatal conductance did not respond to N supply. Under drought conditions, carbon assimilation decreased by 68-80% compared to well-watered plants, whereas stomatal conductance and transpiration rate declined by 35% irrespective of the N applications. Stable carbon isotope analysis, combined with leaf gas exchange measurements, indicated that regardless of the watering treatments, N increased the long-term water use efficiency through changes in carbon assimilation with little or no effect on stomatal behaviour.

Effect of plant density on Stevia rebaudiana Bertoni water consumption

Stevia rebaudiana is a traditional crop of Latin America, now rising to international interest thanks to its specific glycosides that are very sweet and still poor of calories making its potential interesting for dietary recommendations. Its short growing cycle makes this species possible as an annual crop also in non tropical areas, including the Mediterranean Basin and parts of Italy, where rainfall or irrigation is available during late spring and summer. One of the main concerns is the quantity of water necessary for the crop and the ideal number of plants per hectare in order to maximize water use efficiency. The present research was carried out in central Italy to compare yields and water consumption in plots with three plant densities (50, 25, 16 plants per square metre). The results show that the most dense plots can give the best results in the area of the trial.

Intercropping soybean and palisade grass for enhanced land use efficiency and revenue in a no till system

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

Water use of Juniperus virginiana trees encroached into mesic prairies in Oklahoma, USA

Juniperus virginiana (eastern redcedar) is encroaching into mesic prairies of the southern Great Plains, USA, and is altering the hydrologic cycle. We used the thermal dissipation technique to quantify daily water use of J. virginiana into a mesic prairie by measuring 19 trees of different sizes from different density stands located in north-central Oklahoma during 2011. We took the additional step to calibrate our measurements by comparing thermal dissipation technique estimates to volumetric water use for a subset of trees. Except for days with maximum air temperature below -3 degrees C, J. virginiana trees used water year round, reached a peak in late May, and exhibited reduced water use in summer when soil water availability was low. Overall daily average water use was 24 l (+/- 21.81 s.d.) per tree. Trees in low density stands used more water than trees with similar diameters from denser stands. However, there was no difference in water use between trees in different density stands when expressed on a canopy area basis. Approximately 50% of variation in water use that remained after accounting for the factors site, tree, and day was explained using a physiologically-based model that included daily potential evapotranspiration, maximum vapour pressure deficit, maximum temperature, solar radiation, and soil water storage between 0 and 10 cm. Our model suggested that a J. virginiana woodland with a closed canopy is capable of transpiring almost all precipitation reaching the soil in years with normal precipitation, indicating the potential for encroachment to reduce water yield for streamflow and groundwater recharge. Copyright (C) 2013 John Wiley & Sons, Ltd.

Overexpression of the activated form of the AtAREB1 gene (AtAREB1 Delta QT) improves soybean responses to water deficit

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The use of grafting to improve the net photosynthesis of cucumber

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

Manejo da irrigação na cultura do feijoeiro em sistemas plantio direto e convencional

O manejo inadequado do solo e da água é limitante à produtividade do feijoeiro irrigado. O objetivo deste trabalho foi avaliar dois métodos de manejo da irrigação, um via solo (tensiometria) e outro via clima (tanque Classe A), conjugados com os sistemas plantio direto e convencional de manejo do solo com a cultura do feijoeiro de inverno, no segundo ano de plantio direto, em Jaboticabal - SP. Foi medido o potencial mátrico do solo e estimada a variação diária do armazenamento de água no solo, na camada de 0 a 0,40 m de profundidade, e avaliados os componentes de produtividade, além de determinadas a evapotranspiração real média e a eficiência média de uso de água pela cultura. O sistema de preparo convencional do solo com manejo de irrigação pelo tanque Classe A proporcionou maior produtividade de grãos, evapotranspiração média e eficiência de uso de água pela cultura, seguido pelo plantio direto com manejo de irrigação por tensiometria e por tanque Classe A. O sistema plantio direto foi menos suscetível às variações hídricas no solo decorrentes dos manejos de irrigação empregados do que o sistema de preparo convencional, resultando em menor variação na produtividade de grãos.