José C. Ramalho

Impacts of drought and temperature stress on coffee physiology and production: a review

Overall, drought and unfavourable temperatures are the major climatic limitations for coffee production. These limitations are expected to become increasingly important in several coffee growing regions due to the recognized changes in global climate, and also because coffee cultivation has spread towards marginal lands, where water shortage and unfavourable temperatures constitute major constraints to coffee yield. In this review, we examine the impacts of such limitations on the physiology, and consequently on the production of mainly Coffea arabica and C. canephora, which account for about 99 % of the world coffee bean production. The first section deals with climatic factors and the coffee plant’s requirements. The importance of control ling oxidative stress for the expression of drought and cold tolerance abilities is emphasized in the second section. In the third section, we examine the impacts of drought on cell-water relations, stomatal behaviour and water use, photosynthesis and crop yield, carbon and nitrogen metabolism, root growth and characteristics, and on drought tolerance. In the fourth section, the impacts of low positive and high temperatures on coffee physiology are discussed; some insights about effects of negative temperatures are also presented. Finally, the last section deals with shading in harsh environments as a mean of buffering climatic fluctuations, as well as of increasing environmental sustainability in cof fee exploitation.

Comparison of resistance to drought of three bean cultivars

The aim of the present work was to evaluate oxidative stress and plant antioxidant system of three contrasting bean (Phaseolus vulgaris L.) genotypes in the response to drought. Drought was imposed 14 d after emergence, by withholding water, until leaf relative water content reached 65 %. Water stress increased lipid peroxidation (LPO), membrane injury index, H2O2 and OH⋅ production in leaves of stressed plants. Activities of the antioxidative enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APOX) increased significantly under water stress in all the studied cultivars, while catalase (CAT) increased in cvs. Plovdiv 10 and Prelom, but decreased in cv. Dobrudjanski ran. Furthermore cv. Plovdiv 10 which had the highest APOX and CAT activities also showed the lowest increase in H2O2 and OH⋅ production and LPO while cv. Dobrudjanski ran showed the lowest increases (and often the lowest values) in the antioxidant enzyme activities and the highest increases of H2O2 and OH⋅ production, and LPO. On the basis of the data obtained we could specify cv. Plovdiv 10 and cv. Prelom as drought tolerant and cv. Dobrudjanski ran as a drought sensitive.

Nitrogen dependent changes in antioxidant system and in fatty acid composition of chloroplast membranes from Coffea arabica L. plants submitted to high irradiance

Abstract In the present work we investigated the contribution of N availability to the changes in some antioxidant systems and in fatty acid composition of chloroplast membranes, in order to evaluate their role in the high light acclimation in coffee plants. Young coffee ( Coffea arabica L. cv. Catuai) plants, grown under low irradiance (up to 150 μmol m −2 s −1 ) with high (2 N ), medium (1 N ) and low (0 N ) N availability, were exposed to high irradiance (up to 1500 μmol m −2 s −1 ) for a maximal period of 15 days. Changes in several parameters were monitored during that period in the two top pairs of mature leaves. The formation rate of superoxide (O 2 ⋅− ) estimated by ESR ( K f ) did not differ among N -treatments before the onset of high light, but increased 70 and 30% in 0 N and 1 N plants, respectively, and decreased 33% in 2 N plants by the end of the stress. By this time, the chloroplastic activities of Cu,Zn-superoxide dismutase (Cu,Zn-SOD), ascorbate peroxidase (APer) and glutathione reductase (GRed) increased, respectively, 18, 225 and 138% in 2 N plants. The 0 N plants presented a 120% increase in Cu,Zn-SOD activity (which agrees with the higher K f of O 2 ⋅− ) and a 68% decrease in APer activity, suggesting an increase in H 2 O 2 levels, while GRed activity decreased 20%. The total carotenoid content was higher in 2 N plants and increased (about 20%) only in these plants by the end of stress. After 12 days of high irradiance, the total fatty acid (TFA) content increased about 30% in 2 N and 1 N plants, but did not significantly change in 0 N plants. In 2 N and 1 N plants a preferential synthesis of palmitic acid (16:0) and a decrease in the linolenic acid (18:3) percentage caused a decrease in the unsaturation level, which may have made the chloroplast membranes less susceptible to peroxidation. The N dependent changes observed in 2 N (and to a lesser extent in 1 N ) plants could represent adaptive features under the new high irradiance conditions, which increased the protection of the chloroplast structures against photooxidative stress.

Photosynthetic acclimation to high light conditions in mature leaves of Coffea arabica L. : role of xanthophylls, quenching mechanisms and nitrogen nutrition

Young coffee plants (Coffea arabica L. cv. Catuai), originally from a shaded habitat, were separated in three groups to be grown under different levels of N fertilization: 0.3 mmol N supplements were given to the soil every 7 days (high N treatment, 2N), every 15 days (medium N treatment, 1N) and every 45 days (low N treatment, 0N). These plants were later exposed to a high sunlight irradiance (noon PPFD up to 1500 µmol m–2 s–1 ) for a period of 12 or 15 days. Among others, the values of electron trans-port capacity, maximum carboxylation activity, photosynthetic capacity (Amax) and several fluorescence parameters (Fv/Fm, Fv´/Fm´, qP, pe) first showed a reduction (until the 4th–7th day) in all N treatments, followed by an N-dependent recovery. The 2N plants were less affected in the first few days and, at the end of the stress period, showed a better recovery for most of the studied parameters and the highest increase in the saturating PPFD for net photosynthesis and A max . The present work shows that the ability to acclimate displayed by the mature leaves of 2N plants was accompanied by an increase in energy dis-sipation mechanisms. These include an increase in the ‘high energy’ quenching and, mostly, the presence of higher contents of some xanthophylls (zeaxanthin and lutein) and carotenes, which helped to decrease the energetic overcharge in the photosystems. Pigment changes in mature leaves suggest that N can promote specific mechanisms of acclimation others than those that might be expected from a preferential partition of the element N into photosynthetic components.

Copper Inhibition of Rice Photosynthesis

Abstract Rice ( Oryza sativa L.) plants were grown over a 30-day period in nutrient solution containing concentrations of copper varying from 0.002 to 6.25 mg/L. Shoot contents of copper, net photosynthesis, intercellular C0 2 , stomatal conductance and photosynthetic capacity were measured. Copper concentration increased in the shoot with increasing levels of the metal in the solution, decreasing net photosynthesis and photosynthetic capacity above the 0.01 mg/L Cu treatment. Comparison of the effects of increasing copper concentrations on stomatal conductance to water and to intercellular CO 2 concentrations in relation to net photosynthesis showed no significant differences. Chlorophyll a fluorescence measurements, partly supported by measurements of ATP synthetase activity and electron microscopy studies of thylakoids, suggested a primary site of copper inhibition on the antenna chlorophyll a molecules of PSII. Our data suggest that this copper inhibition can be attributed to thermal damage of photosynthetic membranes, which in turn limits the yield of ATP and NADPH required for the reductive pentosephosphate cycle.

Biochemical and molecular characterization of the antioxidative system of Coffea sp. under cold conditions in genotypes with contrasting tolerance

Low positive temperature (chilling) is frequently linked to the promotion of oxidative stress conditions, and is of particular importance in the coffee plant due to its severe impact on growth, development, photosynthesis and production. Nevertheless, some acclimation ability has been reported within the Coffea genus, and is possibly related to oxidative stress control. Using an integrated biochemical and molecular approach, the characterization of the antioxidative system of genotypes with different cold acclimation abilities was performed. Experiments were carried out using 1.5-year-old coffee seedlings of Coffea canephora cv. Apoatã, C. arabica cv. Catuaí, C. dewevrei and 2 hybrids, Icatu (C. arabicaxC. canephora) and Piatã (C. dewevreixC. arabica) subjected to a gradual cold treatment and a recovery period. Icatu showed the greatest ability to control oxidative stress, as reflected by the enhancement of several antioxidative components (Cu,Zn-SOD and APX activities; ascorbate, alpha-tocopherol and chlorogenic acids (CGAs) contents) and lower reactive oxygen species contents (H(2)O(2) and OH). Gene expression studies show that GRed, DHAR and class III and IV chitinases might also be involved in the cold acclimation ability of Icatu. Catuaí showed intermediate acclimation ability through the reinforcement of some antioxidative molecules, usually to a lesser extent than that observed in Icatu. On the other hand, C. dewevrei showed the poorest response in terms of antioxidant accumulation, and also showed the greatest increase in OH values. The difference in the triggering of antioxidative traits supports the hypothesis of its importance to cold (and photoinhibition) tolerance in Coffea sp. and could provide a useful probe to identify tolerant genotypes.

High Irradiance Impairments on Photosynthetic Electron Transport, Ribulose-1,5-bisphosphate Carboxylase/ oxygenase and N Assimilation as a Function of N Availability in Coffea arabica L. Plants

Summary Young coffee (Coffea arabica L.) plants grown under low irradiance (PPFD up to ca. 150μmol m−2s−1) and high (2N), medium (IN) and low (ON) nitrogen availability conditions were exposed to natural sunlight (noon PPFD up to ca. 1,700 (¼mol m−2s−1) for 14–15 days, during which parameters related to photosynthesis and nitrogen assimilation were monitored. In the plants with lower N availability, a donor and an acceptor side photoinhibition may have affected PS II functioning. During the high irradiance stress the plants with higher N availability maintained the highest contents of cytochromes (cyt) b559HPJ, b559LP, b563 and f, and in plastoquinone-9 (PQ-9). Those plants also presented significant increases in rubisco content and activity, and a preferential investment in rubisco rather than in light harvesting components by the end of the high irradiance stress. Despite the effects observed on PSII and rubisco, the PS I activity and cyt b6/f complex were much more affected in all N treatments. Leaf nitrate reductase activity decreased whereas nitrate and amino acid contents increased during the high irradiance in 0N and 1N plants. Our data shows that high irradiance affected both the photochemical and enzymatic reactions of photosynthesis (especially in ON and 1N plants), that PS I was a preferential photoinhibitory target and that the higher N availability promoted the recovery of important physiological parameters, such as electron transport rates, PQ-9 and rubisco activity and content.

Effects of aluminum toxicity on nutrient accumulation in maize shoots: Implications on photosynthesis

Abstract The physiological characterization of aluminum (Al) toxicity in C4 plants prompted this study, having maize (Zea mays cv. XL‐72.3) used as a test system. Two weeks after germination, maize plants were submitted to increasing Al concentrations (from 0 up to 81 mg L‐1) for 20 days in a growth medium with low ionic strength, after which several analyses were carried out. In root tissues, Al concentrations significantly increased between the 0 and the 81 mg L‐1 Al treatment. In the shoots nitrogen (N), phosphorus (P), and iron (Fe) significantly decreased with increasing Al concentrations, but at different rates. Magnesium (Mg) showed a tendency to decrease for Al treatments higher than 9 mg L‐1, the opposite occurring with manganese (Mn) contents. Chlorophyll a fluorescence parameters Fo and Fv/Fm showed non‐significant changes, while photosynthetic capacity, electron transport rate associated with photosystem I and cytochromes (cyt) f and b563 contents decreased above the 9 mg L‐1 Al treatment. Alu...

The small GTPase Rab11 co-localizes with α-synuclein in intracellular inclusions and modulates its aggregation, secretion and toxicity

Alpha-synuclein (aSyn) misfolding and aggregation are pathological features common to several neurodegenerative diseases, including Parkinsons disease (PD). Mounting evidence suggests that aSyn can be secreted and transferred from cell to cell, participating in the propagation and spreading of pathological events. Rab11, a small GTPase, is an important regulator in both endocytic and secretory pathways. Here, we show that Rab11 is involved in regulating aSyn secretion. Rab11 knockdown or overexpression of either Rab11a wild-type (Rab11a WT) or Rab11a GDP-bound mutant (Rab11a S25N) increased secretion of aSyn. Furthermore, we demonstrate that Rab11 interacts with aSyn and is present in intracellular inclusions together with aSyn. Moreover, Rab11 reduces aSyn aggregation and toxicity. Our results suggest that Rab11 is involved in modulating the processes of aSyn secretion and aggregation, both of which are important mechanisms in the progression of aSyn pathology in PD and other synucleinopathies.

Photosynthetic performance and content of some nutrients in cadmium- and copper-treated barley plants

ABSTRACT Barley (Hordeum vulgare L. cv. CE9704) plants grown in sand culture were exposed to increasing cadmium (Cd) (0, 14, 28, and 42 mg Cd kg−1 sand) or copper (Cu) (0, 5, 10, and 15 mg Cu kg−1 sand) concentrations for a duration of 10 days. The effect of excess Cd or Cu on plant growth, selected mineral elements content, leaf gas exchanges, and chlorophyll content were studied. The excess of Cd or Cu inhibited relative growth rate (RGR) of barley plants mainly through net assimilation rate (NAR) retardation, but leaf area ratio (LAR) was barely affected or unaffected. After 10 days of exposure, the shoot content of Cd and Cu was about 1/10 (Cu) to 1/20 (Cd) that of roots. Cadmium- and Cu-treated plants with equal RGR inhibition had some differences in photosynthesis response and in the content of some nutrients, which were not distinctive enough. Stomatal limitation to photosynthesis in Cd-treated plants was well expressed, but in Cu-treated plants factors limiting photosynthesis were more related with mesophyll constraints. Cadmium and Cu treatment reduced the chlorophyll content, relative to untreated plants more probably through degradation of photosynthetic components. In conclusion, among observed physiological disturbances in Cd and Cu-treated barley plants with relatively equal growth inhibition, the similarities prevailed over the differences.