Moacyr Maestri

Ecophysiology of coffee growth and production

, which together account for 99% of the world coffee bean production. Thisreview is organized into sections dealing with (i) climatic factors and environmental requirements, (ii) root and shootgrowth, (iii) blossoming synchronisation, fruiting and cup quality, (iv) competition between vegetative andreproductive growth and branch die-back, (v) photosynthesis and crop yield, (vi) physiological components of cropyield, (vii) shading and agroforestry systems, and (viii) high-density plantings.

Differential responses of superoxide dismutase in freezing resistant Solanum curtilobum and freezing sensitive Solanum tuberosum subjected to oxidative and water stress

In photosynthetic tissues superoxide dismutase (SOD) plays an important role by scavenging the superoxide radical whose production is an usual reaction in chloroplast thylakoids. To test the differential response of SOD, two Andean potato species differing in frost resistance, Solanum curtilobum (frost resistant) and Solanum tuberosum (frost sensitive), were subjected to methyl viologen-mediated oxidative stress and polyethylene glycol (PEG)-induced water stress. A significant increment (approximately two-fold) in total SOD and FeSOD activity, which occupied about 50% of the total activity, was found when leaves of S. curtilobum were exposed to water stress. In contrast, the SOD activity in leaves of S. tuberosum remained unchanged. The exposure of leaves of S. curtilobum to oxidative stress increased total SOD and FeSOD activity by 350%. High correlation between SOD activity and the F(v)/F(m )ratio under both PEG induced water stress and MV-mediated oxidative stress was observed. This suggests that SOD can protect PSII from superoxide generated by oxidative and water stress. The higher SOD activity could be an important mechanism to explain why some natives Andean potato like S. curtilobum are more resistant to abiotic stresses than S. tuberosum.

In vitro salt tolerance and proline accumulation in Andean potato (Solanum spp.) differing in frost resistance

Abstract Four species of potato ( Solanum andigena, Solanum curtilobum, Solanum juzepczukii and Solanum tuberosum L.) differing in frost resistance were subjected to various levels of salinity conditions (NaCl). Salt resistance was measured by survival, growth and proline content of the stressed plantlets. Each Solanum species studied responded differently to salt stress. Growth of S. andigena and S. tuberosum was inhibited by given range levels of NaCl. However, the frost resistant genotypes S. juzepczuckii and S. curtilobum showed high salt tolerance (up to 200 mol/m 3 NaCl). The salt tolerance was positively related to leaf proline content. There was a close relationship ( r 2 = 0.95) between the growth and survival of plantlets with proline content. Results suggest that proline accumulation could be used as a biochemical marker for increased salt tolerance in potato.

DECLINE OF VEGETATIVE GROWTH IN COFFEA ARABICA L. IN RELATION TO LEAF TEMPERATURE, WATER POTENTIAL AND STOMATAL CONDUCTANCE

Abstract The decline of vegetative growth of Arabica coffee trees in Vicosa (20° 45′ S, 650 m altitude), Brazil, occurring from mid-March through late May, was observed in both irrigated and non-irrigated plants and did not show a direct relation with leaf water potential. Declining growth coincided with lowering temperatures, and particularly with increasing daily periods with low temperatures. Stomatal conductances in the morning (0800–0900 h) were relatively high until mid-March and decreased gradually in parallel with declining growth rates. During the quiescent growth phase in the cool season, starting from late May, stomata were closed for most of the diurnal period.

Photosynthesis in coffee (Coffea arabica and C. canephora) as affected by winter and summer conditions

Abstract Photosynthetic and biochemical responses of potted plants of Coffea arabica cv Red Catuai and C. canephora cv Kouillou were examined during winter and summer. There were large decreases in the photosynthetic rates of both cultivars from summer to winter, with more pronounced declines shown by Catuai. The photochemical efficiency of photosystem II, as evaluated by the ratio of variable to maximum chlorophyll fluorescence, decreased to a greater extent in Catuai than in Kouillou during winter. This probably was a secondary effect due to the loss of the photosynthetic capacity, which was mostly determined by non-stomatal factors. In response to winter conditions, Kouillou accumulated three times more proline and ascorbate with no changes in the content of malonedialdehyde (MDA). Catuai accumulated 160% more proline and 206% more MDA in winter in comparison to summer values, but there was no significant change in ascorbate levels. The content of chlorophylls and carotenoids did not change in response to natural seasonal acclimation. The leaf starch content in winter was higher by 53% in Catuai than in Kouillou. Photosynthetic rates, as measured by oxygen evolution, were well correlated with starch content in Catuai, but not in Kouillou. When winter-grown leaves were darkened for 96 h, their normal starch levels were halved; this was accompanied by the restoration of the photosynthetic rates to levels similar to those found in summer in both cultivars, with a concurrent resumption of the photosystem II efficiency.

Photosynthetic performance of two coffee species under drought

Coffea arabica cv. Red Catuaí and C. canephora cv. Kouillou were grown in pots beneath a plastic shelter. When they were 14 months old, irrigation was withheld until the leaf pre-dawn water potential was about -1.5 and -2.7 MPa (designated mild and severe water stress, respectively). Under mild stress, net photosynthetic rate (PN) decreased mainly as a consequence of stomatal limitations in Kouillou, whereas such decreases were dominated by non-stomatal limitations in Catuaí. Under severe drought, further decreases in PN and apparent quantum yield were not associated to any changes in stomatal conductance in either cultivar. Decreases were much more pronounced in Catuaí than in Kouillou, the latter maintained carbon gain at the expense of water conservation. In both cultivars the initial chlorophyll (Chl) fluorescence slightly increased with no changes in the quantum efficiency of photosystem 2. In response to rapidly imposed drought, the Chl content did not change while saccharide content increased and starch content decreased. Photoinhibition and recovery of photosynthesis, as evaluated by the ratio of variable to maximum fluorescence and by the photosynthetic O2 evolution, were unaffected by mild drought stress. Photoinhibition was enhanced under severe water deficit, especially in Catuaí. In this cultivar the O2 evolution did not resume upon reversal from photoinhibition, in contrast to the complete recovery in Kouillou.

Accumulation of proline and quaternary ammonium compounds in mature leaves of water stressed coffee plants (Coffea arabica and C. canephora)

SummaryWater stressed coffee plants of five genotypes of C. arabica and one of C. canephora were compared with watered controls for their accumulation of proline and quaternary ammonium compounds. These solutes, mainly proline, accumulated in mature leaves under water stress, their concentration being related to the osmotic potential at zero turgor and to the osmotic adjustment either in well watered or droughted plants. Proline accumulated to a greater extent than quaternary ammonium compounds under water stress.

WATER RELATIONS OF COFFEE LEAVES (COFFEA ARABICA AND C. CANEPHORA) IN RESPONSE TO DROUGHT

Coffee plants of five Arabica and one Canephora genotypes were raised in containers with 0.02 nr1 of soil, under a clear plastic shelter. When they were 18 months old, irrigation was withheld until...

Photoinhibition and recovery of photosynthesis in Coffea arabica and C. canephora

Photosynthetic parameters were determined in disks from leaves of C. arabica cv. Red Catuaí and C. canephora cv. Kouillou grown in the field. Kouillou showed a relatively higher irradiance requirement for saturating photosynthesis, lower chlorophyll (Chl) content, and higher Chl a/b ratio than Catuaí. Photoinhibition of photosynthesis under bright irradiance was manifested by decreases in maximum photochemical efficiency (evaluated by the variable to maximum fluorescence ratio, Fv/Fm), as a consequence of an increased initial and a quenched maximum fluorescence. Restoration of Fv/Fm following photoinhibition in low irradiance was faster in Kouillou than in Catuaí. Chloramphenicol both accelerated photoinhibition (mainly in Kouillou) and blocked its recovery for at least 190 min in either cultivar. Photosynthetic oxygen evolution under photoinhibitory conditions was decreased by chloramphenicol; in control leaf disks this decrease was only observed in C. arabica, but with a rapid recovery within 90 min of low irradiance exposure. In both coffee cultivars, the depressed photochemical efficiency of photosystem 2 was not accompanied by a concomitant lowering in oxygen evolution during reversal from photoinhibition.