Metabolic process of the C-sugars on the translocation pathways of cucumber plants

Studies on the metabolic process of photoassimilates and enhancement of sugar accumulation into fruit are important in fruit crop production. The metabolic process of the ¹⁴C-photoassimilates in cucumber plants was analyzed with respect to the vascular system. At 4 h after the start of ¹⁴CO₂ feeding, the ¹⁴C-photoassimilates synthesized in a selected leaf on the main shoot were translocated to the vascular bundles of the internode just below the ¹⁴CO₂-fed leaf. The radioactivity of ¹⁴C-stachyose was as high as that of ¹⁴C-sucrose in the vascular bundles of petiole and internode just below the ¹⁴CO₂-fed leaf as well as in the midrib, while the radioactivity of ¹⁴C-stachyose was lower than that of ¹⁴C-sucrose in the mesophyll. The ¹⁴C-photoassimilates appeared to have been translocated without any metabolic change in the translocation pathways between the petiole and internode just below the ¹⁴CO₂-fed leaf, because the ratio of ¹⁴C-stachyose radioactivity in the two parts was similar. At 8 h after the start of ¹⁴CO₂ feeding, the ¹⁴C-photoassimilates were translocated to the fruit. In the vascular bundles of the peduncle, the ratios of the radioactivity of ¹⁴C-stachyose and ¹⁴C-raffinose were lower, and the ratio of the radioactivity of ¹⁴C-sucrose was higher, than that at the petiole and internode just below the ¹⁴CO₂-fed leaf at 8 h after the start of ¹⁴CO₂ feeding. Therefore, it seemed that ¹⁴C-stachyose and ¹⁴C-raffinose were hydrolyzed to ¹⁴C-sucrose in the peduncle.     

郁金香更新鳞茎发育的碳同化物积累与内源激素变化研究

 应用扫描电镜和¹⁴C同位素标记技术, 并结合内源激素测定, 考察郁金香更新鳞茎膨大发育与碳同化物积累、分配的关系。结果表明: 在鳞片细胞内观察到明显的淀粉颗粒, 并随鳞茎的发育进程充满整个细胞腔。在盛花期前, ¹⁴C同化物主要分配到地上部; 进入叶枯期后¹⁴ C同化物以向地下部运输为主,分配比例达66.01% , 其中更新鳞茎中¹⁴C同化物的分配占60.85% , 这时¹⁴C库活性表现为: 鳞茎>叶片>花茎>根系。在郁金香更新鳞茎发育进程中, 叶片中GA、IAA含量呈下降趋势, ABA含量则不断增高并在盛花期出现峰值, 达65.86 ng·g^{- 1} FM。比较不同生育期的GA₃ /ABA比值, 在发叶期的叶片和盛花期的更新鳞茎中均出现高比值, 表明内源激素的平衡可能是郁金香更新鳞茎发生和发育的调节因子。     

Photosynthesis and assimilate partitioning during rhythmic growth of green tea (Camellia sinensis var sinensis)

Summary

Shoot morphogenesis in green tea was used to define key events in development which occur during rhythmic growth. These stages are: stage I, no shoot extension or leaf expansion with a maximum number of leaf primordia in the apical bud; stage II, maximum shoot extension and leaf expansion; stage III, cessation of shoot extension and leaf initiation; and stage IV, cessation of leaf expansion while leaf initiation in the apical bud recommences. The apical bud appears dormant during both stages III and IV. Leaf primordia initiated during stage IV expand to form the new shoot during stages I to III. The newly expanded leaves are harvested, forming the green tea crop. Photosynthetic capacity and the pattern of carbohydrate partitioning vary during shoot growth, as defined by the stages of development. Net photosynthesis of mature, fully expanded leaves was highest (18.0 ;C;mol C0₂ m^–2s^–1) during stage I, at the beginning shoot growth and lowest (13.2 μmol C0₂ m^–2s^–1) during stage III, at the cessation of shoot extension. Maximum starch reserves in leaves and internodes of 12.5% (dw) and 22% respectively were reached at the cessation of shoot extension, during stage III, and declined significantly to 0% and 9% respectively at the start of shoot growth during stage I. At the start of shoot growth, the major part of ¹⁴C label was partitioned to the bud, with the developing leaf primordia assumed to be the major sink organs as leaf initiation had ceased. Changes in sink activity with ontogeny are linked to changes in both photosynthesis and partitioning of assimilates during shoot growth and culminate in rhythmic growth of tea.     

Critical ethylene exposure for Capsicum annuum ‘Janne’ is dependent on an interaction between concentration,duration and developmental stage

Summary

Two ethylene experiments were designed to show the reaction of the pot plant Capsicum annuum ‘Janne’ to ethylene and to define the critical level of ethylene exposure. The ethylene exposure consisted of 72 h of darkness at 19°C, an ethylene duration of 6–72 h and ethylene concentrations of 0.05–5.0 µl l^?1. After the plants had been exposed to ethylene they were placed in a post-production evaluation room. The response of capsicum to ethylene, as expressed by leaf and fruit abscission, was dependent on developmental stage, duration of ethylene exposure and ethylene concentration. Leaves were the most ethylene-sensitive plant parts, followed by the green and maroon fruits. Ethylene did not affect the rate of development into red fruits. The most developed plants were less sensitive to ethylene. Capsicum is very sensitive to ethylene, e.g. there was significant abscission of leaves after exposure to an ethylene concentration of 1.0 µl l^?1 for 12 h and a significant abscission of leaves and green fruit after exposure to 0.05 µl^?1 for 72 h. A critical ethylene exposure is suggested, dependent on plant sensitivity, duration of ethylene exposure and ethylene concentration.     

Growth,allocation of N and carbohydrates,and stomatal conductance of greenhouse grown apple treated with prohexadione-Ca and gibberellins

Summary

Potted M.26 apple (Mahis domestica) liners were treated with the gibberellin biosynthesis inhibitor prohexadione-Ca (Apogee®) at 0 to 500 mg l”¹ as a foliar spray. Apogee inhibited stem elongation, leaf formation, total leaf area and shoot dry weight, while significantly increasing specific leaf weight, root dry weight and root: shoot ratio, regardless of rate. Foliar application of gibberellin A4₊₇ (GA4₊₇) at 200 mg l”¹ to Apogee-treated plants one day later reversed these effects, especially stem elongation, root dry-matter production and root: shoot ratio. Apogee increased N concentration in stems but not in leaves and roots. There was no effect on the pattern of N allocation amongst organs. GA4+7 increased leaf N concentration but decreased stem and root N concentrations compared with untreated controls, with N allocation shifting from roots to stem. Total nonstructural carbohydrates (TNC), expressed either on a concentration or content basis, increased in all parts of the Apogee-treated plants, due to increased levels of starch rather than soluble sugars, without altering allocation pattern. Conversely, GA4₊₇ reduced TNC levels (mainly starch levels) in all parts, with the pattern of allocation slightly shifted from roots to stem. The afternoon decline in stomatal conductance occurred earlier in the Apogee treated plants, measured 10 d after stem elongation had ceased. Starch buildup in the Apogee-treated plants appeared to be associated with this effect, suggesting an involvement of a feedback inhibition of photosynthesis in the Apogee-induced stomatal control.     

蚯蚓粪复合基质氮素添加量对番茄幼苗生长的影响

研究了蚯蚓粪复合基质中尿素添加量处理对番茄幼苗生长的影响。结果表明:蚯蚓粪复合基质处理的各项指标明显优于对照基质。蚯蚓粪复合基质中尿素添加量为0.5kg·m-3时苗前期幼苗株高、茎粗、叶片数和苗中期幼苗株高、开展度、茎粗最大;尿素添加量为1.0kg·m-3时苗前期及中期幼苗的叶绿素和成苗期的茎粗、叶片数最大;尿素添加量为2.0kg·m-3时苗前期及中期幼苗叶片数和苗前期、成苗期的开展度以及成苗期的株高最大。苗中期尿素添加量为0.5kg·m-3时根长最长,尿素添加量为2.0kg·m-3时根表面积、根直径、根体积最大。可见在番茄育苗中蚯蚓粪复合基质完全可以替代传统基质,苗前期及中期尿素添加量以0.5kg·m-3效果好,添加高量尿素(2.0kg·m-3)在成苗期的促苗效果逐步显现,尿素添加量以0.5kg·m-3最有利于形成壮苗。     

Low Water Tensions in Defined Growth Stages of Processing Tomato Plants and their Effects on Yield and Quality

In drip irrigation experiments where water was applied daily it was found that low water tensions could be maintained in the soil to a range of 10 to 20 centibars and that these conditions had a considerable influence on yield and quality of processing tomatoes, Lycopersicon esculentum cv VF 317. The response of the plant in different growth stages to low soil water tensions was studied. Irrigation during the period of fruit set and fruit development was found to increase yield levels by 53 t ha^-1 compared with non-irrigated plants. Irrigation applied only during the period of fruit development had a favourable influence on yield as well as on the efficiency of water utilization. However, irrigation at this stage had an unfavourable influence on fruit quality characteristics, namely, total soluble solids, acidity, viscosity and vitamin C. The effects of irrigation on fruit set and fruit development are discussed.     

Effects of salinity at two ripening stages on the fruit quality of single-truss tomato grown in hydroponics

Summary

Single-truss tomato plants grown hydroponically (wet-sheet culture) were exposed to a salinity (EC) of 5.0 dS m²¹ or 8.0 dS m²¹ at two fruit ripening stages, the immature green stage and the decolouring stage. These salinities were achieved by adding NaCl to the standard solution, which had an EC of 2.4 dS m²¹. Increased salinity at the immature green stage improved fruit quality more than increased salinity at the decolouring stage but decreased fruit yield more. The reduction in fruit yield was due to a decrease in fruit weight but not in fruit number. Salinity increased the concentration of soluble solids, citrate, ascorbic acid, K, chlorophyll a, chlorophyll b, lycopene, and carotene in the fruit, but the absolute amount of these constituents per fruit was decreased or not affected. These results suggest that the improvement in fruit quality induced by the salinity is caused by the reduction of water import into the fruit. The effectiveness of both salinities was significantly bigger when it was applied at the earlier development stage, suggesting that mature fruit would be less sensitive to strength of the EC.     

荔枝果皮对外源钙和蔗糖吸收及向细胞壁沉着的研究

利用放射性同位素示踪技术研究荔枝果皮对外源钙和蔗糖的吸收及细胞壁构建规律。结果表明,进入果皮的蔗糖主要被用以构建细胞壁,但随果实发育,蔗糖用于构建细胞壁比例减少,更多分布于果皮组织的可溶性成分中;果梗向果实运输钙的效率远远低于蔗糖运输效率;NAA处理果实短期内可明显促进蔗糖向果实运输,但不能促进果梗的钙进入果实,说明蔗糖和钙向果实运输有不同调控机制;施于果实表面的钙虽可被吸收并成为细胞壁的结构钙,但比例不到千分之一;硝酸(根)离子和NAA可一定程度促进外源钙向细胞壁沉着;抗裂的怀枝果皮细胞壁的钙含量比易裂的糯米糍高,其细胞壁结合外源钙的能力也强于后者,说明前者细胞壁中果胶半乳糖醛酸残基含量高于后者,也是怀枝具有较强抗裂性的物质基础之一;2品种14C-蔗糖向果皮细胞壁沉着均在果实发育初期最活跃,怀枝细胞壁构建也只是在果实发育初期比糯米糍更活跃,这就意味着抗裂性形成的关键时期是在果皮发育的初期。     

Effects of Trichoderma harzianum strain T-22 on the growth of two Prunus rootstocks during the rooting phase

Summary

Trichoderma harzianum strain T-22 (T22) is one of the most effective strains of this fungus that is able to colonise the roots of most plant species across a wide range of soil types. This fungus is used as a biocontrol agent during crop production, and for the improvement of the rooting and acclimatisation phases in plant nurseries. In vitro-cultured shoots of GiSeLa6^® (Prunus cerasus P. canescens) and of GF677 (P. amygdalus P. persica), two important Prunus varieties used as commercial rootstocks, were inoculated with T22. The results showed that early inoculation of the fungus (at the stage of shoot transfer to root-inducing medium) seriously damaged both GiSeLa6^® and GF677 plants; whereas, following later inoculation (7 d after shoot transfer to root-inducing medium), the plants survived and showed significant increases in shoot growth and root development. In particular, root lengths in GiSeLa6^® and GF677 plants increased by 180% and 136%, respectively, compared to non-inoculated controls. Microscopic analysis revealed T22 hyphae spreading on the root surface in GiSeLa6^® (fungus colonisation frequency = 20%), but not in GF677 roots. Our results demonstrate that the application of T22 during the rooting phase resulted in greater shoot lengths, as well as increased numbers of leaves, roots, and stem diameters. These morphological characteristics could increase the quality and viability of nursery planting material and provide advantages during the plant acclimatisation phase.     

Plant density studies with direct seeded tomatoes in Ontario, Canada

In direct seeded tomato density experiments with constant rectangularity of 1.0 carried out at Preston and Simcoe Research Stations, Ontario, Canada in 1971, the effect of increasing plant density from 4.2 to 62.1 plants/m² was to increase total plant weight, total fruit weight and ripe fruit weight per unit area. The proportion of ripe fruit to total fruit increased with increased density, and ripe fruit yields from a single harvest of up to 14 kg/m² were obtained.Using the reciprocal yield-density equation (when W is the mean weight per plant (or plant part) at density , A and B are constants, and density is the only variable) to analyse the experiments, showed that both the A and B constants were influenced by cultivar while the A constant was influenced more by fertilizer application than was the B constant. In general the effect of increased fertilizer was to increase the yield potential ( ) for total plant weight and total fruit weight, but this effect was not so marked for ripe fruit weight.     

Mechanisms of salt stress tolerance in two rose rootstocks: Rosa chinensis ‘Major’ and R. rubiginosa

The responses of two rose rootstocks Rosa chinensis ‘Major’ and R. rubiginosa were investigated under salt stress. The distribution of chloride and sodium ions in all plant parts was determined. The salt treatments were applied through irrigation water containing 0, 5, 10, 20 and 30 mM NaCl. Necrosis on the leaves as a result of the NaCl treatments was observed with in rootstocks after two months. Leaf injury was more pronounced in R. chinensis ‘Major’ than R. rubiginosa. The rootstock R. rubiginosa showed a higher tolerance to the NaCl stress than R. chinensis ‘Major’. The survival of the plants under increased NaCl stress as well as the extent of leaf injury could be used in the determination of tolerance of the rose genotypes. The lower older leaves contained higher concentrations of Cl⁻ than the young upper leaves. Leaf samples had higher concentrations of Cl⁻ than stem samples taken from the same positions. The roots contained higher amounts of Cl⁻ than the stem samples. The plants accumulated higher amounts of Cl⁻ in comparison with Na⁺. The lower leaves of R. chinensis ‘Major’ had higher amounts of Na⁺ than in all other parts whereas R. rubiginosa had higher concentrations of Na⁺ in the roots than in all other parts.     

喷施硅酸钠对结果后期草莓生长、品质和产量的影响

为了提升草莓生产后期果实品质，通过叶面喷施不同浓度（0.5、1.0、1.5 mmol/L）硅酸钠，研究草莓生长后期植株长势以及果实硬度、品质和产量的变化情况。结果表明：喷施1.0 mmol/L硅酸钠处理效果最好，生长指标、品质指标和产量指标均表现较好，且抑制了植株徒长，与CK相比较，草莓株高显著降低11.1%，茎粗显著增加15%；喷施后10 d新叶叶绿素生长量增大80%，果实硬度变化幅度增加6%;8成熟、9成熟、10成熟果实硬度分别显著提高65.9%、81.5%、86.8%，果实糖度分别增加8.70%、3.17%、10.77%；平均单果质量、行产量、测产行产量分别增加2.8%、12.9%、8.0%，畸形果率则降低3.6百分点。建议在草莓结果后期酌情使用。     

Effect of light conditions on the development of the inflorescence in tomato

By growing tomato plants (Lycopersicon esculentum Mill.) in 4 different light regimes (2 photoperiods — 8 and 16 h — combined with 2 light intensities — 9,000 and 18,000 ergs cm^?2 s^?1, it was shown that increasing light integrals hastened flower initiation, greatly promoted the development of the inflorescence and increased the rates of leaf production and the growth of the stem. In similar light integrals, flower initiation was earlier and inflorescence development far better in short photoperiods than in long ones; the rates of leaf production were almost the same and stem growth was greater in long days.Transfer experiments from favourable to insufficient light conditions and inverse transfers at different times during the life of the plant indicated that light conditions were critical at the time of, and after, the macroscopic appearance of the inflorescence. At that stage, a transfer to low light conditions for 10 days induced complete abortion of the truss in our growth conditions. The effect of a transfer from insufficient to favourable light conditions was slower since at least 15 days in these latter conditions were required in order to achieve the development of the inflorescence.     

Methyl jasmonate plays a role in fruit ripening of ‘Pajaro’ strawberry through stimulation of ethylene biosynthesis

The role of methyl jasmonate (MJ) in strawberry (Fragaria × ananassa Duch. cv Pajaro) fruit ripening was investigated by monitoring its endogenous concentrations in fruit at various stages of development and the effects of exogenously applied MJ at these stages on ethylene biosynthesis. The concentration of endogenous trans-MJ was significantly higher in the white fruit (31.7–162.2 ng g⁻¹) and decreased sharply in half and fully ripe fruit. Higher concentrations of endogenous trans-MJ at the white stage of strawberry fruit development followed by a decline during fruit ripening indicate that MJ may play an important role in modulating fruit ripening. Significantly increased ethylene production was measured in the fruit when MJ was applied at white, half ripe and at fully ripe stage. The application of MJ (50 μM) resulted in significantly highest ethylene production and increased activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase as compared to all other treatments. The effect of exogenously applied MJ on ethylene production, ACC synthase and ACC oxidase activities was dependent on concentration of MJ applied and on fruit developmental stage. In conclusion, MJ in strawberry modulates fruit ripening, as its concentration is higher in white fruit and is declined with the progression of ripening and exogenous application of MJ increases ethylene production, activities of ACC oxidase and ACC synthase depending upon the concentration of MJ applied and fruit developmental stage.     

The addition of gibberellic acid to auxin solutions increases sugar accumulation and sink strength in developing auxin-induced parthenocarpic tomato fruits

The effects of the addition of gibberellic acid (GA) to auxin solutions for tomato fruit setting on sugar content and titratable acidity at maturity were investigated in ‘Louis 60’ tomatoes, and sucrolytic enzyme activities and cell development during the early stages of fruit development were examined to explain the physiological mechanisms. Days to maturity and titratable acidity were not affected by GA addition. The sugar concentration of the pericarp was increased by 50 mg L⁻¹ of GA addition in the summer and the spring, but not in the autumn experiment. The product of sugar concentration and fruit weight, which is thought to reflect the amount of sugar per fruit, was higher in GA-treated fruit in every experiment. Beginning 1 day after treatment, cell size was larger in GA-treated fruit and resulted in an increase in pericarp thickness at maturity. These results suggest that GA addition at anthesis can promote an increased sink size of individual pericarp cells immediately after treatment. The activities of VAI and neutral invertase (NI) were higher in GA-treated fruit around 5 days after treatment, and the possibility of VAI and/or NI involvement in sink activity at an early stage of fruit development is suggested.     

温州蜜柑同化产物运转分配的调控

采用~(14)C示踪技术探讨人工脱叶、植物激素对枳砧宫川温州蜜柑同化产物运转分配的调控,植物生长调节剂对植物整体同化产物分配的影响,以及源—库关系中植物激素的作用。结果表明,人工脱叶后~(14)C—同化产物大量向脱叶区域运转,摘除植株下部叶片,同化产物不仅向植株下部运输,而且向根部运转,脱叶还可提高源叶输出率。向果实内注入GA_2,促进源叶同化产物向同枝与源叶呈直线的果实内不同区域运转,但源叶与果实的距离延长时,GA_2这种促进作用消失。ABA有抑制GA_2促进同化产物运转的作用。PP333和调节膦对叶片向根系输送~(14)C—同化产物的量相似,但两者对地上部同化产物分配的作用相反,PP333促进同化产物向其他施用部位运转,调节膦抑制这一过程,两者混用,PP333的作用被调节膦掩盖,表现抑制同化产物运转,但同时有可能促进同化产物向根系运转。     

Determination of the uptake and translocation of nitrogen applied at different growth stages of a melon crop (Cucumis melo L.) using N isotope

In order to establish a rational nitrogen (N) fertilisation and reduce groundwater contamination, a clearer understanding of the N distribution through the growing season and its dynamics inside the plant is crucial. In two successive years, a melon crop (Cucumis melo L. cv. Sancho) was grown under field conditions to determine the uptake of N fertiliser, applied by means of fertigation at different stages of plant growth, and to follow the translocation of N in the plant using ¹⁵N-labelled N. In 2006, two experiments were carried out. In the first experiment, labelled ¹⁵N fertiliser was supplied at the female-bloom stage and in the second, at the end of fruit ripening. Labelled ¹⁵N fertiliser was made from ¹⁵NH₄¹⁵NO₃ (10 at.% ¹⁵N) and 9.6 kg N ha⁻¹ were applied in each experiment over 6 days (1.6 kg N ha⁻¹ d⁻¹). In 2007, the ¹⁵N treatment consisted of applying 20.4 kg N ha⁻¹ as ¹⁵NH₄¹⁵NO₃ (10 at.% ¹⁵N) in the middle of fruit growth, over 6 days (3.4 kg N ha⁻¹ d⁻¹). In addition, 93 and 95 kg N ha⁻¹ were supplied daily by fertigation as ammonium nitrate in 2006 and 2007, respectively. The results obtained in 2006 suggest that the uptake of N derived from labelled fertiliser by the above-ground parts of the plants was not affected by the time of fertiliser application. At the female-flowering and fruit-ripening stages, the N content derived from ¹⁵N-labelled fertiliser was close to 0.435 g m⁻² (about 45% of the N applied), while in the middle of fruit growth it was 1.45 g m⁻² (71% of the N applied). The N application time affected the amount of N derived from labelled fertiliser that was translocated to the fruits. When the N was supplied later, the N translocation was lower, ranging between 54% at female flowering and 32% at the end of fruit ripening. Approximately 85% of the N translocated came from the leaf when the N was applied at female flowering or in the middle of fruit growth. This value decreased to 72% when the ¹⁵N application was at the end of fruit ripening. The ammonium nitrate became available to the plant between 2 and 2.5 weeks after its application. Although the leaf N uptake varied during the crop cycle, the N absorption rate in the whole plant was linear, suggesting that the melon crop could be fertilised with constant daily N amounts until 2–3 weeks before the last harvest.     

Essential and non-essential element composition of tomato plants fertilized with poultry manure

Poultry manure (PM) must be disposed of from poultry farms, but is a potentially valuable source of macro- and micronutrients for plant growth. The objective of this study was to examine the effects of poultry manure on the growth of tomato (Lycopersicon esculentum) plants. Yields of fruits and vegetative material of plants grown in soil with 0, 10, 20 and 40 g kg⁻¹ PM added were measured. Concentrations of N, P, K, Ca, Mg, S, Fe, Zn, Cu, Mn, Mo, Cl, Si, Br, Rb, Sr and Ba in leaves at flowering and at final harvest and in fruits were determined by polarized energy dispersive X-ray fluorescence (PEDXRF). Poultry manure fertilization improved tomato shoot growth and also fruit yield and increased leaf N concentrations at the harvest stage. In addition, P concentrations of the leaves and fruits were increased as the application rate of PM was increased. Fruit Ca and Mg were significantly reduced by increased rate of PM application, but not to the extent to cause the calcium deficiency disorder blossom end rot. Applied high levels of PM slightly increased the concentrations of leaf Mo and Br at the harvest stage. Poultry manure applications had a positive effect on the concentrations of leaf Zn, Cu, Cl and Rb at both sampling stages, but leaf Si concentration was reduced by PM treatments. The concentrations of Zn and Rb were increased in the fruits by PM treatments, but the concentrations of Br were decreased. Applied PM levels had no significant effects on the concentrations of K, S, Fe, Sr or Ba in tomato plants. It is concluded that the increased fruit yield, and the increased concentration of Zn (an element required in the human diet) and the lowered concentration of potentially harmful Br in the fruit make poultry manure a valuable growing medium for tomato production.     

Nitrogen and irradiance levels affecting net photosynthesis and growth of young coffee plants (Coffea arabica L.)

Summary

Shoot growth attributes, leaf anatomical changes and net photosynthetic rates were determined in young coffee plants fertilized at high and low levels and subjected to shade or full sunlight. High nitrogen supply increased plant height irrespective of the light level imposed during growth, and promoted a larger leaf area in plants of the shade treatment. Specific leaf weight was 15% higher in plants grown in full sunlight than in shaded plants, at both nitrogen levels. The number of leaves developed on the orthotropic stem increased significantly under full irradiance and high nitrogen availability. Leaves were 11% thicker ih unshaded plants than in shaded ones, because of the increased size of the palisade and spongy parenchyma tissues. More thylakoids per granum and more grana per chloroplast were observed in shade-grown plants, mainly in those given high nitrogen treatment. Total nitrogen content expressed on a leaf-area basis was higher in sun plants supplemented with nitrogen, whereas chlorophyll a and b and protochlorophyll contents increased in shade-grown plants. Net photosynthetic rate in high nitrogen plants reached 7.19 µmol CO₂ m^?2 s^?1 in the full irradiance treatment, and 5.46 µmol CO₂ m^?2 s^?1 in shaded plants. Maximum net photosynthetic rates in the low nitrogen plants were 5.28 and 4.90 µmol CO₂ m^?2 s^?1 in sun and shade plants, respectively. Increased photosynthetic light saturation was observed in high irradiance plants (628 µmol m^?2 s^?1) relative to shade plants (359 µmol m^?2 s^?1) in the high nitrogen treatment. The same pattern was observed in low nitrogen plants. The apparent quantum yield of shade acclimated plants was 14% higher than in those grown in full sunlight. Our results indicate that coffee may be classified as a facultative shade species, exhibiting features of sun adapted plants coupled with shade acclimation attributes, this fairly high adaptive capacity to shade:sun transition being strongly influenced by the level of nitrogen nutrition given to the plants.