From Guadeloupe (French West Indies)

Original article

Influence of shade on photosynthetic gas exchange of 7 tropical rain-forest species from Guadeloupe (French West Indies)

M Ducrey

INRA, Laboratoire de Recherches Forestières Méditerranéennes, avenue A-Vivaldi, F-84000 Avignon, France

(Received 16 November 1992; accepted 21 September 1993)

Summary — Young seedlings from 7 tropical rain-forest species of Guadeloupe (French West In- dies): Dacryodes excelsa, Amanoa caribaea, Richeria grandis, Simaruba amara, Symphonia globulifera, Byrsonima coriacea and Podocarpus coriaceus were grown for 1-2 yr in full sunlight or under 4 artificially shaded tunnels transmitting 6, 11, 19 and 54% daylight. Photosynthetic gas exchanges of attached leaves or branches were then studied in the laboratory. Net photosynthesis-light curves were analysed for an average of 4 seedlings per species and per light treatment. Maximum photosynthesis on a leaf-area basis of sungrown seedlings varied from 3.4 μmol CO2 m-2 s-1 for Da- cryodes excelsa to 7.9 μmol CO2 m-2 s-1 for Simaruba amara. For all the species studied and when the measurements were expressed on a leaf-area basis, maximum photosynthesis of sun-grown seedlings was higher than for shade-grown seedlings. The opposite was observed for photosynthesis under limited light and for apparent quantum yield. We also observed a decrease in maximum photosynthesis and an increase in apparent quantum yield when specific leaf area increased, ie when the plants were more shaded. The range of variation in photosynthetic response between full sunlight and full shade made it possible to characterize the photosynthetic plasticity of the species. The results were compared with those obtained for other tropical rain-forest species. They are dis- cussed in terms of photosynthetic and morphological plasticity, shade adaptation, and of the species’ place in tropical rain-forest succession. tropical rain forest I forest succession I shade tolerance I net photosynthesis I photosynthetic plasticity

Résumé — Influence de l’ombrage sur les échanges gazeux photosynthétiques de 7 espèces de la forêt tropicale humide de Guadeloupe (Petites Antilles). De jeunes semis de 7 espèces de la forêt tropicale humide de Guadeloupe (Petites Antilles) : Dacryodes excelsa, Amanoa caribaea, Richeria grandis, Simaruba amara, Symphonia globulifera, Byrsonima coriacea et Podocarpus coriaceus ont été élevés pendant 1 à 2 ans en pleine lumière et sous 4 tunnels artificiellement ombragés laissant passer 6%, 11%, 19% et 54% de la pleine lumière. À la fin de cette période, on a étudié au laboratoire les échanges gazeux photosynthétiques de feuilles ou de rameaux rattachés aux jeunes plants. Des courbes photosynthèse nette - éclairement ont ainsi été réalisées en moyenne pour 4 plants par espèce et par tunnel. La photosynthèse maximale des plants de pleine lumière varie de 3,4 μmol CO2 m-2 s-1 pour Dacryodes excelsa à 7,9 μmol CO2 m-2 s-1 pour Simaruba amara. Pour toutes les espèces étudiées et lorsque les mesures sont rapportées à l’unité de surface foliaire, la photosynthèse maximale des plants de pleine lumière est supérieure à celle des plants d’ombre, tan- dis que l’on observe l’inverse pour la photosynthèse en éclairement limitant et pour le rendement quantique apparent. On note parallèlement une diminution de la photosynthèse maximale et une aug- mentation du rendement quantique apparent lorsque la surface spécifique des feuilles augmente, c’est-à-dire quand les plants sont de plus en plus ombragés. L’amplitude des variations de photosyn- thèse entre la pleine lumière et le plus fort ombrage permet de caractériser la plasticité photosynthéti- que des espèces. Les résultats sont comparés à ceux obtenus avec d’autres espèces forestières de la zone tropicale humide. Ils sont enfin discutés en termes de plasticité morphologique et photosyn- thétique, d’adaptation à l’ombrage, et d’emplacement dans le cycle de succession des espèces dans les forêts tropicales humides. forêt tropicale humide / succession forestière / tolérance à l’ombrage / photosynthèse nette / plasticité photosynthétique

INTRODUCTION foresters in the silvicultural management of forest stands. Baker’s (1949) tables of tol- The morphological, anatomical, structural, erance for conifers and hardwood species ultrastructural, biochemical or photosyn- of North America are an example. thetic response of herbaceous species Generally, shade-intolerant forest spe- and shrubs to different light conditions dur- cies are characterized by higher photosyn- ing growth is well known (eg, Boardman, thetic potentials than those of shade- 1977; Björkman, 1981; and Givnish, tolerant species. However, what differen- 1988). In general, the light-saturated rate tiates the species and makes it possible to of photosynthesis, the light compensation classify them in relation to one another, is point, and the light saturation plateau are the possible capacity for intolerant species higher for sun-grown plants than for to tolerate more or less shade, and for tol- shade-grown plants. On the other hand, erant species to survive in high light condi- sun-grown plants have leaves with a lower tions. area, and which contain smaller specific When a forest behavior is em- than species’ chloroplasts shade-grown plants. pirically known, then it is usually possible Most of the responses described above to explain its photosynthetic capacities and are also applicable to trees, but the re- its morphology in terms of shade tolerance sponses of trees may be modified because (see, for example, Tsel’Niker, 1977; Baz- of their variable social status within a forest. zaz and Carlson, 1982; McMillen and For example, sun-shade responses within McClendon, 1983, among others). How- a tree may be different from sun-shade re- ever, when there is no empirical knowl- of the same sponses of seedlings species edge for a given species of its ecology or (Leverenz and Jarvis, 1980). It is also im- its silvicultural behavior, is it possible to de- portant to investigate sun-shade adapta- duce the degree of shade tolerance simply tion at the genotype level. from its photosynthetic capacities and its The sun-shade responses can be ex- reactions to experimental variations in light pressed by different degrees of shade tol- environment? This question is fundamental erance, and have long been used by for a wide variety of forest species which make up the tropical rain forest and about to answer the following question. Can a which we have almost no silvicultural species’ shade tolerance be predicted by knowledge. the photosynthetic response of seedlings In unmanaged tropical rain forests, the of that species grown under a range of environments? presence of a species in a particular place light at a particular time is almost always condi- tioned by its response to light. Of course, it PLANT MATERIAL also depends on other factors, such as seed availability, dispersal and germination AND STUDY METHOD of these seeds, competition and allelo- pathy processes, or edaphic conditions. studied This is the way the species’ succession cy- Species cle is developed from pioneer species, and seedling growth conditions which require high quantities of light, which the are generally shade intolerant, and which The seedlings used for experiment were from the rain forest of Guade- colonize open space, to species of stable sampled tropical loupe, French West Indies, in the Caribbean Is- adult stands, which are more generally lands. They come from the area called "Débau- shade tolerant when young (Whitmore, chée" (Ducrey, 1986) at an elevation of 250 m. 1978; Rollet, 1983). The opening of these Mean temperatures were 23°C for January and stable stands by natural wind-fallen wood 26°C for July. Mean annual rainfall was more or partial harvesting, creates gaps whose than 3 000 mm. There was a short dry season from to where rainfall size (ie light conditions as well) partially January April, monthly was than 100 mm. determines which species will be able to always greater establish themselves. The 7 species studied were evergreen dominant and co-dominant trees from middle and The problem of species succession and late successional cycle of the Guadeloupe’s rain shade tolerance has been posed for the forest. Dacryodes excelsa Vahl, Amanoa cari- Guadeloupe tropical rain forest where we baea Kr and Urb, and Podocarpus coriaceus LC conducted silvicultural studies on 7 com- Rich are late successional, shade-tolerant spe- mercially interesting species. The objective cies. Simaruba amara Aubl and Richeria grandis Vahl are mid-successional, shade-intolerant was to favor natural of these regeneration species. Byrsonima coriacea is present in mid- species (Ducrey and Labbé, 1985). The and late succession, whereas Symphonia globu- study of the seedlings in relation to the in- lifera L, a wet soil specialist, is a late succes- tensity of regeneration fellings gave us pre- sional species. However the shade reaction of liminary information about light response of these 2 species is not well known. the species whose regeneration was in- The seedlings were generally aged 1 yr, har- duced by silvicultural treatment (Ducrey vested from the forest margin in January 1981, and Labbé, 1986). To improve this infor- and transplanted to 9-I pots filled with soil from the upper horizon of the forest floor. The pots mation, we cultivated from 7 for- seedlings were placed under a forest canopy to ensure a est under semi-controlled species light better recovery. After 3 months, the pots were conditions under differently shaded tunnel transferred to tunnel greenhouses, 15 m long greenhouses. In a previous article (Ducrey, and 6 m wide, covered with shade cloth trans- 1992), we studied the morphological varia- mitting the amount of light desired. The same tions of the leaf system in relation to procedure was applied to all species except P coriaceus whose were all placed in shade. In this we shall examine the seedlings paper, the same tunnel in March 1981 and then distrib- of the photosynthetic response seedlings uted to the different tunnels in January 1982, of these 7 species cultivated under 5 differ- and A caribaea which was started 1 yr later in ent shade environments. We shall also try March 1982. The seedlings were regularly wa- tered twice a week. No fertilizer was used dur- ential gas analyser of carbon dioxide (ADC mod- ing the experiment. el) which measured the difference in CO2 con- centration between the reference circuit and The seedlings were separated into 5 treat- the ments: 4 treatments under plastic tunnels and 1 measured circuit. The temperature was set be- open air, full sunlight treatment. The 4 tunnel tween 25 and 27°C using a water cooling sys- shelters were covered with reinforced transpar- tem where the measurement chamber was sub- ent PVC to protect against rainfall. Three of merged in a tank containing cooled water. them were shaded with different black neutral Relative humidity of the air was maintained be- shade screens in order to obtain various shade tween 70 and 90% by bubbling air into a water conditions. Finally, global radiation measure- flask maintained at the temperature of the de- ments with Li-Cor, Li 200 pyranometers indi- sired dew point. cates 6.4% light under tunnel I, 11.4% light un- Lighting was achieved using a mobile stand der tunnel II, 18.8% light under tunnel III, and of tungsten-halogen quartz lamps with a unit 54.3% light under tunnel IV. power of 1 000 W. Photosynthetic active radia- Table I shows climatic data under tunnel tion was measured with a Li-Cor, LI 190 quan- shelters. These were opened and oriented in tum sensor. Four light levels were used: 28 and the direction of prevailing winds. The tempera- 56 μmol m-2 s-1 for low light; 368 and 632 μmol ture and humidity of the air under the tunnels m-2 s-1 for saturating light. A few measurements were the same as those in the open-air treat- were also taken at 924 μmol m-2 s-1, but the re- ment (meteorological data measured with a sults were always less than or equal to those at weather station), except for tunnel IV whose 632 μmol m-2 s-1. We thus considered that satu- maximum temperatures were slightly higher ration was reached between 368 and 632 μmol than in the others. In fact, the shade under this m-2 s-1, and we did not use the data for 924 tunnel was created using only a reinforced trans- μmol m-2 s-1. Gas exchange measurements parent plastic cover which caused a more signifi- were made first in darkness to calculated dark cant warming effect. Because of only small cli- respiration and then with increasing light levels. matic differences between experimental The area and dry weight of the leaves stud- treatments and additional we can con- watering, ied were also calculated. This made it possible sider that is the variable between the light major to calculate photosynthesis per unit of leaf area 5 treatments. and per unit of leaf dry matter, and to determine the specific leaf area (ratio between leaf area and leaf dry weight) of the leaves studied (table III). Measurements of net photosynthesis Dark respiration and photosynthesis in low light made it possible to determine the initial of the net curves Photosynthesis measurements took from slope photosynthesis-light place which is called and the end of October to the end of December apparent quantum yield which approximates to the quantum of the 1982. The seedlings were kept under the experi- yield leaf (number of moles of assimilated per mental light conditions for close to 2 yr (except CO2 mole of photons absorbed the that for A caribaea and P coriaceus which were kept by leaf) except only incident flux was measured. for only 1 yr) and all the leaves measured were photon density initiated and grown under the treatment condi- Light-saturated net photosynthesis was then tions. These leaves could be considered as be- calculated as an average of photosynthesis val- ing completely acclimated to the experimental ues recorded at 368 and 632 μmol m-2 s-1. In light conditions. Measurements were made on the same way, light-limited net photosynthesis is fully developed leaves. The mean size of the an average of photosynthesis values recorded seedlings used in photosynthesis measure- at 28 and 56 μmol m-2 s-1. ments is shown in table II. An average of 4 seedlings per tunnel and per The measurements of net photosynthesis species were used, representing a total of 147 were carried out in the laboratory on attached plants and 147 net photosynthesis-light curves. leaves or branches placed in a ventilated cham- The 4 variables defining the 147 net photosyn- ber, perpendicular to the light source. The thesis-light curves carried out for this study were measurement of carbon dioxide exchange was analysed by an analysis of variance with 1 fac- made in an open system using an infrared differ- tor, Tunnel, for each species. Differences between tunnels were set out with a Duncan’s test of these results, we combine the net photo- of multiple mean comparisons. Relationships synthesis-light curves for each species in between these 4 variables and relative light in- dense shade (tunnel I, 6% relative light intensity were analysed by linear regression, spe- tensity) and full sunlight (tunnel V, 100% cies by species, on raw data. RLI) in figure 1.

RESULTS Light-saturated net photosynthesis The results shown in table IV represent data recorded per unit of leaf area; those For plants grown in full sunlight, light- in table V show data recorded per unit of saturated photosynthesis recorded per unit dry matter. To facilitate the interpretation of leaf area was the highest for S amara

(7.9 μmol m-2 s-1) and the lowest for D ex- dry matter units, the species ranking was celsa (3.4 μmol m-2 s-1). Photosynthesis approximately the same. The small recorded per unit of dry matter was then amount of change was due to small differ- 65 nmol g-1 s-1 for S amara and 35 nmol ences in specific leaf area between spe- g-1 s-1 for D excelsa. The other species cies, for plants grown in full sunlight. had intermediate values. Whether photo- For plants grown in shady conditions, synthesis was recorded per leaf area or light-saturated photosynthesis recorded per unit of leaf area showed a general lower for plants grown in full sunlight than trend, decreasing from light shade (tunnel for plants grown in shady conditions. All IV, 54% RLI) to heavy shade (tunnel I, 6% species considered together, apparent RLI). Some species, like S amara, reacted quantum yield was slightly, but statistically more strongly than others to changes in greater for shaded plants (47-49 mmol light regime, as shown in figure 1. An mol-1) than for sun-grown plants (42 mmol opposite trend was found when photosyn- mol-1). thesis was recorded in dry matter units. Photosynthesis is then higher for plants under heavy shade (tunnels I, II and III, Dark respiration 6-19% RLI) than for plants under light shade (tunnel IV, 54% RLI) or in full sun- Leaf dark respiration was very low for A light. caribaea and very high for P coriaceus, R grandis and S amara, whether it was expressed on dry-weight or leaf-area ba- Light-limited net photosynthesis sis. Compared with apparent quantum yield, these data seem to indicate that species with a high apparent quantum For plants grown in full sunlight, light- yield also had a high dark respiration and limited photosynthesis on a leaf area basis vice versa. Only P coriaceus seems to be was the highest for S globulifera (1.8 μmol an and had a dark m-2 s-1) and the lowest for D excelsa exception high respiration along with a low apparent quantum (0.8 μmol m-2 s-1). Photosynthesis record- yield. All species considered together, res- ed per unit of dry matter was then 23 nmol piration was lowest in tunnels II and III, s-1 for S globulifera and 9 nmol s-1 g-1 g-1 and in shade and full sun- for D excelsa and P coriaceus. The other highest strong light. species had intermediate values. For plants grown under different shade treatments, light-limited photosynthesis on Influence of growth conditions a leaf-area basis decreased from deep and leaf characteristics shade (tunnel I, 6% RLI) to light shade IV, 54% the lowest values be- (tunnel RLI), It was interesting to relate the results ob- ing encountered in full sunlight. At a spe- tained in the different tunnels to light condi- cies level, this trend was not true always tions and specific leaf area. Figure 2 because of data This trend high variability. shows that when all the species are con- appeared clearly for most of the species sidered together, maximum photosynthesis when was recorded photosynthesis per per leaf area unit increased with relative unit of dry matter. light intensity during growth, at first rapidly until the relative light intensity was near 20% (tunnel III), then much more slowly Apparent quantum yield (fig 2a). On the other hand, it decreased regularly when specific leaf area increased ie with shade. For plants grown in full sunlight, apparent (fig 2b), increasing quantum yield was the highest for S amara Apparent quantum yield decreased with (58 mmol mol-1) and R grandis (54 mmol relative light intensity (fig 2c) and in- mol-1) and the lowest for D excelsa (23 creased with specific leaf area (fig 2d). Its mmol mol-1). These values were slightly variation was the reverse of that found for maximum net photosynthesis. This phe- According to specific leaf area, species nomenon has frequently been observed may be ranked from the most plastic to the when comparing shade and sun pheno- least plastic species: R grandis, S amara, types. B coriacea, D excelsa, A caribaea, S glob- Linear regressions to explain specific ulifera and P coriaceus. According to light- S amara was leaf area, light-saturated photosynthesis, saturated photosynthesis, light-limited photosynthesis and apparent found to be the most plastic species. It was R quantum yield as a function of relative light followed, in decreasing order, by gran- intensity, were calculated for each species dis, B coriacea and P coriaceus. D excelsa (table VI). Most of the regressions were and A caribaea both had "a" coefficients statistically significant at a 5% level, except not significantly different from zero, where- for apparent quantum yield. The "a" as S globulifera reacted negatively to in- coefficient in the regression equation ex- creasing relative light intensity. For each presses, for a given trait, the species plas- species, light-limited photosynthesis and ticity in reaction to light conditions during apparent quantum yield decreased with in- growth. creasing light intensity.

DISCUSSION AND CONCLUSION close to 5 μmol CO2 m-2 s-1 for maximum net photosynthesis and 0.6 μmol CO2 m-2 s-1 for dark respiration. Large differences between Comparison species in shade tolerance can be seen between these species, but the knowledge of their For the 7 species studied in Guadeloupe, photosynthetic potential is not sufficient to maximum net photosynthesis in full sun- rank them according to an increasing order light was between 3.4 μmol m-2 s-1 for D of shade tolerance. The understory spe- excelsa and 7.9 μmol m-2 s-1 for S amara. cies have a photosynthesis close to 2 μmol The var- corresponding respiration values CO2 m-2 s-1 and a respiration close to 0.2 ied from 0.15 to 0.64 μmol m-2 s-1 de- μmol CO2 m-2 s-1. pending on the species. Our results are These results give a idea of the compared (table VII) with the results of good of tropical rain- others studies including those by Stephens photosynthetic potential forest are, in fact, close and Waggoner (1970), Bazzaz and Pickett species. They very to those for forest found (1980), Koyama (1981), Oberbauer and temperate species Bazzaz who Strain (1984), Langenheim et al (1984), by (1979), gives photosynthetic of 10.0 for at the and Thompson et al (1988). potentials species beginning of the succession, 5.7 for spe- Pioneer trees in the early successional cies at the end of succession, and 2.2 for stages or young secondary formations gen- understory species. erally have a high photosynthetic potential (14 μmol CO2 m-2 s-1) along with a high dark (0.8 m-2 s-1). respiration μmol CO2 Comparison of sun Stable forest formations in the late succes- and shade phenotypes sional species stages are composed of 3 main layers: an upper layer including emergent and dominant trees; a middle For the 7 species studied, apparent layer composed of average-sized trees quantum yield was higher for shade-grown which completely close the forest canopy; plants (shade phenotypes) than for and a lower layer composed of understory sun-grown plants (sun phenotypes). On species. the other hand, light-saturated photosyn- Among the emergent trees both "sun" thesis on a leaf-area basis was higher for sun than for shade species which are shade intolerant and phenotypes pheno- for A caribaea and S "shade" species which are more or less tol- types, except globulif- erant to shade can be found. Sun species era. have an almost identical response to that Similar results were reported by Logan of pioneer species (photosynthesis: 11 (1970) for Betula alleghaniensis, by μmol CO2 m-2 s-1 and dark respiration: 1.0 Tsel’Niker (1977) for 5 forest species, by μmol CO2 m-2 s-1). An analogy can be Duba and Carpenter (1980) for Platanus made between these 2 groups as the occidentalis, by Bazzaz and Carlson emergent sun species appear very early in (1982) for 12 herbaceous and shrub spe- the first successional stages as do the pio- cies and by Nygren and Kellomaki (1983) neer species, but they have a much longer for 10 forest species. All the species stud- life than the latter which is why they can be ied by these authors belong equally to the found in the late successional stages. early and late successional stages and The results for shade species from the thus both shade-tolerant and shade- upper layer and from the middle layer are intolerant species can be found.

The commonly accepted explanation for er than that of sun phenotypes. Similar re- these results is that shade and sun pheno- sults were also found by Gatherum et al types are well adapted to the light environ- (1963) for 3 different forest species. Logan ment in which they grow and that the light and Krotkov (1969) interpreted these re- level at which photosynthesis reaches its sults by saying that when plants of this saturation plateau corresponds to the light type photosynthesize under the same light conditions most commonly found by the conditions, plants grown under low light plant in its natural environment (Tsel’Niker, use light more efficiently than those grown 1977). Under these conditions, shade in full sunlight. phenotypes have higher quantum yield The 2 main types of results for shade and lower light-saturated photosynthesis. and sun phenotypes are contradictory and For A caribaea, we found no effect of many references could be quoted for each light growth conditions on light-saturated point of view. Logan and Krotkov (1969) photosynthesis, whereas light-saturated tried to provide an explanation. They hy- photosynthesis of S globulifera was higher pothesized that the photosynthetic mecha- for shade-grown plants than for sun-grown nisms of tolerant species are better adapt- plants. Similar results have also been ed to low rather to high light habitats, and found by various authors. For Tilia ameri- conversely, that the photosynthetic mecha- cana, Bazzaz and Carlson (1982) found nisms of intolerant species are better that sun and shade phenotypes had identi- adapted to high rather than to low light cal rates of photosynthesis. For Acer sac- habitats. This theory involves the degree of charum, Logan and Krotkov (1969), and adaptation to shade and is not entirely con- Bazzaz and Carlson (1982) found that pho- vincing as both types of response can be tosynthesis of shade phenotypes was high- found in tolerant and intolerant species. When we expressed photosynthesis on plant sample from the same experiment dry leaf matter basis, it was found that, for (Ducrey, 1992). all species, the highest values correspond- From the regressions between light- ed to shade phenotypes and the lowest to saturated photosynthesis and relative light sun table phenotypes (see VI). Photosyn- intensity, an index of photosynthetic plas- thesis unit can be consid- per dry weight ticity may be defined. S amara appears as ered to be the of the leaf product specific the most plastic species. The following are area by photosynthesis per unit leaf area. then found in decreasing order: R grandis, For the species studied, photosynthesis B coriacea, P coriaceus, D excelsa and A per unit leaf area decreased with shade caribaea. S globulifera reacted negatively while specific leaf area increased, and the to increasing light intensity. final result, as we have seen, was an in- There is a good agreement between the crease with shade of photosynthesis per different indexes of plasticity, the pre- unit dry weight. This result depends on the sumed degree of shade tolerance of degree of variation between shade and Guadeloupe species and their place in the sun for the 2 parameters studied. Thus, species’ succession cycle in tropical rain any result is possible and would depend forests. Simaruba amara and Richeria on the morphological and photosynthetic grandis are the most plastic species from a plasticity of the species studied. morphological and photosynthetic point of view. They are early successional species, but not really pioneer species, and were Photosynthetic plasticity considered as light-intolerant species (Du- and shade adaptation crey and Labbé, 1986). Byrsonima coriacea is also a plastic species. This makes it Bazzaz and Carlson (1982) introduced the possible to rank this species among shade notion of photosynthetic flexibility (or plas- intolerant species even though little was ticity) to interpret the range of variation, previously known about its forest behavior. from dense shade to full sunlight, in The 3 species Podocarpus coriaceus, Da- parameters defining the photosynthetic ac- cryodes excelsa and Amanoa caribaea had tivity of a given species. They concluded in low morphological and photosynthetic plas- their study that photosynthetic flexibility ticity indexes. They are more or less shade was higher for early pioneer successional tolerant and are late succession species. A species, average for intermediate species special emphasis should be made on Sym- and lowest for late successional species. phonia globulifera, a species with very low and whose The "a" coefficients from table VII may plasticity, light-saturated photo- decreased with relative be considered as indicators of species synthesis increasing plasticity. From the regressions between light intensity. This species should be a strict "shade but it is also a wet specific leaf area and relative light intensi- species", soil so it be a dominant ty, an index of morphological plasticity specialist, may species in the late succession may be defined. According to this index, R stages. grandis and S amara are the 2 most plas- This work has made it possible to gain a tic species, immediately followed by B cori- basic knowledge about the photosynthetic acea; D excelsa and A caribaea are less potentials of the main commercially inter- plastic; and S globulifera and P coriaceus esting forest species from the Guadeloupe are the least plastic species. These results tropical rain forest. It has also character- agree with those obtained on a greater ized the shade and sun phenotypes of these species from the point of view of Ducrey M (1992) Variation in leaf morphology their photosynthetic activity. However, and branching pattern of some tropical rain studying only photosynthetic activity forest species from Guadeloupe (French West Indies) under semi-controlled light con- seems to be insufficient to determine the ditions. Ann Sci For 49 (6), 553-570 degree of shade tolerance. 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