by Jack B. Fisher, Usher Posluszny, and David W. Lee

in International Journal of Plant Sciences 163.2, 2002

The liana Artabotrys hexapetalus (L.f.) Bhand., which is widely planted in the Tropics and native to African rain forests, produced new reiterations (new leader shoots) normally and after damage induced by Hurricane Andrew (August 24, 1992). In each new orthotropic shoot, there is a gradient in lateral branch structures from basal thorns, to vegetative leafy branches, to distal leafy flowering branches. We noted that reiterations developing in shade had more thorns than similar reiterations developing in full sun. Tents with clear (66% photosynthetically active radiation [PAR]) and shaded plastic film (12%–14% PAR) were placed over nodes when the axillary buds began to expand to produce reiteration shoots. After 2 mo of growth inside the tents and in the open, the types of lateral outgrowths (thorn vs. branch) were recorded. Shoots in spectrally neutral shade (red to far red of full sun) and spectrally altered shade (red to far red of canopy shade) produced significantly more thorns at the lower nodes of the shoots as compared to those in full sun. Shoots in control clear plastic tents were the same as those in full sun. We conclude that the fate of lateral bud development is controlled by irradiance (light level) but not by light quality. Increased thorn production in shade could be advantageous to plants growing in the deep shade of rain forests. Thorns in the self-shaded regions of the plant, and well below the forest canopy, could aid in protection from herbivory and in climbing by acting as hooks.

by David W. Lee and Jennifer H. Richards

in The Biology of Vines edited by Francis E. Putz, 2001

All plants pass through a series of developmental changes from seedling to reproductive age. In may plants the shifts in development are subtle, involving internode distance or small changes in leaf size and shape. In others the changes are profound, so much so that early and late stages have been identified as separate species Goebel (1900) recognized these differences in the degree of developmental change, designating the former as homoblastic and the latter as heteroblastic. Since Goebel’s treatment, the concept of heteroblastic development has been extended to species in which the juvenile to adult transition is more gradual, which includes the majority of plants (Allsopp, 1965), and the term has been applied to developmental changes in floral form in the reproductive phase (Lord, 1979).

by David W. Lee, Steven F. Oberbauer, Paulette Johnson, Baskaran Krishnapilay, Marzalina Mansor, Haris Mohamad, and Son Kheong Yap

in American Journal of Botany 87.4, 2000

ABSTRACT

We studied the development of leaf characters in two Southeast Asian dipterocarp forest trees under different photosynthetic photon flux densities (PFD) and spectral qualities (red to far-red, R:FR). The two species, Hopea helferi and H. odorata, are taxonomically closely related but differ in their ecological requirements; H. helferi is more drought tolerant and H. odorata more shade tolerant. Seedlings were grown in replicated shadehouse treatments of differing PFD and R:FR. We measured or calculated (1) leaf and tissue thicknesses; (2) mesophyll parenchyma, air space, and lignified tissue volumes; (3) mesophyll air volumes (Vmes/Asurf) and surfaces (Ames/Asurf); (4) palisade cell length and width; (5) chlorophyll/cm2 and a/ b; (6) leaf absorption; and (7) attenuance/absorbance at 652 and 550 nm. These characters varied in response to light conditions in both taxa. Characters were predominantly affected by PFD, and R:FR slightly influenced many characters. Leaf characters of H. odorata were more plastic in response to treatment conditions. Characters were correlated with each other in a complex fashion. Variation in leaf anatomy is most likely a consequence of increasing leaf thickness in both taxa, which may increase mechanical strength and defense against herbivory in more exposed environments. Variation in leaf optical properties was most likely affected by pigment photo-bleaching in treatments of more intense PFD and was not correlated with Amax. The greater plasticity of leaf responses in H. odorata helps explain the acclimation over the range of light conditions encountered by this shade-tolerant taxon. The dense layer of scales on the leaf undersurface and other anatomical characters in H. helferi reduced gas exchange and growth in this drought-tolerant tree.

by David W. Lee, S. F. Oberbauer, B. Krishnapilay, and M. Mansor

in Proceedings of 6th Round Table Conference on Dipterocarps in Bangalore, India, February 1999

ABSTRACT

Hopea helferei and H. odorata grow in evergreen and semi-deciuous forests of Indochina, as far south as northern Malaya. H. odorata grows in dense forest on stream margins, and H. helferei on well-drained slopes. We examined developmental responses of seedlings to irradiance (3%, 12%, 40% and 100% of photosynthetically active radiation, PAR) and spectral quality (R:FR, red:far-red quantum ratios of 0.25 and 1.25). Besides observing growth, allocation, architecture and gas exchange characteristics we examined differences in leaf structure in particular detail. Seedlings of H. odorata grew most rapidly under shade and were the most plastic in response to light treatments. Irradiance and spectral quality influenced characters differently in both species, although leaf anatomical variables responded less and were not affected by R:FR. However, leaf structure (affecting mesophyll surface area), along with undersurface scales in H. helferei, help explain the lower maximum photosynthesis and growth rates of this more drought-tolerant taxon. The differences in the light-influenced seedling traits between these very closely related taxa suggest that such characters have evolved rapidly and are not likely to be phylogenetically conserved.

by David W. Lee, S. Oberbauer, K. Baskaran, M. Mansor, H. Mohamad and S.K. Yap

in Journal of Tropical Forest Science 11.1, 1999

Jelutong [Dyera costulata (Miq.) Hook. f., Apocynaceae] is a long-lived pioneer tree that eventually becomes a giant emergent in the rain forests of Peninsular Malaysia and Sumatra. We conducted trials to determine responses of growth, morphology, leaf anatomy, architecture and physiology of jelutong seedlings to different irradiances (photon flux density, 400-700 nm, PFD) and spectral qualities (red/far-red quanta, or R:FR). Seedlings were grown in six replicated treatments: (1) direct sunlight and 1.25 R:FR; (2) 40% solar PFD and 1.25 R:FR; (3) 13% PFD and 1.25 R:FR; (4) 10% PFD and 0.25 R:FR; (5) 3% PFD and 1.25 R:FR; and (6) 3% PFD and 0.25 R:FR. Based on dry mass increments, final height, collar diameter, architecture, and maximum photosynthesis, seedlings grew most rapidly in the 40% sunlight treatment, and varied little in response to low-and medium-PFD environments. Spectral quality did not influence growth and development very much, but low R:FR reduced leaf allocation and area, and reduced growth as mass/day. Leaf anatomy and physiology were influenced exclusively by PFD. These results are consistent with observations of jelutong seedlings being shade-tolerant, slow growing, stunted in direct sunlight, and dramatically different to their behavior in later developmental stages and that of short-lived pioneers.

by David W. Lee with S. Oberbauer, K. Baskaran, M. Mansor, H. Mohamad and S.K. Yap

in Oecologia 110, 1997

ABSTRACT

Seedling developmental responses to understory shade combine the effects of reductions in irradiance and changes in spectral quality. We studied the seedling development of two Southeast Asian dipterocarp trees in response to differences in irradiance (photosynthetic photon flux density, PPFD) and spectral quality (red to far-red ratio, R:FR). The two species, Hopea helferei and H. odorata, are taxonomically closely related but differ in their ecological requirements; H. helferei is more drought-tolerant and typically grows in more open habitats. Seedlings were grown in six different replicated shadehouse treatments varying in percentage of solar PPFD and R:FR. The two species differed in the influence of light variables on most seedling characters, particularly for final height, internode distance, branch/trunk internodes, stem length/mass, leaf area/ stem length, petiole length, and growth/mol of photons received. Most of the characters in both taxa were primarily influenced by PPFD, but spectral quality also influenced some characters – more so for H. odorata. The latter species grew more rapidly, particularly in the low PPFD treatments, and its leaves were capable of higher photosynthesis rates. However, growth in H. helferei was not reduced in direct sunlight. The growth of this taxon may be constrained by adaptations, particularly in leaves, for drought tolerance.

by David W. Lee, S.F. Oberbauer, B. Krishnapillay, M. Marzalina, M. Haris & S. K. Yapin

in S. Appanah and K.C. Khoo, eds. Proceedings of the Fifth Round-Table Conference on Dipterocarps, 1996

Seedling developmental responses to understory shade are the combination of reductions in irradiance and changes in spectral quality. We studied the seedling development of five dipterocarps, Dryobalanops aromatica, Hopea helferei, H. odorata, H. wightiana, and Shorea singkawang under varying intensity (photon flux density, PFD) and spectral quality (red to far-red, R:FR). Seedlings were grown in replicated shadehouse treatments: (1) 40% solar PFD and 1.25 R:FR; (2) 12% PFD and 1.25 R:FR; (3) 12% PFD and 0.25 R:FR; (4) 3% PFD and 1.25 R:FR; and (5) 3% PFD and 0.25 R:FR. Species differed in the influence of light variables on seedling (1) total height; (2) internode distance; (3) branch to trunk internodes; (4) stem length/mass; (5) leaf area/stem length; (6) percent allocation to leaf, stem and root mass; (7) specific leaf mass; (8) mean leaf area; (9) leaf thickness; (10) petiole length; and (11) stomatal density. The simple factorial design of treatments 2-5 allowed a two-way ANOVA and the calculation of coefficients of determination of the treatment effects. Most of the characters in most taxa were primarily influenced by light intensity, but spectral quality also influenced characters in many cases. Recommendations concerning seedling shade tolerance for silviculture or nursery practice may need revision if they are based on shade trials using spectrally neutral shade fabrics or slat houses. The patterns of morphological responses in reduced PFD and R:FR also help to explain how shade tolerances of the seedlings of rain forest trees vary in a continuous manner. Future research on the effects of shading on tree seedling development and ecology must consider the potential influence of changes in spectral quality under canopy shade.

by David W. Lee, K. Baskaran, M. Mansor, H. Mohamad and S.K. Yap

in Ecology 77.2, 1996

ABSTRACT

Plant developmental responses to shade are the combination of reductions in photosynthetic photon flux density (PPFD) and changes in spectral quality (reductions in the quantum ratio of red to far-red band widths, R:FR). We studied the seedling development of six Asian tropical forest trees, Dryobalanops aromatics, Endospermum malaccense, Hopea wightiana, Parkia javanica, Shorea singkawang, and Sindora echinocalyx under varying PPFD and R:FR. Seedlings were grown in replicated shadehouse treatments (1) 40 solar PPFD and 1.25 R:FR; (2) 11% PPFD and 1.25 R:FR; (3) 11% PPFD and 0.24 R:FR; (4) 3% PPFD and 1.25 R:FR; and (5) 3% PPFD and 0.23 R:FR. Species differed in the influence of light variables on seedling (1) total height; (2) internode distance; (3) branch to trunk internodes; (4) stem length/mass; (5) leaf area/stem length; (6) percent allocation to leaf, stem and root mass; (7) specific leaf mass; (8) mean leaf area; (9) leaf thickness; (10) petiole length; and (11) stomatal density. The simple factorial design of treatments 2-5 allowed a two-way ANOVA and the calculation of coefficients of determination of the treatment effects. The characters in most taxa were primarily influenced by light intensity, but spectral quality also influenced characters in many cases. The taxa that responded most strongly to the light treatments were the most shade-intolerant: E. malaccense and P. javanica; the former species responded strongly to R:FR, particularly in stem mass allocation and leaf area/stem length. The four taxa with moderate-to-extreme shade tolerance varied considerably in responses of individual characters to R:FR and PPFD. The patterns of morphological responses to reduced R:FR and PPFD help explain how the shade tolerances of the seedlings of rain forest trees vary in a continuous manner. Recommendations concerning seedling shade tolerance for sylviculture of nursery practice may need revision if they were based on shade trials using spectrally neutral shade fabrics or slat houses. Future research on the effects of shading on tree seedling development and ecology must consider the potential influence of changes in spectral quality under canopy shade.

by David W. Lee, K. Baskaran, M. Mansor, H. Mohamad and S.K. Yap

in Journal of Tropical Forest Science 8.4, 1996

We studied seedling development of Gonostylus bancanus (ramin melawis, Thymeliaceae) in response to shade conditions, to learn about the tree’s functional ecology. Shadelight compromises reuctions in solar irradiance (photosynthetic photon flux density, 400-700 nm, or PFD) and changes in spectral quality, as reductions in the red: far-red ratio (or R:FR). We studied the separate and interactive effects of PFD and R: FR on seedling development by growing them under six different replicated shadehouse treatment conditions. Seedlings grew least at low light levels and full sunlight. Seedling branching was not strongly affected by the light treatments, but stem robustness was promoted by PFD, and leaf area/stem length was decreased by low R:FR. Photosynthate allocation to leaves was low, and was primarily reduced by increasing PFD. Most of the effects on development were influenced by PFD; only internode length and leaf area/stem length were more influenced by R:FR. Seedlings on ramin malawis are intolerant of extreme shade and direct sunlight, growing most rapidly in partial shade, with daily percentages of 40% and more of full sunlight. Such seedlings are probably only at a competitive advantage in the inundated soils of their natural distribution.

by Daniel Bussion and David W. Lee

in American Journal of Botany 80.8, 1993

The developmental responses of plants to shade underneath foliage are influenced by reductions in irradiance and shifts in spectral quality (characterized by reductions in the quantum ratio of red to far-red wavelengths, R:FR). Previous research on the influence of shadelight on leaf development has neglected the reductions in R:FR characteristic of foliage shade, and these studies have almost certainly underestimated the extent and array of developmental responses to foliage shade. We have studied the effects of reduced irradiance and R:FR on the leaf development of papaya (Carica papaya L., Caricaceae). Using experimental shadehouses, replicates of plant growth in high light conditions (0.20 of sunlight and R:FR = 0.90) were compared to low light conditions (0.02 of sunlight) with either the spectral quality of sunlight (R:FR = 0.99) or of foliage shade (F:FR - 0.26). Although many characteristics, such as leaf thickness, specific leaf weight, stomatal density, palisade parenchyma cell shape, and the ratio of mesophyll air surface/leaf surface were affected by reductions in irradiance, reduced R:FR contributed to further changes. Some characters, such as reduced chlorophyll a/b ratios, reduced lobing, and greater internode length, were affected primarily by low R:FR. The reduced R:FR of foliage shade, presumably affecting phytochrome equilibrium, strongly influences the morphology and anatomy of papaya leaves.

by David W. Lee, Richard A. Bone, Sara L. Tarsis and David Storch

in American Journal of Botany 77.3, 1990

ABSTRACT

Thirteen shade-adapted rain forest species were compared with twelve sun-adapted tropical forest species for correlates to leaf optical properties (described previously in Amer. J. Bot. 73:1100-1108). The two samples were similar in absorptance of quanta for photosynthesis, but the shade-adapted taxa: 1) had significantly lower specific leaf weights, indicating a more metabolically efficient production of surface for quantum capture; 2) synthesized less chlorophyll per unit area; and 3) used less chlorophyll for capturing the same quanta for photosynthesis. The anatomical features that best correlate with this increased efficiency are palisade cell shape and chloroplast distribution. Palisade cells with more equal dimensions have more chloroplasts on their abaxial surfaces. This dense layer of chloroplasts maximizes the light capture efficiency limited by sieve effects. The more columnar palisade cells of sun-adapted taxa allow light to pass through the central vacuoles and spaces between cells, making chloroplasts less efficient in energy capture, but allowing light to reach chloroplasts in the spongy mesophyll. Pioneer species may be an exception to these two groups of species. Three pioneer taxa included in this study have columnar palisade cells that are extremely narrow and packed closely together. This layer allows little penetration of light, but exposure of the leaf undersurface may provide illumination of spongy mesophyll chloroplasts in these plants.

by David W. Lee

in Journal of Tropical Ecology 5.1, 1989

The canopy dynamics and light climates within a 20 by 60 m quadrat were studied in a disturbed moist deciduous forest near Bombay, India. A map was drawn of individual trees within the quadrat, the taxa were identified, and their phenology was followed from November 1984 to July 1985. The quadrat contained 14 species, the most common being Tectona grandis, Terminalia tormentosa, Butea monosperma, Mitragyne parviflora and Albizia procera. Some individuals were in leaf at all times, more so at the moister east end of the quadrat. In November at the end of the rainy season, light measurements documented percentages of total daily photosynthetic photon fluence (PPF) at 10.0% of full sunlight; 44% of this flux was due to sun-flecks whose duration was approximately 17% of the daytime hours. Values for six sites were similar to mid-day measurements along a 40 m transect, and consistent wit the 94% canopy cover of the sites, photographed with a fish-eye lens. The March dry season measurements revealed a more intense radiation environment (54% of solar PPF), and 59% of the photosynthetic photon flux density at mid-day along the transect. Canopy openings were increased to a mean of 59.4%. Light in the understorey in November was spectrally altered, with typical R:FR ratios of 0.30, compared to March values identical to those of sunlight, at 1.10.

by David W. Lee

in Journal of Tropical Ecology 4.3, 1988

ABSTRACT

Both light quantity and quality affect the development and autoecology of plants under shade conditions, as in the understorey of tropical forests. However, little research has been directed towards the relative contributions of lowered photosynthetic photon flux density (PPFD) versus altered spectral distributions (as indicated by quantum ratios of 660 to 730 nm, or R:FR) of radiation underneath vegetation canopies. A method for constructing shade enclosures to study the contributions of these two variables is described. Three tropical leguminous vine species (Abrus precatorius L., Caesalpinia bondicela Fleming and Mucuna pruriens (L.) DC.) were grown in two shade enclosures with 3-4% of solar PPFD with either the R:FR of sunlight (1.10) or foliage shade (0.33), and compared to plants grown in sunlight. Most species treated with low R:FR differed from those treated with high R:FR in (1) percent allocation to dry leaf weight, (2) internode length, (3) dry stem weight/length, (4) specific leaf weight, (5) leaf size, and (6) chlorophyll a/b ratios. However, these plants did not differ in chlorophyll content per leaf dry weight or area. In most cases the effects of low R:FR and PPFD were additional to those of high R:FR and low PPFD. Growth patterns varied among the three species, but both low PPFD and diminished R:FR were important cues in their developmental responses to light environments. This shadehouse system should be useful in studying the effects of light of the developmental ecology of other tropical forest plants.

by David W. Lee

in Biotropica 19.2, 1987

ABSTRACT

The spectral quality of radiation in the understory of two neotropical rainforests, Barro Colorado Island in Panama and La Selva in Costa Rica, is profoundly affected by the density of the canopy. Understory light conditions in both forests bear similar spectral characteristics. In both the greatest changes in spectral quality occur at low flux densities, as in the transition from extreme shade to small light flecks. Change in spectral quality, as assessed by the red : far-red (R:FR) ratio, the ratio of radiant energy 400-700: 300-1100 nm, and the ratio of quantum flux density 400-700:300-1100 nm, is strongly correlated with a drop in percentage of solar radiation as measurable by a quantum radiometer. Thus, by knowing the percentage of photosynthetic photon flux density (PPFD) in relation to full sunlight, it is possible to estimate the spectral quality in the forest at a particular time and microsite.

by Jennifer H. Richards and David W. Lee

in American Journal of Botany 73.12, 1986

The water hyacinth, Eichhornia crassipes Solms., displays marked foliar plasticity. A single plant can produce short leaves with swollen petioles or long leaves with narrow petioles. These different leaf types are found in different places in a water hyacinth population (Penfound and Earle, 1948; Musil and Breen, 1977; Richards, 1981; Watson, Carrier and Cook, 1982). Water hyacinths reproduce vegetatively by stolons, rapidly building up large, intertwined, free-floating mats. Plants at the edge of a mat produce small leaves with expanded petioles, while plants in the center of a mat produce long leaves with narrow petioles.

by David W. Lee and Rita Graham

in American Journal of Botany 73.8, 1986

The optical properties of the leaves of twelve tropical sun species and thirteen tropical extreme shade species were examined with an integrating sphere attached to a spectroradiometer. Measurements of diffuse reflectance and transmittance allowed calculations of absorptance, 350-1,100nm. Although some shade species absorbed higher percentages of quantum flux densities for photosynthesis (400-700nm, PPFD) than the. mean for the sun species, the sun and shade species as groups were not significantly different from each other: 90.2, S.D. 3.6% for shade species and 88.6, S.D. 2.4% for the sun species. The groups of species did not differ in total aboptance of energy 350-1,100 nm. Furthermore, the sun and shade species were identical in their shift of absorptance at wavelengths between 650 and 750 nm. The anthocyanic coloration of the leaf undersurfaces of two species polymorphic for this characteristic (Trionela hirsuta and Ischnosciphon pruinosus) is correlated with increased absorptance at the upper end of the action spectrum of photosynthesis. Although sun and shade species have similar optical properties, the energy investment (as documented by dry wt per unit area of leaf surface) is much less for the shade species.

by David W. Lee, K. P. Paliwal, K.A. Patel, and D. N. Sen

in Current Science 55.18, 1986

Leaves function as optical filters, selectively absorbing different wavelengths of electromagnetic radiation. Leaf optical properties vary, depending upon the environments in which the plants live. These properties must be measured if the photosynthetic efficiencies and the thermal properties and thus water relations of individual species are to be understood. Of the few species measured, none are native to the Indian subcontinent. Here we report the leaf optical properties of 22 taxa native to different vegetation types of India.

by R. A. Bone, D. W. Lee, and J. M. Norman

in Applied Optics 24, 1985

A ray tracing model has been developed to investigate the possible focusing effects of the convexly curved epidermal cell walls which characterize a number of shade-adapted plants. The model indicates that such focusing occurs, resulting in higher photosynthetic photon flux densities at certain locations within the leaf. It is postulated that there will be a corresponding increase in the rate of photosynthesis. In addition, leaf reflectance measurements indicate that this is generally less for the shade plants compared with sun species and would be advantageous in increasing the efficiency of energy capture. Either effect is important for plants which must survive at extremely low light levels.

by David W. Lee

in HortScience 20.1, 1985

ABSTRACT

A shade film is described which duplicates the spectral quality of light underneath foliage. The film should become an important tool for studying plant development, and it may have commercial applications.