Leaf structure of syzygium spp. (myrtaceae) in relation to site affinity within a tropical rain forest

Gamage, Harshi K., Ashton, Mark S. and Singhakumara, B. M. P. (2003) Leaf structure of syzygium spp. (myrtaceae) in relation to site affinity within a tropical rain forest. Botanical Journal of the Linnean Society, 141 3: 365-377. doi:10.1046/j.1095-8339.2003.00138.x


Author Gamage, Harshi K.
Ashton, Mark S.
Singhakumara, B. M. P.
Title Leaf structure of syzygium spp. (myrtaceae) in relation to site affinity within a tropical rain forest
Journal name Botanical Journal of the Linnean Society   Check publisher's open access policy
ISSN 0024-4074
Publication date 2003-03
Sub-type Article (original research)
DOI 10.1046/j.1095-8339.2003.00138.x
Open Access Status
Volume 141
Issue 3
Start page 365
End page 377
Total pages 13
Place of publication London, U.K.
Publisher The Linnean Society of London
Language eng
Subject 0607 Plant Biology
Formatted abstract
This study examined four species  of Syzygium (S. firmum, S. makul, S. operculatum, S. rubicundum) Myrtaceae, a tree genus that dominates the canopy of rain forests of south-west Sri  Lanka. Syzygium spp. occupy differing habitats with relation to succession and forest topography. We examined differences in leaf morphology and physiology in response to amount of shade, an important environmental variable affecting Syzygium distribution within the forest. To study change in leaf structure and physiology, environmental shelters were constructed simulating forest shade that differed in quality, quantity and duration. Seedlings were exposed to: (i) 0% shade (full sun, FS), red : far red (R : FR) ratio 1.27; (ii) 65% shade (large opening, LO) with direct sunlight similar to the centre of a large canopy opening, R : FR ratio 1.27; (iii) 82% shade (small opening, SO) with direct sunlight similar to the centre of a small canopy opening, R : FR ratio 1.27; (iv) 58% uniform light shade (LS) with a quality similar to the outside edge of a large canopy opening, R : FR ratio 1.05; (v) 85% uniform medium shade (MS) with a quality similar to the inside forest edge of a large canopy opening, R : FR ratio 0.97; (vi) 99% uniform deep shade (DS) similar to that of the forest understorey, R : FR ratio 0.23. The shelters were constructed in a large open area at the field station of the Sinharaja World Heritage site, Sri Lanka. Seedlings of each species were grown for two years in their respective shade treatments before physiological, morphological and anatomical measurements were made on leaves. Variation in leaf structure and physiology between the species was associated with differences in shade-tolerance and water-use. All species increased in photosynthesis rates and dimensions in leaf structure (leaf blade and cuticle thickness, stomatal density, thickness of upper and lower epidermis, and thickness of palisade mesophyll) with decrease in shade. In contrast, stomatal conductivity was highest in the DS (99% shade) treatment. Leaves of Syzygium firmum were thickest and largest in area. S. firmum also had highest photosynthesis in the SO (82% shade) treatment. S. firmum was the most shade-tolerant of all species: it grows well in low shade and its leaf structure suggests it to be the most conservative in water-use of the Syzygium spp. In the forest S. firmum can persist in the forest shade as established seedlings, but grows best within canopy openings of late-seral rain forest. Leaves of S. operculatum were thinnest but had highest stomatal densities of the four species. S. operculatum is considered shade-intolerant, with a leaf structure suggesting it to be prone to desiccation, and by implication susceptible to drought. S. operculatum is found along streams within early seral rain forest habitat, often originating on stream banks after land clearance for cultivation. In the FS (0% shade) treatment, S. rubicundun had highest photosynthesis rates and greatest number of leaves but smallest leaf area of the Syzygium species. S. rubicundum is more shade-intolerant but more efficient in water-use than S. operculatum. S. rubicundum is a mid-seral canopy tree of the midslope stands that are thought to have originated after catastrophic windthrows or swidden cultivation. The leaf physiology and structure of S. makul suggests it to be both moderately shade-tolerant and conservative in water-use. It is the most widely distributed Syzygium species across the topography of late-seral rain forest. We suggest forest disturbance and hydrology are important environmental factors that influence distribution of Syzygium species across the topography. Results from this study contribute to a body of knowledge suggesting that canopy tree species of rain forests in south-west Sri Lanka have discrete affinities to topography and differences in successional status, and that adaptations in leaf structure and physiology are indicative of such phenomena.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 141, 365–377. 
Keyword Leaf morphology
Mixed-dipterocarp forest
Photosynthesis
Physiology
Plasticity
Shade
Sinharaja
Sri Lanka
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

 
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