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

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. rubic...

Variation in canopy structure, light and soil nutrition across elevation of a Sri Lankan tropical rain forest

“…Trends appear related to size of disturbance, stature of the forest, topographic position, and underlying geology and soil-weathering environment. Previous studies have demonstrated tree species differences in shade tolerance (Ashton, 1995;Ashton et al, 1995Ashton et al, , 2005Gamage et al, 2003); response to soil nutrition (Gunatilleke et al, 1996(Gunatilleke et al, , 1997Singhakumara et al, 2003) and aversion to drought (Ashton et al, 2005). The results from this study provide a stronger context for work conducted on Sri Lankan mixed dipterocarp forest on forest regeneration.…”

Morphological and physiological behaviour of sweet cherry ‘somaclone’ HS plants in field

“…1), which together with increased stomatal density gives it the distinguishing marks of a heliophilous plant (Lüttge et al 1997). The further plants get from the shadow condition the more these aspects are enhanced (Gamage et al 2003). HS supposed higher efficiency for light did not led to any significantly different performance in terms of net photosynthesis (Pn) in respect of H. At 25°C HS shows higher stomatal conductance (g s ) compared to H. Pn (net photosynthesis) and E (evapotranspiration) are inextricably linked through g s (Miyazawa et al 2006); g s responds to Ci concentration such that the ratio of ambient CO 2 (Ca) and Ci remains constant.…”

Between and within-site comparisons of structural and physiological characteristics and foliar nutrient content of 14 tree species at a wet, fertile site and a dry, infertile site in Panama

“…Chazdon and Kaufmann (1993) found that while two species of rain forest shrubs adapted similarly in terms of leaf structure (thicker leaves, higher leaf mass per area) under high light, their physiological response to higher light levels differed. Several genera such as Shorea, Entandrophragma, Syzygium, and Macaranga have exhibited different responses to light levels, thereby enabling these species to divide the available light and co-exist within the forest (Ashton and Berlyn, 1992;Ashton et al, 1995;Davies et al, 1998;Gamage et al, 2003;Hall et al, 2003).…”

“…Three principal environmental gradients -light, precipitation, soil nutrients -have been studied extensively in tropical forest ecosystems worldwide, elucidating how species interactions with various environmental conditions determine forest composition, diversity, structure, and succession (Ashton and Berlyn, 1992;Wright, 1992;Ashton et al, 1995;Gamage et al, 2003;Hall et al, 2003;Givnish et al, 2004;Ashton et al, 2005). Tree species adjust physiological traits, such as net photosynthetic capacity, transpiration and growth rates, and shoot:root ratios, in response to different light and soil moisture regimes (Bazzaz, 1979).…”