Leaf Longevity, Construction, and Maintenance Costs of Three Mangrove Species Under Field Conditions

Abstract

This study assessed the effect of leaf age on construction cost (CC) in the mangrove species Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle growing in their natural habitat. Leaf osmolality values were speciesspecific, the highest in A. germinans (1 693 mmol kg -1 ) and the lowest in L. racemosa (1 270 mmol kg -1 ). In the three species, contents of chlorophyll (a+b) (Chl a+b ) and nitrogen (N) per unit of leaf area were maximal in adult leaves and tended to decline with age. Leaf mass to leaf area ratio (LMA) and ash content increased during leaf ageing. Similarly, as leaves aged, a significant increase in leaf construction cost per leaf area (CC a ) was observed, while per leaf mass (CC m ) it remained almost constant, suggesting a sustained production of leaf compounds as leaves became older. CC was positively correlated with LMA and heat of combustion (Hc) per leaf area, suggesting differences among species in the quantity and composition of expensive compounds. Leaf half lifetime (t 0.5 ) showed contrasting values in the three mangrove species (60, 111, and 160 d in L. racemosa, R. mangle, and A. germinans, respectively). Overall, L. racemosa was the species with less expensive leaves to construct while leaves of A. germinans and R. mangle had the highest CC m and CC a , respectively. Leaf longevity was positively correlated with the ratio between CC and maximum photosynthetic rate (P max ), clearly showing the existence of a balance between leaf costs and benefits.

Photosynthetic performance of mangroves Rhizophora mangle and Laguncularia racemosa under field conditions

“…In contrast, responses of mangrove to salinity reflect alterations in photosynthesis, photosynthetic pigment content, trasnpiration rate, and enzyme activities. Generally, these negative effects also associated with other environmental factors, e.g., high light levels (TAKEMURA et al, 2000;KRAUSS and ALLEN, 2003).…”

“…However, other studies show that L racemosa is more tolerant to the negative effects of salinity (SOBRADO, 2004). Evidence for less salt sensitivity in mangrove species includes biochemical adaptations by wich mangroves counter the high osmolarity of salt, like accumulation of compatible solutes or enhanced gland secretion (TAKEMURA et al, 2000;KRAUSS and ALLEN, 2003;SOBRADO, 2004). In contrast, responses of mangrove to salinity reflect alterations in photosynthesis, photosynthetic pigment content, trasnpiration rate, and enzyme activities.…”

“…It is known that integrity of membranes, activity of several enzymes, nutrient acquisition, photosynthetic pigment content, gas exchange and photosynthetic apparatus function are affected by high NaCl concentrations (ZHU, 2001). In halophytes, some studies have showed that salinity inhibits photosystem 2 (PS2) activity, while others indicate the opposite (TAKEMURA et al, 2000;LU et al, 2002;QIU-FANG et al, 2005). Avicennia corniculatum and Bruguiera gymnorrhiza showed a decrease in the photosynthesis, whereas A. marina was not affected by the salinity (TAKEMURA et al, 2000).…”

“…In halophytes, some studies have showed that salinity inhibits photosystem 2 (PS2) activity, while others indicate the opposite (TAKEMURA et al, 2000;LU et al, 2002;QIU-FANG et al, 2005). Avicennia corniculatum and Bruguiera gymnorrhiza showed a decrease in the photosynthesis, whereas A. marina was not affected by the salinity (TAKEMURA et al, 2000). Other studies showed that salt stress by itself has little effect on the PS2 photochemical efficiency and on photosynthetic pigment content under relatively low light levels.…”

Crown architecture and leaf habit are associated with intrinsically different light-harvesting efficiencies inQuercusseedlings from contrasting environments

“…Seedlings of Mediterranean oaks can avoid high light stress due to the exposure to high irradiance by the protection of a large fraction of their foliar area, which is not displayed [46]. The low light-harvesting efficiency can be favourable considering a long-term carbon balance of the plant [42]. While all plants exhibit a relatively high capacity for physiological protection against excessive irradiance [26], only those from xeric sites exhibit architectural and morphological features that prevent them from surpassing the physiological limits of tolerance [43].…”