Oecologia (1989) 81 :528-533 Decologia Q Springer-Verlag 1989

Energy content, storage substances, and construction and maintenance costs of Mediterranean deciduous leaves

l 1 2 S. Diamantoglou , S. Rhizopoulou , and U. Kul1 I rnstitute of General Botany, University of Athens, Panepistimiopolis G R~15784 Athens, Greece 2 fliologisches instilut, Universitiit Stuttgart, 0-7000 Stuttgart 80, Federal Republic of Gcnnany

Summary. AI monthly intcrvals water conlent, crude fibre, struetion cost values for leaves of deciduous chaparral total and protein nitrogen, sugars, starch, total lipids, ash shrubs, Merino et al. (1982, 1984) found higher values for content and calorific tolal energy were measured through­ drought deciduous leaves than for evergreen leaves. Wil­ out the lifespan of the leaves of the dcciduous mediterra­ liams et al. (1987) confmncd these findings using their own nean shrubs Pistacia terebinthus L. and Cotinus coggygria method of calculation of the construction cost. Our earlier Scop. From these data the construction costs and mainte­ investigations of the seasonal trends of storage substances nance costs, as well as the construction costs of non-storage we re confined to evergrcen species (Diamantoglou and Kull compounds and energy expenditure values we re calculated. 1982, 1988; Diamantoglou et al. 1989). In this paper, we The latter values were also calculated for the evergreen report on the slorage compounds and the energy content stemmed shrub Ephedra distachya for reasons of compari­ of two deciduous shrubs, Pistacia terebilllhus and Co /inus son with an evergreen mediterranean species. The water coggygria. of the European mediterranean vegetation. Ac-­ status in the deciduous leaves is stable for a long time during cording to the methods of Williams et al. (1987) and Mcrino the drought period until the beginning of senescence in Au­ el al. (1984) we calculated the construction and mainte­ gust/September. In Cotinus an early and considcrable in­ nance costs, which arc compared with their data on chapar­ crease of storage compounds is found, whilst in Pistacia ral shrubs and with the values calculated from our results terebimhus the accumulation is more uniform until August. on the evergreen stemmed mediterranean shrub Ephedra The N-content is rather low compared with other deciduo us distachya (Diamantoglou et al. 1989). leaves, the calorific energy is in the lower range of tbe values reported for similar species. The construction costs of the Materials and metbods leaves of both deciduous species arc significantly lower than those calculated by Williams et al. (1987) for two drought Materials deciduous chaparral species but are in agreement with the Leaves of deciduous species Co/inus coggygria Scop. data re ported by other authors on deciduous leaves. Con­ ( = Rhus cotillus L.) and Pis/acia terebinrhus L. (both Ana­ trary to the findings of Williams et al. they are lower than cardiaceae) werc taken from the shrubs of about 1,5 m those of evergreen species; this is also true when the con­ height, growing on rather deep soil in openings of natural struction cost of the non-storage compounds alone is con­ macchia·like vegctation ncar Malakassa (40 km N of Ath­ sidered. The values found for Ephedra are simi lar 10 the ens) on a NE-exposed slope of the lower part of the Parnes values reported in the literature on evergreen leaves. The Mountain (about 380 m NN). Leaves from marked maintenance costs do not show a significant variation in branches were taken (around 1000 a.m.) at monthly inter­ the deciduous leaves. They are higher than those known vals starting in March when the leaves begin to sprout and for evergreen leaves but somewhat lower than the values later until the number of leaves on control shoots of similar calculated for deciduous chaparral leaves. shape had deereased by natural defoliation to about 25% of its initial val ue. The defoliation of the shrubs started Key words : Calorific energy - Storage compounds - Pista­ from late Augusl onwards. In September some of the leaves cia - Cotinus - Ephedra started to turn yellow and by October most of them were yellowish and senescent Climatic data of the harvesting pcriod during 1985 are In the Mediterranean type of vegetation, we find the differ­ shown in Fig. 1. The dry summer period lasted for about ent life fonns of evergrcen shrubs, considered to be drought 4 months. tolerators, and of deciduous s~ies , thought to be drought avoiders. It has been known that this deseription is too Methods simplified (Ehleringer and Mooney 1983; Mooney 1983) inasmuch as deciduous shrubs also show important physio­ Immediately after harvesting, one part of the leaves was logical properties similar to those of the evcrgreen specics put into plastic bags and di pped into boiling water for (Harley et al. 1987). Interestingly, upon calculating the con· 10 min. In the laboratory they we re then dried in a vcntila­ tion oven at 600 C. The other pa rt was frozen immediately Offprint requests to: U. Kull and stored at - 20 0 C ror the investigations. l29

mm rainfall combustion of the plant material in a muffle furnace for 1,5 h at 5000 C. Based on the values obtained. the calcula­ 70 tion of the energy equivalents was corrected and designated as the energy of ash-free substa nce (EAF-val ue). The construction cost was calculated (as g glucose/g dry matter) according to the method of Willaims et al. 50 (1987), using a value for growth efficiency Eo = 0.87 (Pcn­ ning de Vries et al. 1974, Penning de Vries 1975 ; McDermitt and Loomis 1981) and considering nitrale as the nitrogen 30 source. The maintenance cost (g gl ucosc/g dry matter x day) was estimated using the mnintenance coefficients of and the method described by Merino et al. (1984). Since these 10 authors gave a minimum and maximum value of the main­ tenance coefficients for proteins and for ions, the average values of these coefficient.s we re used to calculate an average days with temperature maxima mai ntenance cost of the leaf substances. higher than 35 0 C The construction cost of the storage compounds was calculated using the values: _...,.<=233~=::> 'C 1 g sugars equivalent to 1 g glucose 30 1 g sta rch equivalent to 1.173 g glucose 1 g lipid equivalent to 2,852 g glucose 20 (Larcher 1980; HolTmann J985). (A rather high content 10 of resins in Pis/acia may cause an error in the calcul:ttion of the construction cost of storage compounds; in Co/intiS (and Ephe(/ra) the error will be only small.) The difference 3 , 5 between the total const ruction cost and the construction cost of the storage substances may be considered as the Fig. I. Climatic dala during the period of investigation. Top : construclion COS I of the non-storage substances which monthly rainfall; bOllom: monthly mean temperatures mainly comprisc the constructive components of the tissue (secondary plant substances are disregarded, this is thought to be a major source of inaccuracy). A fraction of the con­ Soluble sugars were analy.a."

crude fibre total sugar 50 % dr y matter 7 % dry mott.r 40 6 )J 5 4 20 l N - content 2 mg/g dry motter 30

20 3 10 2

protein - N )J mg/g dry mQttI~ r to tal lipids 20 7 % dry matter 6 10 5 chtorop'hyl\ content 4 l mg/ g fresh weight 4---A-_-..I. 3 tJ ~'- '\ 2 , , ,, , ,. " 2 34 567 89 ' 0 345678910 month month Fig. 2. Crude fibre content, tOlal·N content, protein-N content and .'ig. 3. Total sugar content, starch content and total lipids content chlorophyll content of leaves of Pi$tacia urebinlhus and COlinus of leaves of Pisf(/cia Icrebinlliu$ and Co/inus coggygria coggygria 0 "" Pislacia; .:. '" COlinus (also Figs. 3 and 4) tent rises in spring and then starts to diminish during the From the data shown, the construction and mainte­ drought period. This effect is less distinct in Pislacia, per­ nance costs as well as the energy expenditure of the leaves haps because of a significant amount of resins in the lipid are calculated (Fig. 5). No complcte set of data is available fraction. Tn spring, starch is considerably accumulated in to allow for the calculation of these values according to the leaves of CO/iIllIS, but not of Pis/acia. In both species, the methods used in this paper rega rding shrubs or trees only the sugars sucrose, glucose and fructose (the lalter with evergreen leaves of the European Mediterranean vege­ in smaller amounts) are accumulated. The amounts of the tation. For comparison, therefore, tbe corresponding values m~osaccha r idcs are found to be highest in August in both of the leafless evergreen chlorophyllous stemmed shrub species. In Pistacia. the highest content of sucrose is also Ephedra distachya were calculated fro m the data published observed in August, but in Colinus it is observed in June. by Diamantoglou et al . (1989). They are also shown in The ash content of the leaves increases during their life­ Fig. 5, The construction costs of the deciduous leaves of time (Fig. 4). The total calorific energy (CTE) values both species arc very Similar; the values for Ephedra are (Fig. 4) remain rather constant in Pislacia leaves and de­ significantly higher. In COlinlls leaves the construction cost crease somewhat in Cotinus. The energy content of tbe main decreases with increasing leafage, while in the case of Pista­ storage products (ECS-value; Fig. 4) was estimated for cia leaves, it is relatively constant th roughout their livespan. Pistacia leaves to range from 1,6-3 kJ jg, for Cotinus leaves, The same is true for the evergreen twigs of Ephedra. Thc values from 0,9- 3,1 kJjg are found, In Pisracia, the storage construction costs of the non-storage substances behave substances are accumulating until August and start declin­ similarly but increase in the seneseing leaves. In Ephedra, ing when the symptoms of senescence are visible. In Cotill­ the construction cost of the non-storage substances is lower us, the accumulation is more pronounced during the leaf during the late growth period and higher from autumn to growth period and the highest value is found already in March. June. Less energy of storage substances and less total energy The average maintenance costs of the deciduous leaves of the organic substance (energy of the ash-free dry matter, show no significant variations. In Ephedra, maintenance EAF, Fig. 4) are at disposal to the decomposers in the eco­ costs decline throughout the late drought period as a result system by the defoliation of COlinus then of Pistacia. of the decrease of lipid and protein components (comp. 53 '

ash content construction cost 10 % dry matter 2 giucose/g

9 ,, 1.5 - ~ ... --.- ~ 8 , ..•. , ,/-- """ - / 6 construction cost non storage I 2 9 g1ucose/g 5 I:r _.If 4 1,5 ~-+-+- ... --+----+-+ ~ EGT 19 kJ/g dry matter 18 maintenance cost OJl2 9 glucose Ig. day 17 ~ /+-+-+ QO! EAF .. ' +- ...:..--:-.:./ ;)J kJ/g ash free dry matter

energy expenditure Q4 9 glucose/g -- ...... +-+-+ ECS kJ/g /A_. 0,3 • .------...... - 3 , 2 , , , K ~ - . -- . -:o 1 .,' 0,2 -.

345678910 3 4 5 I; 7 8 9 '(l 11 12 1 2 month month Fig. 4. Ash content , calorific total energy (EGT), energy content Fig. S. Construction costs (as g gl ucose/g dry matter), construction of the ash-free dry matter (EAF) and energy content of the storage costs of the non-storagc substances, maintenance costs (as g glll ­ substanccs (ECS) of leaves of Pis/ada terebinl/lllS and CQfinu$ cog­ cose/s dry matter x day) and encrgy expenditure (as g gl ucose/g gY8 r;Q dry matter) of tbe leavt'S of Pis/acia lerebinlllllS and COlinus cogg)l­ gria during tbei r lifespans and of green shoots of Ephedra disloch),o during one year, 0 '" Pistacia ; "' ... Cotlnus ; + = Ephedra

Diamanloglou cl al. 1989), The average maintenance costs of Pistacia /erebimhus (Mooney 1969). The crude fibre con­ in the deciduous leaves arc higher onl y by a small fraclion tent in our deciduous leaves shows val ues similar 10 those than in evergreen Ephedra twigs. found in leaves of diverse evergreen species. Also, the chlo­ The energy expenditure values calculated from the con­ rophyll content is in the same range as fo und for the ever­ struction coSts according to the method descri bed decline green species. Interestingly, the total-N and protein-N COIl ­ in the leaves of the deciduous shnlbs but remain rather tents also show similar values as in the evergreen species. constant in the Ephedra-twigs. Thc decline of the N-conlcnt in senescing leaves is probably due to an export of N-compounds; the fin al concentrati on in the dying leaves of 3-5 mg,lg dry matler is in the same Discussion range as found for evergreen leaves. The results of our inves ti gation of the tWO deciduous medi­ The accumulation of soluble sugars during the summer terranean shrubs may be compared with the data on ever­ drought period is more distinct in the deciduous species green shrubs, especiaU y Pis/acio /cl1IisC/Js, of the Greek than in the leaves of P. /emiscllS (Diamantoglou and Mele­ phrygana vegetation near Athens (s ummari zed in Diaman­ tiou-Christou 1979; Di amantoglou and Kul! 1982). A rise loglou and Kull 1982, 1988) and also the results reported of the osmotic pressure during the summer period in the on chnpanal plants ofCaJifornia (Merino el a!. 1984). leaves of all three Anacardi(lceae is by and large parallel The water content of the mature leaves of Pislacia tere­ to the total sugar content. Therefore, it is thought to be bimhus and Co t/nus is similar to that of the evergreen Pis/a­ an active increase due to d rought avoidance, as discussed cia lemisells at their specific natural stands, which ha ve by Kull and Breckl e (1972). different water-supplies. Under identical stress condi tions, The ash-content of the leaves in our deciduous species the transpiration rales of Pistacia lent/Jells are lower than is in the ra nge listed by Pi pp and Larchcr (1988) for leaves m of such shrubs in the Mediterranean climate. The values productively relatively long throughout the drought period. are higher than those measured in Lepl!chiniu (Merino et a!. This could be attained by a stable plant water status ca used 1984). The calorific lotal energy (EOl) - values are in ac­ by a good stomatal control during the onset of drought cordance with the data of Pipp and Latchet (1988) on RII­ at the natural stands; in contrast to the findings of Poole lanae. and Miller (1975) on Californian chaparral species. The The construction costs of the leaves of P. terebinthus data of Harley et al. (1987) on photosynthesis and water and COlinus are significantly lower than those calculated Status of the drought deciduous Cistus salvifolius leaves al­ by Williams et al. (1987) for the two drought deciduous low us to suggest a similar behavior of the leaves of p . chaparral species. The earlier publications of data on decid­ terebinlhu~' and CO linUJ . which on the basis of their anato­ uous 1e-1Ves, in most cases, originate from annuals and re­ my, are somewhat more sclerophyllous than those of CistUJ. port an average of about 1.3 (Hunt and Loomis 1979). The strategy of the accumulation of storage substances This is in agreement wi th our data on the funy ex.panded in the leaves of ColimlS and P. lerbillthus seems to be some­ leaves. The dccre.1.se with age of the CQnstruction costs of what different. In COIinus, there is an early and considerable dedduous leaves is much more distinct in the chaparral incrcase ofs!of!!ge compounds, whilst in P. lerebinthus the shrubs than in our species; its possible ca uses are discussed accumulation is continuous and morc uniform until August. by William s c\ al. (1987). The construction cost values ob­ This suggests a st abilization of the plant water status in tained for the chlorophyllous stemmed eve rgreen shrub COlillus by prolonged periods of stomata closure compared I£phedracorrespond with the costs for the evergreen Helero­ to P. /erebinlhus. mefes leaves found by Williams el a!. {l987) and are nea rl y As Harley ct al. (1987) pointed out, there is a conlilluum in the same range as those found fo r Pi/IUS laeda (Chung of response from sclerophyllous evcrgreen to drought decid­ and Barnes J977). uous shrubs. Based on their findings on Cis/lIS, from our The green tissues of Ephedra are somewhat more expen­ data on Pislacia rerebin/hllS and COtillllS, it may be con­ sive to construct than the deciduous leaves of P. rerebillthu.f cluded that these species show also intermediary character­ and COlillUS despite of a very similar protein content. This istics betwccn sderophyllous drought tolcrators and decidu­ is also true when the conSlfuction cost of the non-storage ous drought avoiders. compounds alone is considercd. Thc higher construction Long li ved assimilating tissues have to invest more ener­ cost fOllnd fo r the assimilating evergreen tissues agrees with gy illlhcir defense against herbivory. The protective mecha­ earlier findings. which arc discussed in detail by Chabot nisms vary in different species which may be a possible and Hicks (1982). However, we have our reservations, be­ explanation for the different metabolic costs. Hitherto, this cause no comparable: data arc available on evergreen true has not been taken into considcration in calculating con­ leaves of European Mediterranean species. Contrary to our struction costs. Ephedra syn thesizes ephedrine, which is effi­ findings, Merino et a!. (1984) reported that tbe leaves of cient al ready in low concentrations and therefore, not very the deciduous cbaparral species arc more expensive to grow expensive. Fresh leaves with low scleropbylly frequently that those of the evergreen J/eteromeles. found in the deciduous species of the mediterranean type The maintenance cost values obtained for /:.phedra arc vegetati ons are consumed by herbivores prefef"'d bly. The wen comparable to the values cale:ulated by Merino et al. leaves of Pistacia and COlinus show a rather high crude (1984) for the He t erom ele~' leaves. In contrast, the mainte­ fibre and a low protein-N content. Furthermo re, Anaear­ nance cost values found fo r the European decid uous spc<::ics diaceae arc well known for the production of substances arc lower than those found by Merino et al. for Ihe chapar­ acting as allergencs. Perhaps the hi gher construction COSL~ ral deciduous species. In Ephedra, they decrease somewhat of the deciduous Californian chaparral species, Dip/oeus during \.he late growth period due to the decline of lipid and Lepechinia (Merino et al. 1984; Williams et al. 1987) and protein contents. The maintenance costs of the decidu­ arc partly due to the production of higher amounts of more ous leaves are higher than those found for evergreen (issues, expensive secondary substances effective as protectives. In but the difference is nOI as pronounced as found by Merino concl usion, there seem to be different strategies of semi­ et al. (1984). The observed differences in maintenance costs drought-dcciduous shrub species in the Mediterranean type arc in agreement with the conclusion of Bloom el at (1985) of vegetation in relation to drought resistance and defense that the total maintenance costs may not vary greatly against herbivory. among tissues and species considering their different tife­ spans. AcknQwledgemenlJ. Thanks are duc to Mn . U. Friederich for valu­ As Schulze (1982) and Schulze and Chapin (1987) able eJ(perimcntat help, Mrs. Dip!. BioI. A. Herbig for diSCUSSions stated, there are differellt strategies of the different life and Mrs. B. Solis·Schreiur for corn.:ction of the English. Part of forms and soecies, wnich are correlated with variations in the research was supported by the DFG (SFB 2l0). the effi ciency of metabolic processes, ion-uptake, N-gain, -storage and -utilization and different adaptibili ties of these Rderences processes to stress factors. Therefore, it could be expected that the three species investigated would havedifTerent ener­ Bligh EG. Dyer WJ (1959) A rapid method or total li pid eJ(tracuoo gy expenditure val ues which decrease during the lifespan and purification. Canad J Biochem Pbysiol 37:911-917 of the deciduous leaves and which remain obviously stable Bloom AJ, Cbapin III FS, Mooney HA (1985) Resource limitation in plants - an economic IInatogy. Ann Rev Ecol SYSI in the Ephedra shoots (w hich have an average lifespan of 16 :363-392 about 2- 3 years) during tbe period of investigation. Chabot BF, Hicks 01 (t982) The ecotogy of leaf tife span. Ann In P. lellliscus and COlinlls, lcavcs arc produced in early Rev Ecol SySt 13: 229- 259 spring and retained until Septem ber. Because the lifespan Chung HH , Barnes RL (1977) PhOlosynthate allocation in PmUj of the leaves should be related to a balance between the raeda. I Sub$lrate requirements for synthesis of shoot biomass. construction costs and the benefit s, the leaves must live CanJ For Res7 :106-I LI 53l

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