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leaf cuticular alkanes of cultivated Polyscias
BiochemicalSystematicsand Ecology,Vol. 14, No. 6, pp. 583-584, 1986. Printed in Great Britain.
0305-1978/86 $3.00+0.00 ¢) 1986 Pergamon Journals Ltd.
Leaf Cuticular Alkanes of Cultivated Polyscias TIMOTHY K. BROSCHAT and MICHAEL BOGAN University of Florida, Ft. Lauderdale Research and Education Center, 3205 S.W. College Ave., Ft. Lauderdale, FL 33314, U.S.A.
Key Word Index--Polyscias; Araliaceae; n-alkanes; chemotaxonomy. Abstract--Leaf cuticular alkane analysis of 34 cultivars of Polyscias generally supported morphological classifications of this genus, but variability within groups such as R crispatum suggested that alkane data by itself is insufficient for classification of the various cultivars into species. Alkanes with 27-33 carbon atoms were present in most species, with C3~ predominating.
Introduction in classification of species in other genera [5, 6] Aralias of the genus Polyscias have long been and is used in this study of aralia taxonomy. cultivated in the tropics as ornamental plants and in recent years have become popular tropical foliage plants for interiors. Taxonomy of Results and Discussion the group is complicated by the extreme Leaf wax alkane compositions were quite similar tendency for mutation among asexually propa- for the species of Polyscias examined (Table 1). gated plants, resulting in numerous cultivars in Alkanes C~9-C= accounted for at least 92% of each of the 6-8 cultivated species. In addition to the total alkanes present in all cultivars, with C31 problems with mutations, seedling variability is being the predominant compound in each case. great and these species are also known to With the exception of one cultivar each, none of hybridize freely. Plants are given a multitude of the P. crispaturn (Bull.) Merr., P. guilfoylei (Bull.) common names by horticulturists who grow L. H. Bailey, or P. filicifolia (C. Moore) L. H. Bailey them, but since the only existing classifications contained measurable amounts of either C27 or of Polyscias are based on leaf morphology [1-3], C= and could be easily separated from P. pinnata an extremely variable character in itself, the J. R. and G. Forst, P. scutellaria (Burm.) Fosberg boundaries between species remain unclear. and P. fruticosa (L.) Harms on that basis alone. The most current classification of cultivated P. frut~bosa differs from P. scutellaria and P. Polyscias [4] is based on leaf morphology and pinnata in that P. fruticosa has greater amounts known parentage of mutations, but it leaves of C32 and C~ and less Czl than the other two many questions about species boundaries species. Morphologically, P. scutellaria and P. unanswered. pinnata are quite similar, having orbicular leaves Although floral morphology is often used in or leaflets, but leaves of P. fruticosa are deeply classification of flowering plants, florets of incised and usually 2 or 3 times pinnate. P. Polyscias, which are tiny (1 mm in diameter), scutellaria and P. pinnata have been treated as appear indistinguishable under microscopic conspecifics by some authors, but differ in that examination. Inflorescence morphology is P. scutellaria leaves are almost invariably simple extremely variable within a species or even a and often cupped, while P. pinnata leaves are cultivar, making that a poor taxonomic character never cupped and have from 3 to 7 leaflets. also. For these reasons, biochemical methods P. crispatum and P. guiffoylei differ considerwere tested for possible use in classifying this ably in leaf shape, but have rather similar leaf variable, but economically important group of alkane compositions. In general P. crispaturn plants. Leaf alkane composition has been used has slightly more Czl and slightly less C~ than P. guiifoyle~ P. filicifolia, whose leaf morphology (Received 21 November 1985) differs somewhat from that of P. crispatum and 583
584
TIMOTHY K. BROSCHATAND MICHAEL BOGAN
TABLE 1. ALKANE COMPOSITIONOF POLYSClAS EXPRESSEDAS A PERCENTAGEOF TOTAL ALKANE CONTENT Species
C~7
C~
C~g
C3o
C3~
C~:,
C,
P. pinnata P. scutellaria P. crispatum P. fruticosa P. guilfoylei P. filicifolia P. grandifolia P. obtusa
4.5* 3.8 0.1 3.2 0.1 0.8 0.1 0.1
3.4 2.2 "< 0.1 2.6 <: 0.1 1.0 < 0.1 < 0.1
7.5 8.6 2.1 8.5 4.1 4.9 3.6 7~2
10.3 4.6 1.1 6.9 2.6 4.7 4.3 4.2
70.5 65.3 86.5 53.5 80.3 69.3 68.3 78.8
3.2 4.3 4.3 5.6 3.9 5.2 5.4 3.5
7.1 10.7 5.8 12.8 9.0 13.8 18.2 6.3
< < < <
*Values represent means for all cultivars and replicates included in each species according to Burch and Broschat [41.
R guilfoylei, had even greater quantities of C33 and less C31 than the other two species. One cultivar tentatively identified as belonging to R grandifolia Volkens was virtually identical to R filicifolia with respect to alkanes C27-Cz2, but had somewhat higher C~ levels than the latter species. This data neither confirms nor refutes the conspecificity of R grandifolia and R filicifolia. Certainly the two species are similar both morphologically and biochemically. The validity of the R crispatum group cannot be ascertained from the leaf alkane data alone. Although common in cultivation, aralias in this group have been ignored by most taxonomists. Leaf alkane composition varies widely within this group suggesting that perhaps it is an artificial grouping. However, cultivars with identical leaf morphology, but differing solely in the presence or absence of leaf variegation had quite different alkane compositions. Discriminant functions analysis [7] indicated the classification of aralia cultivars based on leaf cuticle alkane composition was equivalent to that based on morphological and mutation information. Results (not shown) indicate that 75% of the cultivars whose species identity was known were correctly classified using leaf alkane data. Although leaf alkane data generally supported morphological classifications, alkane data cannot be used as a sole data source for classifying aralia cultivars.
Experimental Two g of healthy, newly matured leaves were collected from each of the 34 cultivars of Polyscias spp. growing under identical environmental conditions. Five fresh replicate leaf samples of each cultivar were extracted in 100 ml CHCI 3 for 30 s with continuous agitation. Extracts were evaporated to dryness and hydrocarbons redissolved in 0.1 ml iso-octane. Hydrocarbon extract (40 p.I) was chromatographed on silica TLC in iso-octane and the alkane band removed from the plate. Alkanes were washed from the silica in iso-octane, evaporated to dryness, and taken up in 15 p.I of iso-octane just prior to GLC injection. Alkane samples were separated on a Micro-Tek 222 GLC with an FID and a 30 m glass capillary column coated with SE 54. Column temperature was programmed from 225 to 320° at 7 ° min 1 using an initial hold at 225 ° for 4 min and a final hold of 2 min. Alkanes were identified by retention time with respect to reference samples run under identical conditions and by their IR spectra.
Acknowledgement--This paper
is Florida Agriculture Experiment Stations Journal Series No. 6792. The authors wish to thank S. Boshell and R. Schill for their assistance in analysis of leaf samples.
References 1. Philipson, W. R. (1978) Blumea 24, 169. 2. Stone, B. C. (1965) Micronesica 2, 51. 3. Liberty Hyde Bailey Hortorium Staff (1976) Hortus Third. MacMillan, New York. 4. Burch, D. G. and Broschat, T. K. (1983) Proc. Fla. St. Hort. Soc. 96, 161. 5. Scora, R. W., Berthold, O. B. and Hopfinger, J. A. (1975) Biochem. Syst. Ecol. 3, 215. 6. Sorenson, P. D., Totten, C. E. and Piatak, D. M. (1978) Biochem. Syst. Ecol. 6, 109. 7. Sneath, P. H. A. and Sokal, R. R. (1973) Numerical Taxonomy. W. H. Freeman, San Francisco.
0305-1978/86 $3.00+0.00 ¢) 1986 Pergamon Journals Ltd.
Leaf Cuticular Alkanes of Cultivated Polyscias TIMOTHY K. BROSCHAT and MICHAEL BOGAN University of Florida, Ft. Lauderdale Research and Education Center, 3205 S.W. College Ave., Ft. Lauderdale, FL 33314, U.S.A.
Key Word Index--Polyscias; Araliaceae; n-alkanes; chemotaxonomy. Abstract--Leaf cuticular alkane analysis of 34 cultivars of Polyscias generally supported morphological classifications of this genus, but variability within groups such as R crispatum suggested that alkane data by itself is insufficient for classification of the various cultivars into species. Alkanes with 27-33 carbon atoms were present in most species, with C3~ predominating.
Introduction in classification of species in other genera [5, 6] Aralias of the genus Polyscias have long been and is used in this study of aralia taxonomy. cultivated in the tropics as ornamental plants and in recent years have become popular tropical foliage plants for interiors. Taxonomy of Results and Discussion the group is complicated by the extreme Leaf wax alkane compositions were quite similar tendency for mutation among asexually propa- for the species of Polyscias examined (Table 1). gated plants, resulting in numerous cultivars in Alkanes C~9-C= accounted for at least 92% of each of the 6-8 cultivated species. In addition to the total alkanes present in all cultivars, with C31 problems with mutations, seedling variability is being the predominant compound in each case. great and these species are also known to With the exception of one cultivar each, none of hybridize freely. Plants are given a multitude of the P. crispaturn (Bull.) Merr., P. guilfoylei (Bull.) common names by horticulturists who grow L. H. Bailey, or P. filicifolia (C. Moore) L. H. Bailey them, but since the only existing classifications contained measurable amounts of either C27 or of Polyscias are based on leaf morphology [1-3], C= and could be easily separated from P. pinnata an extremely variable character in itself, the J. R. and G. Forst, P. scutellaria (Burm.) Fosberg boundaries between species remain unclear. and P. fruticosa (L.) Harms on that basis alone. The most current classification of cultivated P. frut~bosa differs from P. scutellaria and P. Polyscias [4] is based on leaf morphology and pinnata in that P. fruticosa has greater amounts known parentage of mutations, but it leaves of C32 and C~ and less Czl than the other two many questions about species boundaries species. Morphologically, P. scutellaria and P. unanswered. pinnata are quite similar, having orbicular leaves Although floral morphology is often used in or leaflets, but leaves of P. fruticosa are deeply classification of flowering plants, florets of incised and usually 2 or 3 times pinnate. P. Polyscias, which are tiny (1 mm in diameter), scutellaria and P. pinnata have been treated as appear indistinguishable under microscopic conspecifics by some authors, but differ in that examination. Inflorescence morphology is P. scutellaria leaves are almost invariably simple extremely variable within a species or even a and often cupped, while P. pinnata leaves are cultivar, making that a poor taxonomic character never cupped and have from 3 to 7 leaflets. also. For these reasons, biochemical methods P. crispatum and P. guiffoylei differ considerwere tested for possible use in classifying this ably in leaf shape, but have rather similar leaf variable, but economically important group of alkane compositions. In general P. crispaturn plants. Leaf alkane composition has been used has slightly more Czl and slightly less C~ than P. guiifoyle~ P. filicifolia, whose leaf morphology (Received 21 November 1985) differs somewhat from that of P. crispatum and 583
584
TIMOTHY K. BROSCHATAND MICHAEL BOGAN
TABLE 1. ALKANE COMPOSITIONOF POLYSClAS EXPRESSEDAS A PERCENTAGEOF TOTAL ALKANE CONTENT Species
C~7
C~
C~g
C3o
C3~
C~:,
C,
P. pinnata P. scutellaria P. crispatum P. fruticosa P. guilfoylei P. filicifolia P. grandifolia P. obtusa
4.5* 3.8 0.1 3.2 0.1 0.8 0.1 0.1
3.4 2.2 "< 0.1 2.6 <: 0.1 1.0 < 0.1 < 0.1
7.5 8.6 2.1 8.5 4.1 4.9 3.6 7~2
10.3 4.6 1.1 6.9 2.6 4.7 4.3 4.2
70.5 65.3 86.5 53.5 80.3 69.3 68.3 78.8
3.2 4.3 4.3 5.6 3.9 5.2 5.4 3.5
7.1 10.7 5.8 12.8 9.0 13.8 18.2 6.3
< < < <
*Values represent means for all cultivars and replicates included in each species according to Burch and Broschat [41.
R guilfoylei, had even greater quantities of C33 and less C31 than the other two species. One cultivar tentatively identified as belonging to R grandifolia Volkens was virtually identical to R filicifolia with respect to alkanes C27-Cz2, but had somewhat higher C~ levels than the latter species. This data neither confirms nor refutes the conspecificity of R grandifolia and R filicifolia. Certainly the two species are similar both morphologically and biochemically. The validity of the R crispatum group cannot be ascertained from the leaf alkane data alone. Although common in cultivation, aralias in this group have been ignored by most taxonomists. Leaf alkane composition varies widely within this group suggesting that perhaps it is an artificial grouping. However, cultivars with identical leaf morphology, but differing solely in the presence or absence of leaf variegation had quite different alkane compositions. Discriminant functions analysis [7] indicated the classification of aralia cultivars based on leaf cuticle alkane composition was equivalent to that based on morphological and mutation information. Results (not shown) indicate that 75% of the cultivars whose species identity was known were correctly classified using leaf alkane data. Although leaf alkane data generally supported morphological classifications, alkane data cannot be used as a sole data source for classifying aralia cultivars.
Experimental Two g of healthy, newly matured leaves were collected from each of the 34 cultivars of Polyscias spp. growing under identical environmental conditions. Five fresh replicate leaf samples of each cultivar were extracted in 100 ml CHCI 3 for 30 s with continuous agitation. Extracts were evaporated to dryness and hydrocarbons redissolved in 0.1 ml iso-octane. Hydrocarbon extract (40 p.I) was chromatographed on silica TLC in iso-octane and the alkane band removed from the plate. Alkanes were washed from the silica in iso-octane, evaporated to dryness, and taken up in 15 p.I of iso-octane just prior to GLC injection. Alkane samples were separated on a Micro-Tek 222 GLC with an FID and a 30 m glass capillary column coated with SE 54. Column temperature was programmed from 225 to 320° at 7 ° min 1 using an initial hold at 225 ° for 4 min and a final hold of 2 min. Alkanes were identified by retention time with respect to reference samples run under identical conditions and by their IR spectra.
Acknowledgement--This paper
is Florida Agriculture Experiment Stations Journal Series No. 6792. The authors wish to thank S. Boshell and R. Schill for their assistance in analysis of leaf samples.
References 1. Philipson, W. R. (1978) Blumea 24, 169. 2. Stone, B. C. (1965) Micronesica 2, 51. 3. Liberty Hyde Bailey Hortorium Staff (1976) Hortus Third. MacMillan, New York. 4. Burch, D. G. and Broschat, T. K. (1983) Proc. Fla. St. Hort. Soc. 96, 161. 5. Scora, R. W., Berthold, O. B. and Hopfinger, J. A. (1975) Biochem. Syst. Ecol. 3, 215. 6. Sorenson, P. D., Totten, C. E. and Piatak, D. M. (1978) Biochem. Syst. Ecol. 6, 109. 7. Sneath, P. H. A. and Sokal, R. R. (1973) Numerical Taxonomy. W. H. Freeman, San Francisco.