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DEVELOPMENT OF DIFFERENCES IN LEAF SHAPE IN BEGONIA DREGEI (BEGONIACEAE)
Author(s) -
McLellan Tracy
Publication year - 1990
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1990.tb13562.x
Subject(s) - biology , primordium , heterochrony , apex (geometry) , botany , allometry , begonia , phyllotaxis , leaf size , ontogeny , evolutionary biology , shoot , paleontology , meristem , biochemistry , genetics , gene
There is a wide range of variation among individuals in the degree of incision of leaf margins in the African Begonia dregei. The development of adult leaves was examined in six varieties of B. dregei. There are several types of differences in development that correlate with the shapes of mature leaves. The shoot apex is larger and the leaf primordia are broader soon after initiation in a variety with entire margins than in those with more incised leaves. One variety differs from the others in the temporal pattern of initiation of the lobes, corresponding to differences in the relative sizes of the lobes of the mature leaves. The differences among varieties in the extent of incision of the margin are apparent during the first plastochron, before the primordia are 300 μ m in length. All are more deeply incised early than when mature. Growth rates of the different parts of the leaves change with respect to each other during development in the more deeply incised varieties. The leaves of the three least incised varieties reach similar mature shapes by two different developmental pathways. Differences in the relative timing of developmental processes provide a description of some of the evolutionary changes responsible for differences in shape. However, simple heterochrony does not describe all aspects of the diversification of leaf shape in this species.