Reproductive effort of some annual and perennial plant species: Impact of succession sequence,habitat conditions and plant size

The reproductive effort of some annual and perennial plant species was investigated with respect to successions sequence,habitat conditions and plant size,hi the psammosere succession (dune succession),the reproductive effort (re) of cressa cretica znaatriplex griffithii was significantly greater in the early stage compared to that in late succession. likewise,in relation to lithosere succession,sporobolus arabicus,pluchea lanceolata and vernonia cenerescens all showed high reproductive effort in early part of succession compared to that of late succession. the annuals (s. arabicus and p. lancolata) exhibited greater reproductive effort compared to the perennial species vernonia cinerescens. examination of the impact of site differences on reproductive effort showed that four grasses including setaria intermedia,chloris barbata,cenchrus biflorus,and eragrostis pilosa were found to have significantly (p<0.05) greater reproductive effort in site 1 (near cultivated field),compared to site 2 (a vacant lot),which had low nutrient level compared to site 1. the reproductive effort of sonchus asper (a composite) did not exhibit significant difference between sites. the investigation of relationships between plant size (volume) and reproductive effort of solarium forskalii,senna holosericea and heliotropium ophioglossum showed positive correlations between plant size and reproductive effort. solanum forskalii and senna holosericea,in particular,exhibited a close association in this respect. it is concluded that: 1) re is greater in early compared to late succession,2) re changes with the habitat and 3) there seems to be a direct relationship between re and plant size.