Growth, photosynthesis and nutrient content of seedlings and mature plantsof Cymodocea nodosa - the importance of clonal integration

This paper presents data on nutrient (N and P) content, chlorophyll content , dark respiration, photosynthetic rate and relative growth rate of four ty pes of shoots of Cymodocea nodosa in Alfacs Bay, NE Spain: (1) seedlings, i .e. young shoots still attached to the seed coat, (2) shoots in runners, i. e. shoots growing in fast-growing horizontal rhizomes extending centrifugal ly from the patch edge, (3) mature shoots with well-developed rhizomes grow ing in the patch proper, and (4) isolated mature shoots not attached to a s eed coat and with rhizomes, but growing singly or with only a few (<5) shoo ts attached to the same rhizome. The data do not allow a final conclusion o n source/sink relationships in Cymodocea patches to be drawn, but seedlings had the highest nutrient content (2.75% N, 0.20% P) as well as the highest RGR (0.047 g DW g(-1) DW d(-1)) and P-max (4.92 mg O-2 g(-1) DW h(-1)) of the four shoot types, followed by runner shoots (2.58% N, 0.13% P; RGR 0.03 6 g DW g(-1) DW d(-1), P-max 3.87 mg O-2 g(-1) DW h(-1)). Patch plants and isolated plants had N concentrations of 2.30-2.01% and P concentrations of 0.101-0.099%, with RGRs of 0.027-0.025 g DW g(-1) DW d(-1). The low nutrien t concentrations in patch shoots indicated they experienced severe nutrient limitation. In addition, runner shoots used a lower proportion (about 30% less) of photosynthetically acquired carbon for growth than patch shoots, p ossibly indicating translocation from runner to patch shoots. The data emph asize the importance of establishment and development of new patches from s eeds, but also the importance of clonal integration once a patch has become established. (C) 2000 Elsevier Science B.V. All rights reserved.