Growth, photosynthesis and nutrient content of seedlings and mature plants of 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 types 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 centrifugally from the patch edge, (3) mature shoots with well-developed rhizomes growing in the patch proper, and (4) isolated mature shoots not attached to a seed coat and with rhizomes, but growing singly or with only a few (<5) shoots attached to the same rhizome. The data do not allow a final conclusion on 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 Pmax (4.92 mg O2 g-1 DW h-1) of the four shoot types, followed by runner shoots (2.58% N, 0.13% P; RGR 0.036 g DW g-1 DW d-1, Pmax 3.87 mg O2 g-1 DW h-1). Patch plants and isolated plants had N concentrations of 2.302.01% and P concentrations of 0.101-0.099%, with RGRs of 0.027-0.025 g DW g-1 DW d1. The low nutrient 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, possibly indicating translocation from runner to patch shoots. The data emphasize the importance of establishment and development of new patches from seeds, but also the importance of clonal integration once a patch has become established.