Source-sink characteristics of carbon transport in Chara hispida

Abstract

Rates of uptake of '^C-labelled inorganic carbon wet-e tncasut-cd for whole Chara hispida plants, detached parts of the shoot and isolated (^split-chamber technique) apices, latet-al bt-anchlets atid rhizoid-node cotnplexes.The rates of inot-ganic carbon uptake by the rhizoid node cotnplex exptessed per gratn ftesh weight whole plant were tht-ee to four ot-dcrs of tnagnitude less than the uptake for the whole plant. Up to 70% of the carbon taken up by the rhizoid node cotnplex was translocated to the shoot. After 12 h exposute to '"^C-labellcd inot-ganic carbon the concentration of '"^C was greater in apices than in uppertnost or ccnttal internodal cells and in all latetal branchlets, t-cgat-dless of whether label was supplied to the whole plant or isolated thizoid-nodc complexes, Measutement of inot-ganic carbon uptake by detached internodal cells and detached and isolated apices and lateral btanchlcts showed that latct-al branchlets had the gt-catest rates of inorganic carbon uptake, Duting 12 h exposure to '•*C, isolated latet-al branchlets tt-anslocated to the attached shoot 55% of the labelled carbon taken up; for isolated apices this value was only 13%, It is concluded that it is highly unlikely that the rhizoid of Chara hispida could acquiie a significant fractioti of the whole plant lequitetnent for inotganic carbon and that apices ate sink regions for photosynthate while lateral btanchlets ate source tegions.

Phosphate uptake by the component parts ofChara hispida

“…Culture conditions were as described previously (Andrews et al, 1984a) except that the growth temperature was 12_+ I°C. The lowest lateral branchlets of the cuttings were trimmed off and the remaining node was completely covered with substrate.…”

“…Two or three determinations were carried out at each phosphate concentration used. In each case the rhizoid-node complexes of six plants were isolated from their attached shoots using the split chamber technique described previously (Andrews et al, 1984a). The pH of the culture media in the compartments containing the rhizoids and shoots were 6'8_+ 0.2 and 8-2+0.1 respectively: these pH values correspond approximately to those existing in the interstitial water of the sediment and the open water in the field site.…”

“…Photosynthetic pigment content and rates of 14C uptake and O2 evolution for the component parts of C. hispida indicate that, lateral branchlets are its major site of photosynthesis and that, even when a substantial rhizoid system is present, C uptake by the rhizoids is negligible (Andrews, et al, 1984a;Andrews et al, 1984b;Andrews et al, 1984c). Tracer studies using 14C indicate that over 50% of C taken up by the lateral branchlets is translocated to the rest of the shoot in particular the apical meristems, while apices retain approximately 90% of the carbon they take up (Andrews et al, 1984a).…”

“…Tracer studies using 14C indicate that over 50% of C taken up by the lateral branchlets is translocated to the rest of the shoot in particular the apical meristems, while apices retain approximately 90% of the carbon they take up (Andrews et al, 1984a).…”

AFestschriftin honour of Professor John A. Raven

“…One of us was fortunate enough to have had John as a lecturer at undergraduate level, as a Ph.D. supervisor, and then to have worked with him over the following 25 years building on some of his earlier work (e.g. Andrews et al 1984Andrews et al , 1999Andrews et al , 2005Andrews et al , 2009aRaven et al 2004Raven et al , 2005a. We highlight two areas of John's current research -firstly, 'Interactions among resources in the growth of phytoplankton', and secondly, 'The potential for photosynthesis on other planets'.…”