Growth phenology of Pleurophycus gardneri (Phaeophyceae, Laminariales), a deciduous kelp of the northeast Pacific

Abstract

Growth phenology of the monotypic northeast Pacific kelp Pleurophycus gardneri was assessed between 1982 and 1984. The study gives evidence that Pleurophycus is a deciduous perennial. Pleurophycus shows complete and synchronous defoliation during a short period of time in late fall and commences new blade growth after about 2 weeks of quiescence. Pleurophycus sheds the lamina along an abscission zone at the transition between stipe and blade. The abscission zone is macroscopically evident through a change in color and a slight indentation in senescent plants. After separation, outer cortical cells constitute a protective layer which increases in thickness as new blade outgrowth progresses. Temperature of 14 to 15 °C is assumed to be a triggering factor for the induction of blade senescence. Warm water intrusion, associated with E1 Ninõ, induced premature blade senescence and blade abscission in 1983. Growth of the new blade is completely inhibited in darkness. The induction of new outgrowth is not mediated through a photoperiodic effect and showed no day-length saturation.

Rapid phlorotannin induction and relaxation in five Washington kelps

“…P. gardneri is different from the other subtidal species in that the blade is shed in late fall in the San Juan Islands and regenerated from the intercalary meristem shortly thereafter (Germann 1986). P. gardneri blades gradually decrease in dry weight, man.nito1, and laminarin content prior to abscission (Germann 1986), and stipe and holdfast tissue contain the majority of nitrogen products (Germann et al 1987). Thus the annual blade tissue may be relatively less important than the perennial stipe and holdfast.…”

“…Pleurophycus yardnen Setchell & Saunders is patchily distributed in the San Juan Islands, from the low intertidal to upper subtidal zones, and primarily in areas of high current. The blade of P. gardneri is deciduous, shed entirely each fall and regenerated a few weeks later (Germann 1986). Laminaria complanata is found only in Washington and British Columbia (Canada).…”

Dynamics of carbon allocation in a deep-water population of the deciduous kelp Pleurophycus gardneri (Laminariales)

“…The P/R ratio was slightly higher in this deep-water population than in the intertidal one studied by Germann (1989); however, it was not higher than in other kelps such as Macrocystis pyrifera (Zimmerman & Kremer 1986, Table 4). Size and morphology of these deep-water plants were also different from those studied by Germann (1986). Average stipe lengths of those deep adult plants chosen for this study were generally twice as long (40 to 50 cm) as the average stipe length of intertidal plants (20 cm) studied by Germann (1986), but blade area was similar to intertidal plants.…”

“…The top of the stipe was flat and broad near the blade junction, then narrowed and became elliptical with each constriction (with slight turning and rounding between constrictions), and was round toward the holdfast. Although stipe growth was not quantitatively measured during the bladeless period, cell expansion or growth was observed just below the meristem, as indicated by several centimeters of new, lightly pigmented tissue.Growth rings in the basal portion of the stipe of deepwater Pleurophycus gardneri were unexpected because they are absent in intertidal plants (Germann 1986). Validation of growth ring chronology allowed assessment of maximum observed age of 5 yr in this deep-water population (Dominik 2004).…”

“…Without the reserves located in the perennial stipe and holdfast the plant should die before blade initiation in spring. The photosynthetic efficiency of deep-water plants was twice that of intertidal plants, which have very low compensation depths (Germann 1986). This study also demonstrated that models, which incorporate photosynthetic production, should account for canopy geometry and orientation relative to the submarine light field and possibly the quality of in addition to the quantity of in situ irradiance.…”