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A cluster of sporangia on the lower surface of a fertile fern leaf.
A clump of reproductive bodies or spores in lower plants.



in plants, a dense cluster of reproductive organs, for example, sporangia in ferns, zoosporangia in the brown alga Laminaria, and oogonia in the brown alga Dictyota.

References in periodicals archive ?
In addition to the dramatic decrease in sorus area following the storm, individual Macrocystis lost on average 60% of their fronds.
For both Macrocystis and Pterygophora there was a significant positive relationship between the total spore release for a sample period (as estimated by total decrease in sorus area or in sporangium density summed over all individuals for Macrocystis and Pterygophora, respectively) and the percentage of individuals that showed net spore release during the same sample period, as indicated by a decrease in sorus area or sporanglum density ([F.
For a given sample period, total spore release in Macrocystis (total decrease in sorus area summed over all plants sampled) was positively correlated to the density of female gametophytes that settled in the study area; however, it only explained a relatively small amount of variation ([F.
Synchronized reproduction in Pterygophora is most likely triggered by photoperiod, which is known to activate growth in Pterygophora (Luning 1993) and sorus formation in other perennial kelps (Luning 1988, tom Diek 1991).
Periodic control in sorus formation in the brown alga Laminaria saccharina.
Circannual growth rhythm and photoperiodic sorus induction in the kelp Laminaria setchellii (Phaeophyta).
This seasonal pattern of spore allocation in Macrocystis was not observed in 1992 when sorus area per frond was relatively low and variable throughout the year.
Compared to reproductive allocation, seasonal variation in spore standing stock (estimated as sorus area per plant) in Macrocystis was less consistent among years.
In comparison to Naples Reef plants, however, Shallow Goleta Bay plants were generally larger (and presumably older) with substantially more sorus area, both per plant and per sporophyll.
Finally, spore C/N was unrelated to sorus area in both species.
Sorus area per frond and sorus area per plant in Macrocystis remained negatively correlated with temperature, even when analyses were confined to data collected during the cool months of November through April (Table 4).
The significant relationship between germination success and spore C/N or sorus area per frond (Table 4) appeared to be entirely due to the low values of germination observed during April and May 1993.