Redroot pigweed (Amaranthus retroflexus L.) and slender amaranth (Amaranthus viridis L.) are considered emerging problematic weeds in summer crops in Australia. An outdoor pot experiment was conducted to examine the effects of planting time on two populations of A. retroflexus and A. viridis at the research farm of the University of Queensland, Australia. Both species were planted every month from October to January (2017 to 2018 and 2018 to 2019), and their growth and seed production were recorded. Although both weeds matured at a similar number of growing degree days (GDD), they required a different number of days to complete their life cycles depending on planting date. The growth period was reduced and flowering occurred sooner as both species experienced cooler temperatures and shorter daylight hours. Both species exhibited increased height, biomass, and seed production for the October-sown plants compared with other planting times, and these parameters were reduced by delaying the planting time. The shoot and root biomass of A. retroflexus and A. viridis (averaged over both populations) was reduced by more than 70% and 65%, respectively, when planted in January, in comparison to planting in October. When planted in October, A. retroflexus and A. viridis produced 11,350 and 5,780 seeds plant−1, but these were reduced to 770 and 365 seeds plant−1 for the January planting date, respectively. Although the growth and fecundity of these species were dependent on planting time, these weeds could emerge throughout the late spring to summer growing season (October to March) in southeast Australia and could produce a significant number of seeds. The results showed that when these species emerged in the late spring (October), they grew vigorously and produced more biomass in comparison with the other planting dates. Therefore, any early weed management practice for these species could be beneficial for minimizing the subsequent cost and energy inputs toward their control.

The marine red alga Ahnfeltiopsis triquetrifolia sp. nov. (Phyllophoraceae, Gigartinales) is described from Japan. Foliaceous unisexual gametophytes are characterized by having three-edged axes, and crustose tetrasporophytes are distinguished by the following combination of features: tightly coalescent perithallial filaments, nemathecial sori, small numbers of both tetrasporangia (3 or 4) and sterile cap cells (1 or 2) in each fertile filament, and the absence of hypobasal tissue. Gonimoblast filaments develop from the auxiliary cell after it has fused with a carpogonium. Carposporangia develop from gonimoblast cells, from medullary cells contacted by the gonimoblast filaments, and from the cells produced by such medullary cells. Mature, compact cystocarps are immersed within the medullary layer and discharge carpospores through carpostomes formed in the thickened cortex. Cultured tetrasporophytes were induced to sporulate by transfer from a long-day to a short-day regime at 20°C, and one single short-day cycle was effective for tetrasporangial induction. Tetraspore germlings gave rise to basal discs from which upright axes developed. The upright axes showed a morphology similar to that of field-collected gametophytes, although they remained vegetative during 18 months in culture.