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One interesting observation of perceptual learning is the asymmetric transfer between stimuli at different external noise levels: learning at zero/low noise can transfer significantly to the same stimulus at high noise, but not vice versa. The mechanisms underlying this asymmetric transfer have been investigated by psychophysical, neurophysiological, brain imaging, and computational modeling studies. One study (PNAS 113 (2016) 5724–5729) reported that rTMS stimulations of dorsal and ventral areas impair motion direction discrimination of moving dot stimuli at 40% coherent (“noisy”) and 100% coherent (zero-noise) levels, respectively. However, after direction training at 100% coherence, only rTMS stimulation of the ventral cortex is effective, disturbing direction discrimination at both coherence levels. These results were interpreted as learning-induced changes of functional specializations of visual areas. We have concerns with the behavioral data of this study. First, contrary to the report of highly location-specific motion direction learning, our replicating experiment showed substantial learning transfer (e.g., transfer/learning ratio = 81.9%. vs 14.8% at 100% coherence). Second and more importantly, we found complete transfer of direction learning from 40% to 100% coherence, a critical baseline that is missing in this study. The transfer effect suggests that similar brain mechanisms underlie motion direction processing at two coherence levels. Therefore, this study’s conclusions regarding the roles of dorsal and ventral areas in motion direction processing at two coherence levels, as well as the effects of perceptual learning, are not supported by proper experimental evidence. It remains unexplained why distinct impacts of dorsal and ventral rTMS stimulations on motion direction discrimination were observed.

The occurrence of nectarlessness flowers in nectar‐producing plants is a common and stable phenomenon in many species, but their occurrence is still not well understood. The aim of this study is to examine a question from both the plant and pollinator perspectives: why do nectar‐producing species produce some nectarless flowers within a plant? We investigate the distribution patterns of nectarless flowers in natural populations and their variation among the populations and years in a spring‐flowering self‐incompatible perennial herb plant, Corydalis ambigua Chem. & Schlecht (Fumariaceae), we observed the foraging behavior of bumblebees to nectariferous and nectarless inflorescences. We also examined the differences in reproductive success between inflorescence types and the effect of nectar production on flower production of the next flowering season. The results indicated that the frequencies of nectarless flowers varied among inflorescences, individuals, and populations and between years. Plants can revise or keep their inflorescence types or change nectar production status in the next growing season. Bumblebees visited both types with equal frequency but different foraging behavior, which resulted in lower seed production in nectarless inflorescences. However, nectarless inflorescences may save more energy and result in larger bulbs, which produce more flowers in the next flowering season. We found that although nectarless flowers resulted in lower seed set in nectarless inflorescence or individuals, they could affect bumblebees’ foraging behavior and further promote the effective output of pollen. In addition, the resource savings could enhance plant reproductive success in the next flowering season.

Varied nutrient sources can influence the plasticity of reproductive strategies in monoecious species differently. We examined the plasticity of sexual and clonal reproductive components in distinct nutrient sources in a monoecious species, Sagittaria graminea Michx. The results showed that for aboveground reproductive components, in rich-phosphorus and low-nitrogen conditions, the species produced more male flowers, whereas female flowers did not significantly increase in number compared to low-phosphorus and low-nitrogen conditions (control). In rich-nitrogen and low-phosphorus conditions, the species produced more flowers, particularly female, and more seeds, compared to the control conditions. In the rich-nitrogen and rich-phosphorus conditions, plants increased male flowers, female flowers, total flower number, synchronously, as well as seed production. For the belowground reproductive components, in the rich-phosphorus conditions, the plants produced bigger corms than in the rich-nitrogen and control conditions, which further enhanced their competitiveness against companion species. In rich-nitrogen conditions, the plants produced more medium and small corms, and relatively more and longer stolons, which were useful in expansion and invasion of more space. Furthermore, the species displayed trade-off relationships between the aboveground and belowground reproductive components in unbalanced nutrient conditions (add-N or add-P). However, in low nutrient levels (control) or in nutrient abundant (add-N + P) conditions, there were no significant trade-off relationships between the aboveground and belowground reproductive components, based on quantities.

Demographic variation of gender expression among four natural populations and one cultivated in a monoecious species, Schisandra chinensis (Schisandraceae), was studied over three consecutive years in a bid to clarify its sexual system and to better understand reproductive strategies in monoecious plants. We found that gender expression was more variable in the natural populations than in the cultivated one. In the natural populations, plant size was positively correlated with flower production (total, male and female) but not with the female ratio, whereas shade intensity was negatively correlated with the female ratio. In the cultivated population, plant age was positively correlated with flower production and the female ratio within an age range. Hence, gender expression and reproductive output in Schisandra chinensis was found to be age-dependent. The female ratio varied with age; young and old plants had lower female ratios. Our study confirmed the sexual system in the species to be monoecy as opposed to dioecy, and supported the hypothesis that monoecious plants can regulate gender expression by altering quantities of pistillate and staminate flowers at the individual plant level to maximize fitness.

Floral color changes are common in Weigela and the retention of post-change flowers has been interpreted as a mechanism to increase attractiveness from a long distance and shorten pollinators’ lingering time on the inflorescence(s) of individual plants. In the present study, we investigated the temporal pattern of floral color change and time required for pollen tube growth in the shrub Weigela japonica var. sinica. Over the 4-day anthesis, the color of the corolla in this species changes from white to red and the color cue changes from yellow to purple. The duration of both the white phase and the intermediate phase is approximately 1 day and the duration of the red phase is approximately 2 days. Our studies showed that color change in Weigela japonica var. sinica is age-dependent but independent of pollinator visits and flower pollination. Post-change flowers lost most of both the male and female residual reproductive ability and retained no rewards for pollinators. It took at least 3 days for a pollen tube to grow to the ovules and achieve fertilization. Thus, retention of post-change flowers is necessary for the completion of pollen tube growth. Our results indicate that the temporal pattern of color change and time requirement for pollen tube growth are most likely related events.