ABSTRACT
Plant reproductive failure is a critical concern for conserving rare and endangered species that typically have low-density and sparse populations. One important factor contributing to reproductive failure is the spatial arrangement of plants within a population, which can lead to isolation and negatively affect seed production, particularly in obligate outcrossers. Additionally, plant size can compound this effect, influencing seed production via multiple processes. Here, we investigate how spatial distribution and size influence the reproductive success of Vasconcellea chilensis, an endemic-threatened papaya species in Chile. We first examined whether V. chilensis can produce seeds via apomixis using pollinator exclusion experiments. We then used Spatial Point Pattern Analysis (SPPA) in three populations to explore the spatial arrangement of plants. Finally, we assessed whether plant size and neighbor distance influence the reproductive success V. chilensis is a dioecious shrub unable to produce fruits through apomixis. The SPPA revealed significant clustering of female and male plants at different spatial scales, indicating a non-random distribution. Moreover, a significant spatial association between the sexes was observed. In two populations, closer proximity to male plants was linked to higher seed production. Our study revealed that the reproductive system of V. chilensis is susceptible to distance-dependent reproductive failure due to pollen limitation. While the species' spatial structure may partially mitigate this risk, female plants isolated from male counterparts will likely experience reduced seed set.
ABSTRACT
Seed dormancy is one of the most important adaptive mechanisms in plants, optimizing germination, seedling emergence, and establishment to ensure these processes occur when environmental conditions are favorable for plant survival and growth. Endemic to rocky environments of the southern Atacama Desert, the Austral papaya (Carica chilensis) is the papaya species with the southernmost distribution within the Caricaceae, thriving in the most extreme environmental conditions. This threatened plant exhibits low natural regeneration, primarily attributed to low germination, yet no information regarding seed dormancy release is available. In this study, we investigated the dormancy-break and germination requirements of C. chilensis. We hypothesized that if C. chilensis seeds exhibit physiological dormancy, then seeds with reduced moisture content and those treated with chemicals or growth hormones would exhibit higher germination percentages and faster germination than control seeds akin to other members of Caricacea. Our results confirmed this prediction and revealed that ultra-drying (< 3% moisture content) and treating seeds with sulfuric acid, gibberellic acid, or potassium nitrate are the most effective methods for germinating C. chilensis. Consequently, we suggest using these treatments to propagate this threatened papaya species.
Subject(s)
Carica , Germination , Plant Dormancy , Seedlings , Seeds , TemperatureABSTRACT
The aim was to analyze the effects of cardiorespiratory exercise and air pollution on cognition and cardiovascular markers in four groups of older women: the active/clean air group (AC), the active/polluted air group (AP), the sedentary/clean air group (SC), and the sedentary/polluted air group (SP). Active groups performed a training task based on progressive walking. Prior to and after the experiment, the following parameters were assessed: cognition, by Mini Mental State Examination (MMSE); maximum oxygen uptake (VO2max), estimated by the Six-Minute Walk Test (6mWT); heart rate (HR); and oxygen saturation (SpO2). There were significant differences (p < 0.05) between the AC and the SP in all the MMSE dimensions except "Registration", and in all the physiological variables (VO2max, SpO2, HR). Aerobic exercise may be a protective factor against the effects that pollution have on cognition and on the mechanisms of oxygen transport.
