Our results also corroborated with this finding. Our results indicated that, apart from fruits, SS were mainly accumulated in the leaves at harvest, which accounted for about 90% of the total leaf NSC. Thus, the allocation of NSCs in different organs allowed the plants to persist when respiration rate was higher than photo assimilation in annual events, but also aided in responding to abiotic stresses such as drought . Our results indicated that plants that received 100% ETc had higher NSC content. Similarly, a previous study with potted grapevines reported increased starch and SS contents in the leaves from the grapevines with higher leaf area to fruit ratio that were well-watered . In shoots, sucrose and raffinose proportions were higher in 50 and 100% ETc treatments compared with 25% ETc. As a great part of the shoot biomass is vascular tissue, this may suggest an increase in NSC translocation in these treatments. Although sucrose is the main sugar for carbon translocation through the phloem into the sink tissues, recent research highlighted the roles of other sugars, such as raffinose, in carbon translocation and storage . On the other hand, previous research reported less NSC accumulation in grapevine canes under carbon starvation at a low leaf to fruit ratios, suggesting that sucrose may control starch accumulation through adjustment of the sink strength . Furthermore, Rossouw et al. also highlighted the role of raffinose toward root carbohydrate source functioning in grapevines with significantly lower leaf to fruit ratio due to defoliation from carbon starvation . When the photosynthetic supply of carbohydrates is limited,round flower buckets remobilization from perennial tissues can provide an alternative carbon source . Thus, previous research conducted on potted grapevines reported a concurrent starch remobilization from roots with a rapid berry sugar accumulation .
Conversely, under our experimental conditions , no effect of water deficits on NSC remobilization from roots to berries was observed despite the decreased leaf to fruit ratio. Likewise, Keller et al. did not observe higher amounts of sugars in berries from field-grown Cabernet Sauvignon subjected to 25% ETc compared with 70 or 100% ETc under field conditions. Under our experimental conditions, yield per plant was strongly related to shoot, leaf, and root BM. Similarly, Field et al. found that grapevines with the lowest shoot growth rate before veraison had significantly less fruit set than the other treatments, attributing these effects to the restoration of root carbohydrate reserves that occurred at the same time. Grapevines subjected to 25% ETc had reduced photo assimilates due to lower AN in both seasons resulting in less NSC in the source leaves available for new growth and exported to sinks. This resulted in a general lower plant BM . Contrarily, grapevines subjected to 100% ETc had higher photo assimilation rates throughout the course of the study that led to higher SS and starch content and, consequently, to the improvement of BM and, therefore, higher harvest index. Therefore, the reduced growth rate of both sink and source organs in response to water deficits indicated that the availability of carbon is a major growth constraint. The yield per plant of 50% ETc was lower than 100% ETc, but not as low as 25% ETc. However, canopy BM was greatly reduced in both 50% ETc and 25% ETc compared with 100% ETc. Accordingly, Field et al. reported that grapevine grown under warm soil conditions favored shoot and fruit development over carbohydrate reserve accumulation. In contrast, Candolfi-Vasconcelos et al. reported that a lower leaf area to fruit ratio increased the translocation of carbohydrates from permanent structures to reproductive organs to support grape ripening. The shoot to root ratio revealed a positive relationship with the total BM, leaf and root NSC, and N contents. Thus, the distribution of biomass relies on the C:N ratio as highlighted by the negative relationship between shoot to root and the sucrose:nitrogen ratios. Similarly, a linear relationship between NSC and root to shoot ratio in grapevines grown under stressful conditions was previously reported .
From a molecular point of view, the alterations of source:sink ratios led to transcriptional adjustments of genes involved in starch metabolism, including the upregulation of VvGPT1 and VvNTT for lower leaf area to fruit ratios . Furthermore, enhanced root biomass in 100% ETc likely resulted from higher sugar content in the roots as our data supported. It was recently reported that increases in root elongation and hexose contents were due to the VvSWEET4 over expression, a gene implied as a grapevine response to abiotic stress . Similarly, Medici et al. reported up- or down regulation of the genes encoding hexose transporters in grapevines subjected to water deficits corroborating this result. Therefore, although some genes may be expressed under water deficit, lack of carbon accumulation impaired the growth. The relationship between root to shoot ratio and plant nitrogen content was previously reported for grapevines, suggesting that dry matter partitioning is largely a function of the internal status of the plants . We found decreased N content in grapevines facing water deficits, which resulted in a decrease of total BM. Similarly, Romero et al. reported reductions in leaf nitrogen content when vines were subjected to water deficits. These authors suggested that nutrient uptake may be reduced due to deficits in soil water profile, and the slow root growth under these conditions consequently inhibited grapevine growth. In our study, N content was strongly related to photosynthetic pigments. Accordingly, previous studies reported lower leaf N and leaf chlorophyll in deficit-irrigated grapevines, suggesting quantitative losses in the photosynthetic apparatus and/or damage to the biochemical photosynthetic machinery, decreasing photosynthetic capacity as corroborated with the lower NSC leaf content with water deficits. Finally, molecular research over the last decades has suggested the important regulatory functions of sucrose and N metabolites in metabolism at the cellular and subcellular levels and/or in gene expression patterns, giving new insights into how plants may modulate over a longer period its growth and biomass allocation in response to fluctuating environmental conditions .
Optimism is a key facet of positive psychological well-being that is associated with reduced morbidity and mortality, independent of psychological distress . Despite accumulating evidence regarding the relationship between optimism and health, underlying mechanisms remain unclear. Prior work has linked optimism with higher levels of physical activity and better physiological adjustment to stress exposure . Potential beneficial effects of optimism on physical activity and stress response may be partly a function of its regulatory component. Optimism reflects having confidence in the future, which in turn results in a greater likelihood of employing strategies for achieving one’s goals, including effortful goal engagement, problem-focused coping with challenges, and goal adjustment when goals become unattainable . The ability to employ these strategies effectively and flexibly likely provides greater means with which to confront and manage life’s challenges and to adopt more health protective behaviors. Despite increasing evidence of optimism’s relationships with more physical activity and healthier physiological responses to stress, the vast majority of studies focusing on dispositional optimism and its associations with beneficial physical and physiological outcomes have been observational . As such, the direction of the effect is unclear,plastic flower buckets wholesale leaving open the question of whether optimism causally influences physical activity or physical activity increases optimism. Additionally, almost all previous studies have relied on self-reported optimism and positive affect which may be subject to social desirability and recall bias. Experimental research in which individuals are randomly assigned to an optimism intervention with targeted pathways related to improved health as outcomes – like physical activity and stress responses – is needed to establish the causal role of optimism in relation to these outcomes. While most research has focused on trait-based optimism, a growing number of studies have considered whether optimism can be encouraged, cultivated or modified, and if health-related effects of more deliberately cultivated optimism are similar . A number of studies have used experimental methods to manipulate optimism, typically through interventions involving writing tasks . These interventions successfully increase optimism and other self reported affective responses and decrease negative affect, depression, anxiety, and aggression, but a key outstanding question is whether these interventions can also sufficiently alter behavior and physiology in ways that explain downstream beneficial health effects. While some evidence suggests positive effects of these interventions, the generalizability of these effects to healthy community-dwelling adults is unclear. For example, many experimental studies to date have been conducted among patient populations with a recent disease diagnosis or acute event such individuals tend to be highly motivated to improve their health behaviors, willing to undergo relatively intensive intervention protocols, and also relatively unhealthy at the outset and therefore have substantial room to show improvement. Other studies testing short-term optimism manipulation strategies in non-patient populations also provide some evidence that writing task interventions could improve health and well-being; however, these have been conducted exclusively within student populations which may be more compliant than the general population .
Therefore, a key outstanding question is whether optimism levels can be altered to subsequently lead to changes in downstream health-relevant processes like physical activity and stress reactivity within the general population. The overall aim of this research was to examine the effects of an optimism intervention on physical activity and stress reactivity with community volunteers. We developed a short intervention designed to induce optimism in the short-term and randomized participants either to the optimism intervention or an active control condition. The same intervention was used in both studies, and we harmonized the self-reported dependent variables. We hypothesized that: 1) the intervention group relative to the control group would show increased self-reported optimism and positive affect, as well as decreased anxiety, depression, aggression, and negative affect; 2) in Study 1, the optimism intervention compared to the control group would show more engagement and persistence with physical activity tasks, as operationalized by a stepping task and a sit-stand task and self-reported exercise beliefs including perceived benefits and barriers of exercise as well as self-efficacy of exercising; 3) in Study 2, the optimism intervention compared to the control group would show healthier stress-related physiologic responses at rest and during an acute stressor; and 4) those who were rated as more optimistic would show more engagement and persistence in physical activity tasks and have better stress-related physiologic responses in the lab.Participants ages 22–60 years old were recruited through Craigslist, Student Employment Office websites at local universities, and flyers posted on community bulletin boards. Potential participants completed a telephone screening to determine their eligibility and willingness to adhere to the study protocol. Individuals with chronic diseases like heart disease, who were pregnant, had body mass index ≥30 kg/m2 , or had a current diagnosis of clinical depression or other major mental disorders were excluded. As a goal of Study 1 was to assess whether optimism has beneficial effects on willingness to engage in physical activity, further exclusions included not being able to engage in physical activity or self-reporting regularly spending more than 60-minutes per week doing strenuous or moderate exercise. Additionally, participants were asked to refrain from eating for a half-hour and exercising for 2 hours prior to lab visits. Eligible individuals completed secure online consenting procedures through Qualtrics. Written consent for the in-lab portion of the study was obtained from participants during their lab visits.The protocol for both studies included three online writing tasks and one phone interview prior to a lab visit. In the lab, participants completed another writing task and one in-person interview. All the writing tasks and the lab study were conducted over one to two weeks . The four writing tasks for the intervention group included a values assessment, remembering past achieved goals, writing a gratitude letter, and imagining one’s best possible self, all chosen based on prior literature suggesting such interventions may lead to greater optimism levels . The control condition provided comparable demands for attention and writing but focused on neutral and less future-oriented activities. Prompts for the intervention condition writing tasks were identical in both studies; however, the first three prompts in the control condition were slightly modified for Study 2 Table 1. After completing the first three writing tasks online, participants of both studies were invited to come to the lab to complete the final part of the study. At the lab, participants completed a brief final screening to confirm accuracy of previously self reported information, an imagery task, a fourth writing task, an in-person interview, and physical activity tasks or stress reactivity tasks . For Study 1, participants were asked to engage in a stepping task and a sit-to-stand task.