Phloem anatomy is influenced by both the climate that plants have adapted to and the climate plants experience during the growing season . This suggests that more work is needed to evaluate how plastic responses to interannual or geographic variability to climate influence cultivar differences in phloem anatomy and sugar transport capacity. In Arabidopsis, the effects of growing conditions on phloem anatomy depended strongly on the climate the genotypes evolved in. Comparisons between cool and hot growing conditions showed that high temperatures reduced the proportion of phloem area in the minor veins, and that these reductions were larger in Arabidopsis genotypes that evolved in cool than hot climates . These results suggested that phloem plasticity in response to growing conditions outside evolved temperature ranges was greater ingenotypes adapted to cool climates, increasing genotypic differences in phloem anatomy under hot growing conditions. Interestingly, we found the opposite pattern in grape, that phloem area in the pedicel and petiole was significantly larger in the cultivars typically grown in warm than hot climates, even though our common garden experiment was in a hot growing region . Comparisons in different regions or in years with different climatic conditions are needed to determine how strongly the cultivar differences in anatomy observed here depend on the conditions during phloem development.Xylem and phloem area scaled in the midvein, petiole, and pedicel,wholesale planter containers which produced similar relationships in xylem and phloem areas with maximum °Brix accumulation rates and climate groupings .

The relationships with xylem area could simply reflect selection for phloem traits and developmental constraints that make xylem and phloem differentiation proportional, or both xylem and phloem area could impact °Brix accumulation rates. °Brix is a concentration and determined by water and sugar contents. The phloem supplies most of the water to the berries after veraison . The total volume of phloem water influx is generally much larger than the volume of the berries, forcing the berries to export water to the canopy through the xylem to avoid cracking or splitting . A larger phloem area would increase the water influx into the berries, which could require a larger xylem area to compensate for water export. Further, the xylem accounted for most of the vascular area in each organ, and the ratio of xylem to phloem area increased with stem cross sectional area, which also made this ratio significantly larger in warm- than hot-climate cultivars . This larger xylem:phloem ratio could accelerate °Brix accumulation by increasing the capacity for water export relative to influx. Thus, selecting for a lower xylem:phloem ratio could slow berry sugar accumulation. Xylem and phloem areas also scale in other species, including ash , Pelargonium , fir , poplar, and ginkgo , and, notably, xylem: phloem ratios were smaller in species with larger fruit . However, some grape cultivars produce blockages in the pedicel xylem during ripening that reduce conductivity and water efflux, which could make the ratio of xylem to phloem area less important to °Brix accumulation rates. Overall, more work is needed to clarify the effects of individual tissue areas and xylem: phloem area ratios on ripening.Another interesting findings from the current study was that sieve element area was a significant predictor of brix accumulation rate , while porosity of the elements , most of the smaller sieve element area/ lower brix accumulation rate cultivars were from the warm climate category.

These findings suggest that grapevines have primarily adapted to control sugar accumulation rate by changing the number and width of sieve elements, although these two traits were not correlated . Conversely, phloem cross sectional area and mean sieve element area were correlated in the pedicels for other species, including pumpkin and tomato . However, similar to our findings, variation in sieve element area was small for pumpkin, and the differences between cultivars were not significant . Sieve plate porosity was significantly lower in the temperate-climate cultivars . Cooler growing regions are typically more humid and prone to disease pressure , and less porous sieve plates can facilitate the faster formation of callose blockages to more quickly restrict pathogen spread through the phloem . Future work may consider the transcriptional abundance of sugar unloading proteins , and how this relates with phloem anatomical characteristics related to pathway resistance.Phloem anatomy was a stronger predictor of berry sugar accumulation rates than vegetative physiology parameters capturing vine carbon gain and water status. This was unexpected, since photosynthesis determines the carbon available for ripening, and water stress has been shown to strongly impact sugar accumulation rates in many of the cultivars tested here . However, our experimental vines were irrigated during the ripening period to maintain leaf water potentials in a relatively narrow range . This irrigation regime follows standard commercial practices for California, which could have limited cultivar differences in vine water stress and photosynthesis and thus, their impacts on sugar accumulation. These findings suggest that measuring phloem anatomy could provide more insight into plant capacity for berry sugar accumulation under standard, irrigated conditions than conventional vegetative physiology traits. Alternatively, leaf-level photosynthesis could have been decoupled from °Brix accumulation by variation in vine balance , which would impact the ratio of whole-plant carbon supply to demand.

A larger ratio of canopy area to fruit mass would increase maximum °Brix accumulation rates. Future work should estimate leaf area per cultivar to ensure that relationships between phloem anatomy and maximum °Brix accumulation rates scale with variation in vine balance.Overall, we found that phloem cross-sectional area in the petioles and pedicels was the most predictive trait for the maximum rate of sugar accumulation in the berries across wine grape cultivars tested. Carbon dioxide in the atmosphere is expected to double by centuries’ end, and the dual effects on plant carbon availability and growing season temperature are projected to strongly accelerate sugar accumulation and exacerbate the detrimental impacts on wine quality . We suggest that reduced phloem areas could be a useful and novel phenotype to screen for in existing cultivars to slow carbon transport rates in hotter growing regions, allowing more time for flavor development. If petiole phloem area is well-conserved across life stages and under different growing conditions, this would be an especially useful trait to accelerate phenotyping since grapevines must mature for several years to begin producing fruit. However, future work is still needed to clarify how xylem area and vine balance influence sugar concentrations, and how interannual and site-specific environmental variability influence anatomical traits and sugar accumulation.Age-related macular degeneration is the leading cause of blindness among seniors in developed countries, and third worldwide after uncorrected refractive errors and cataracts. In early stages, the disease is characterized by small to intermediate drusen with pigmentary changes that may progress rapidly to more advanced forms such as choroidal neovascularization or central geographic atrophy with loss of central vision. Lutein , zeaxanthin , and the isomer meso-zeaxanthin are macular pigments that filter damaging blue light and provide oxidative defense in the macula. These pigments are found in plants as xanthophylls, with increased dietary intake proposed to reduce the development and progression of AMD. The relative concentration of xanthophyll carotenoids in the retina can be measured non-invasively by psychophysical and objective methods, expressed as macular pigment optical density. Numerous epidemiological studies report that individuals with a low MPOD level are at an increased risk of AMD . Dietary L and Z are found in certain fruits and vegetables with red, yellow, or orange color, egg yolk,plastic pot manufacturers and in some green leafy vegetables. The dietary intake of Z is lower than L in all age groups and ethnicities in the U.S.. Dietary intakes of L and Z are strongly associated with their serum levels, as well as with MPOD. Previous studies have shown that high intakes of these carotenoids from dietary sources or supplements can increase plasma L and Z, and MPOD. Once early AMD has progressed to the intermediate stage, dietary supplements are indicated, but no clinical evidence yet exists for interventions that can address the prevention of small-intermediate drusen with pigmentary changes, the initial clinical signs of macular disruption. Goji berry , also termed wolfberry or Go Chi Zi, has been used in traditional Chinese medicine for more than 2000 years. The bright red berry contains the highest amount of Z among all known dietary sources and is mainly present in a dipalmitate form. The intake of zeaxanthin dipalmitate extracts from goji berry increases plasma Z to a greater extent than non-esterified Z supplementation. The berries also contain unique carbohydrates that are present as conjugates with peptides or proteins, which are often referred to L. barbarum polysaccharides . These have shown anti-inflammatory and neuroprotective effects in animal and cell culture studies. The typical adult human eye has approximately 2.4 times more Z than L in the central fovea of the macula, making goji berry intake a prime candidate for increasing MPOD.

Nevertheless, there is a paucity of clinical evidence on goji berry and MPOD particularly for the prevention or delay of progression from early to intermediate AMD. In individuals from China with signs of early AMD, 25 g of daily consumption of goji berries for 90 days significantly increased both serum Z and MPOD. However, this study had a broad age range , some participants smoked, and others had certain preexisting medical conditions. Additionally, the authors only reported central MPOD values up to 0.5 retinal eccentricity , whereas macular pathology and visual dysfunction in AMD may extend beyond that central region. Therefore, to provide a more complete understanding of the influence of goji berry intake on the progression AMD, data is needed on for different population groups that measures MPOD at eccentricities over the entirety of the macula. In the current study, we prospectively evaluated if the daily intake of 28 g of goji berries or a commercially available supplement providing 6 mg of L and 4 mg for 90 days can improve MPOD and skin carotenoid levels, an index of total carotenoid intake, among healthy middle-aged adults, 45 to 65 years old, with no signs of drusen or early AMD. Eighty-eight volunteers, ages from 45 to 65 years old, were recruited from an online website and public advertisements in the area of greater Sacramento, California. Participants provided informed consent and were screened with a questionnaire. Inclusion criteria were being generally healthy , having a normal macular condition as verified by an optometrist, and if relevant, being prescribed the same medication regimen for at least 6 months that was not related to carotenoid metabolism and was approved by the study physician. Exclusion criteria were a dislike of, or allergy to goji berries, diseases of the eye, malabsorption problems, substance or alcohol abuse, smoking, drugs for management of lipids, glucose, or blood pressure, use of dietary supplements other than multivitamins and minerals that provided greater than 100% of the U.S. Dietary Reference Intake, or any supplement containing L or Z. The intervention was registered on ClinicalTrials.gov , with the first posted date of 6 December 2019, complied with the tenets of the Declaration of Helsinki, was approved by the Institutional Review Board of the University of California , Davis and was conducted at the UC Davis Ragle Human Nutrition Research Center. Twenty-eight grams of goji berries is considered a single serving size. The berries in this study were USDA-certified organic goji berries grown in the Ningxia region of northern China and provided by Navitas Organics, Novato CA, USA. The goji berries were portioned into clean, single-serving plastic bags and provided in 45-day allotments. The commercially available supplements were purchased online, contained 6 mg of L and 4 mg of Z per serving and were repackaged into 45-day supplies in clean plastic bottles. Habitual dietary information was collected with the Automated Self-Administered 24 h dietary assessment web-based tool once between day 0 and 45, and once again between day 45 and 90. The MPOD was assessed by the psychophysical method of customized heterochromatic flicker photometry using a macular densitometer . After participants viewed a 5-minute video detailing the measurement procedures, they were dark-adapted for 7 minutes and then began the test. The light intensity of each relevant wavelength was calibrated with a photodiode. The flicker frequency was selected based on a preliminary test of the participant’s sensitivity.