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Premise: Wetland plants regularly experience physiological stresses resulting from inundation; however, plant responses to the interacting effects of water level and inundation duration are not fully understood. Methods: We conducted a mesocosm experiment on two wetland species, sawgrass (Cladium jamaicense) and muhly grass (Muhlenbergia filipes), that co‐dominate many freshwater wetlands in the Florida Everglades. We tracked photosynthesis, respiration, and growth at water levels of −10 (control), 10 (shallow), and 35 cm (deep) with reference to soil surface over 6 months. Results: The response of photosynthesis to inundation was nonlinear. Specifically, photosynthetic capacity (Amax) declined by 25% in sawgrass and by 70% in muhly grass after 1–2 months of inundation. After 4 months, Amax of muhly grass in the deep‐water treatment declined to near zero. Inundated sawgrass maintained similar leaf respiration and growth rates as the control, whereas inundated muhly grass suppressed both respiration and growth. At the end of the experiment, sawgrass had similar nonstructural carbohydrate pools in all treatments. By contrast, muhly grass in the deep‐water treatment had largely depleted sugar reserves but maintained a similar starch pool as the control, which is critical for post‐stress recovery. Conclusions: Overall, the two species exhibited nonlinear and contrasting patterns of carbon uptake and use under inundation stress, which ultimately defines their strategies of surviving regularly flooded habitats. The results suggest that a future scenario with more intensive inundation, due to the water management and climate change, may weaken the dominance of muhly grass in many freshwater wetlands of the Everglades. [ABSTRACT FROM AUTHOR]

The rootstock is an essential element for orchard management, influencing scion growth, nutrient concentration, and fruit quality. Seasonal variations in leaf nutrients of 'UFSun' grafted on five different rootstocks ('Flordaguard', 'Barton', 'MP-29', 'P-22', and 'Okinawa') were investigated during the 2017-18 growing season in Citra, FL. There was no significant variation in the macronutrient concentrations (N, P, K, Mg, Ca, and S) among different rootstocks; however, 'UFSun' on 'Okinawa' and 'Flordaguard' showed greater concentrations of Ca, K, and Mg concentration than other rootstocks. In contrast, 'Flordaguard' showed less potential to accumulate P as compared with other rootstocks. The Ca concentration was lowest in 'MP-29' and 'Barton' in April and June. The concentration of macronutrients (N, P, K, Mg, Ca, and S) in leaves was greater in April and October than in December and June. With respect to rootstocks, macronutrients in December and June were the highest in 'Okinawa' and the lowest in 'Barton'. In April, the lowest concentration of macronutrient was recorded in 'Barton', whereas the highest concentrations were found in 'P-22', 'Okinawa', and 'Flordaguard'. The highest leaf micronutrient concentrations were found in 'MP-29' and 'Barton', and the lowest in 'Okinawa' and 'Flordaguard' in June and October. For all rootstocks, concentrations of micronutrients increased between leaf growth in April and senescence in October. The micronutrient concentrations of leaves decreased during December. The widest dynamic changes during the vegetative cycle were found on 'P-22'. Seasonal trends were more consistent for micronutrients than for macronutrients. [ABSTRACT FROM AUTHOR]

Asian citrus psyllid (Diaphorina citri Kuwayama) transmits a bacterium 'Candidatus Liberibacter asiaticus' (CLas) putatively responsible for a devastating citrus disease known as Asiatic huanglongbing (HLB) (citrus greening disease). The psyllid and disease have invaded many citrus-growing regions including the United States, where the disease is seriously jeopardizing the Florida citrus industry. We recently concluded research that showed CLas transmission rates are increased when citrus flush is present. Flush is any new leaf growth ranging in development from first emergence up until the leaves are fully expanded yet still tender. In an experiment with seedlings of a rootstock cultivar 'US-942', a 1-wk infestation of 20 Asian citrus psyllids from an infected colony resulted in 53–60% of seedlings becoming infected when flush was present compared with only 7% when no flush was present. In a second experiment with 'US-942', 77–97% of seedlings became infected when flush was present compared with 40% when no flush was present. A similar experiment with 'Valencia' sweet orange resulted in 23, 80, and 3% seedlings becoming infected when young, older, or no flush was present, respectively. Young plants are therefore more likely to contract HLB if flush is present, with older flush promoting higher infection rates under the conditions of this study. Based on this finding, healthy citrus should be protected from Asian citrus psyllid infestations throughout a flush. To evaluate germplasm for CLas resistance, inoculations using infected Asian citrus psyllid would best be achieved if flush is present. [ABSTRACT FROM AUTHOR]

The article presents a study regarding the leaf growth of the seagrass Syringodium filiforme in Florida Bay, Florida. It examines three types of leaf growth dynamics including growth of emergent leaves (EL method), intensive repeated measurements (RM), and demographic allometric age reconstruction techniques (DA). The three methods were used to examine the dynamics of the leaf growth among plants with various morphologies at specific water sites, such as the shallow water banktop and deeper water environment, in Florida Bay. A detailed discussion regarding the conducted evaluation and comparison of samples is also provided. Meanwhile, the results of the laboratory work revealed that the most preferred technique to study the leaf growth in S. filiforme is the EL method

Leaf growth, biomass and production of Thalassia testudinum were measured from January 1995 to March 1996, for a monospecific population in the Indian River Lagoon (IRL; Florida). Seasonal pattern of shoot biomass was characterized by low values during late winter (minimum of 0.17 g dw shoot-1 in March) and high values in mid-summer (July; 0.32 g dw shoot-1). Production of new leaves followed a pattern similar to shoot biomass, although maximum production of leaves occurred slightly earlier (late May; 0.07 leaves shoot-1 day-1) than did maximum leaf elongation and biomass accumulation (July; 3.63 cm shoot1 day-1 and 0.007 g dw shoot-1 day-1). Shoot densities (m-2) were low by the end of winter (390 50.7 SE) and high in late summer (840 201 SE), thus resulting in a measured standing stock variation between 197 and 328 g dw m-2. Annual shoot production amounted to 890 g dw m-2 and biomass turnover was 3.6. Compilation of data from the literature with results from this study showed T. testudinum leaf production was related to standing stock (p < 0.0001) by a factor of 0.016. Average daily production vs. biomass (P/B) slightly increased at lower latitudes. However, latitude only explained 34 % of the variation in P/B, other ecological factors (e. g. light or nutrient limitation) may play a major role in determining biomass and primary production for this species. Based on latitude alone, maximum potential production for Thalassia testudinum in the IRL (close to the northern limit of distribution for this species) would be up to 30 % lower than the values expected at the southern limit of distribution of this species. [ABSTRACT FROM AUTHOR]

Simple Summary: Scirtothrips dorsalis, chilli thrips, is an invasive insect species in Florida and an important foliar pest of blueberry. Sound knowledge of insect distribution within the field is needed to formulate accurate sampling methods. Fourteen blueberry fields were systematically sampled for chilli thrips during the summers of 2017 and 2018. Field counts were modeled in various spatial models and determined chilli thrips had temporally stable aggregated distribution. A fixed-precision sampling plan was developed for summer sampling, requiring seven and three sampling units (sampling unit = 10 young blueberry shoots) to estimate a nominal mean density of 20 chilli thrips with a precision of 25% and 40%, respectively. The sampling plan can be used to improve the timing of control measures and assess the effectiveness of these control measures. Scirtothrips dorsalis Hood is an invasive and foliar pest of Florida blueberry that reduces plant growth by feeding on new leaf growth. A sampling plan is needed to make informed control decisions for S. dorsalis in blueberry. Fourteen blueberry fields in central Florida were surveyed in 2017 and 2018 after summer pruning to determine the spatial and temporal distribution of S. dorsalis and to develop a fixed-precision sampling plan. A sampling unit of ten blueberry shoots (with four to five leaves each) was collected from one blueberry bush at each point along a 40 × 40 m grid. Field counts of S. dorsalis varied largely ranging from zero to 1122 adults and larvae per sampling unit. Scirtothrips dorsalis had aggregated distribution that was consistent within fields and temporally stable between summers, according to Taylor's power law (TPL) (aggregation parameter, b = 1.57), probability distributions (56 out of 70 sampling occasions fit the negative binomial distribution), Lloyd's index (b > 1 in 94% occasions), and Spatial Analysis by Distance IndicEs (31% had significant clusters). The newly developed fixed-precision sampling plan required 167, 42, seven, or three sampling units to estimate a nominal mean density of 20 S. dorsalis per sampling unit with a precision of 5%, 10%, 25%, or 40%, respectively. New knowledge on S. dorsalis distribution will aid in evaluating the timing and effectiveness of control measures. [ABSTRACT FROM AUTHOR]

• Periphytic loads decreased the growth of Vallisneria americana. • The effects of periphytic loads varied with levels of incident light and leaf age. • Loads of 4–5 mg dry mass cm−2 of leaf predicted to cause detrimental effects in full sunlight. Proliferation of nuisance algae in aquatic ecosystems is an increasingly common, global problem that can be attributed to a broad suite of anthropogenic activities. One particular concern is that algae can shade rooted vascular plants, decrease their productivity, and, in extreme cases, cause mortality and a loss of the ecological services they provide. The loss of macrophytes in Florida's iconic spring-fed systems is especially alarming. In the Chassahowitzka River, for example, increases in epiphytic algae correlated with reductions in the abundance of important macrophytes such as Vallisneria americana. However, the relationships between loads of epiphytic algae and associated periphyton and the growth of vascular plants have not been characterized adequately. Here, we quantified the effect of epiphytic algae and associated periphyton using direct, in-situ measurements of growth rates for V. americana. Periphytic loads ranged from 11 to 15,211 mg DM per shoot (0.08 to 32.37 mg DM cm−2 of leaf), and weekly growth rates ranged from 0 to 197 mg DM or 0 to 87 cm2 per shoot (0 to 94 mg DM or 0 to 39 cm2 per leaf). Data indicated that changes in the growth rates of V. americana were the consequences of combined stresses from environmental factors (e.g., light at the water's surface and periphytic loads) and physiological factors (e.g., leaf age). Life spans were shorter and turnover rates were faster only when shoots were exposed to higher periphytic loads throughout their lives. Boundary analyses of data for growth of leaves identified a threshold of 4–5 mg DM cm−2 of leaf in full sunlight, with heavier periphytic loads considered detrimental, and that threshold indicated that 20%–26% of incident, full sunlight was the minimum light requirement for V. americana in the Chassahowitzka River. A threshold for periphytic loads represents a valuable indicator that complements data on water quality, and the method to calculate a threshold provides a valuable tool that can improve management of all aquatic systems where the effects of periphyton on macrophytes are of concern. [ABSTRACT FROM AUTHOR]