Response of Arabidopsis thaliana and Mizuna Mustard Seeds to Simulated Space Radiation Exposures.

One of the major concerns for long-term exploration missions beyond the Earth's magnetosphere is consequences from exposures to solar particle event (SPE) protons and galactic cosmic rays (GCR). For long-term crewed Lunar and Mars explorations, the production of fresh food in space will provide both nutritional supplements and psychological benefits to the astronauts. However, the effects of space radiation on plants and plant propagules have not been sufficiently investigated and characterized. In this study, we evaluated the effect of two different compositions of charged particles-simulated GCR, and simulated SPE protons on dry and hydrated seeds of the model plant Arabidopsis thaliana and the crop plant Mizuna mustard [Brassica rapa var. japonica]. Exposures to charged particles, simulated GCRs (up to 80 cGy) or SPEs (up to 200 cGy), were performed either acutely or at a low dose rate using the NASA Space Radiation Laboratory (NSRL) facility at Brookhaven National Lab (BNL). Control and irradiated seeds were planted in a solid phytogel and grown in a controlled environment. Five to seven days after planting, morphological parameters were measured to evaluate radiation-induced damage in the seedlings. After exposure to single types of charged particles, as well as to simulated GCR, the hydrated Arabidopsis seeds showed dose- and quality-dependent responses, with heavier ions causing more severe defects. Seeds exposed to simulated GCR (dry seeds) and SPE (hydrated seeds) had significant, although much less damage than seeds exposed to heavier and higher linear energy transfer (LET) particles. In general, the extent of damage depends on the seed type.

A Simple Planting Technique for Re-establishing Trees Where Frequent Inundation Occurs.

Many of the Everglades tree islands have lost elevation over the past century and most of their trees have died such that they are now covered with herbaceous plants. This protocol describes a simple, cost-effective tree planting technique needed for restoring degraded Everglade tree islands. The design is patterned after a natural Everglades process that creates floating peat islands, which allows tree survival and growth in flooded conditions and often leads to the development of tree islands. Commercially available peat bags were used as the medium for the growth and establishment of potted native tree saplings. The pop-up configuration floated initially and provided additional elevation to minimize inundation, with a single native tree species sapling and a single tree fertilizer spike. During a 3 year study involving 105 pop-ups, most plants survived (80%) and many thrived. Determining whether this technique can establish trees on a degraded tree island will require longer studies and extensive field tests.

Investigation of long-term trends in selected physical and chemical parameters of inflows to Everglades National Park, 1977-2005.

Data of seven water-quality parameters from inflows to the Everglades National Park were collected at three monitoring stations and analyzed for temporal trends. The best-fit models for the existence of trends were evaluated. The Kolmogorov-Smirnov test was used to select the theoretical distribution which best fit the data. Simple regression was used to examine the parameters for concentration-discharge relationships. The power and linear models were found to better describe the concentration-discharge relationships. Loess trend lines indicated a similar trend period of color value change during the selected period at three stations. The sharp decrease in color after 1990 at each station is consistent with the beneficial impacts of control measures, which include Best Management Practices implementation in the Everglades Agricultural Area, water management improvement, and the construction of additional stormwater treatment areas. The existence of trend analysis was performed by using the uncensored seasonal Kendall test. Conductivity and color decreased significantly at two (S12A and S333) of three stations. Alkalinity decreased significantly at S333. A "best-fit" model was selected to describe a trend change with statistical significance; the second-order equation provides a better description of the trend. This study also indicates that by using the routinely measured water-quality parameters, it may be easier to quantify the changes in water quality to aid in making water resources management decisions.