D. Scott NeSmith

Nutrient accumulation and distribution of wheat genotypes in response to waterlogging and nutrient supply

The effect of soil waterlogging and nutrient supply on plant nutrient accumulation and distribution was investigated for two genotypes of winter wheat (Triticum aestivum L.) differing in waterlogging resistance, ‘Bayles’ and ‘Savannah’. Plants were grown in waterlogged or drained sand and fertilized with half-strength or full-strength Hoaglands solution.Waterlogging reduced the concentrations of N, P, K, Mg, and Zn in leaves and stems and increased the concentrations of those elements in the root system. The effects were greater for waterlogging-sensitive Bayles than for waterlogging-resistant Savannah. Higher concentrations of Fe and Mn were found in waterlogged plants compared to the control plants for sensitive Bayles. Waterlogging increased the proportion of N and Zn in the root system and decreased that of K in stems for Bayles. The proportion of Fe increased in leaves and stems for Bayles and Savannah under waterlogged conditions, but to a greater extent for Bayles. Doubling the concentrations of all major and minor nutrient elements supplied to the waterlogged rooting medium improved plant nutrient status and enhanced plant dry matter production.

Responses of squash to salinity, waterlogging, and subsequent drainage: I. Gas exchange, water relations, and nitrogen status

Abstract To examine plant physiological responses to salinity, waterlogging, and subsequent drainage, summer squash (Cucurbita pepo) was grown in well watered or flooded sand with full‐strength Hoagland solution containing 100 mol/m3 sodium chloride (NaCl) or no NaCl for 14 d. Half of the waterlogged plants were transferred to drained conditions for 7 d of recovery, while half of salinized plants were continuously salinized until 21 d. Waterlogging or salinity alone reduced photosynthetic rate (Pn), stomatal conductance (gs), and leaf chlorophyll content to a greater extent with waterlogging. Waterlogging alone, however, did not affect leaf water potential (ψ leaf) Salinity alone did not affect leaf and root nitrogen content. A combination of waterlogging and salinity exacerbated the adverse effects of each factor alone for Pn, gs, leaf chlorophyll, and nitrogen content, but not for ψ leaf. Seven days after termination of waterlogging, a full recovery occurred for gs, ψ leaf, leaf chlorophyll content, and...

Responses of squash to salinity, waterlogging, and subsequent drainage: II. Root and shoot growth

Abstract The responses of root and shoot growth to concurrent salinity and waterlogging, and subsequent drainage of summer squash (Cucurbita pepo) were studied in a greenhouse experiment. Plants were well watered or flooded with full‐strength Hoagland solution containing 100 mol/m3 sodium chloride (NaCl) or no NaCl for 14 d. Waterlogged plants were then transferred to drained conditions for 7 d of recovery, while salinized plants were continuously salinized until 21 d. Waterlogging led to greater reductions in root and shoot growth, and fruit yield than did salinity. Waterlogging stimulated production of adventitious roots; however, salinity suppressed this enhancement effect. A combination of waterlogging and salinity exacerbated the adverse effects of each factor alone on root and shoot growth. Seven days after termination of waterlogging, a full recovery occurred for number and length of adventitious roots, number of lateral roots, and root dry weight for waterlogged plants under non‐saline conditions,...

Use of Plant Growth Regulators in Blueberry Production in the Southeastern U.S.: A Review

Abstract Blueberry (Vaccinium sp.) production has expanded rapidly in the Southeastern U.S. over the past two decades, and various production problems have been encountered. These problems include poor pollination, low fruit set, freeze damage, variable yields, and small fruit size among others. Plant growth regulators (PGRs) have been utilized to overcome some production problems with some degree of success. This paper reviews findings of research that has been conducted over the past few years with PGRs and blueberries in the Southeast.

Fruit Set and Berry Weight of Four Rabbiteye Blueberry Cultivars Following Exposure to Sub-Freezing Temperatures During Flowering

Two spring freezes in Griffin, Georgia during the flowering period in 2008 provided an opportunity to monitor freeze-damage effects on fruit set and fruit weight of four rabbiteye blueberry cultivars under field conditions. Minimum temperatures ofu2009−4.2 andu2009−3.5°C occurred on March 9 and March 25, respectively. The estimated dates of 50% open flowers for the cultivars were: Climax, March 23; Alapaha, March 30; Tifblue, April 2, and Ochlockonee, April 10. Initial visual damage estimates (i.e., corolla browning) 3 to 4 days following the last freeze suggested nearly a total crop loss for ‘Climax’ and ‘Alapaha’, and moderate to severe crop loss for ‘Tifblue’ and ‘Ochlockonee’. However, more quantitative estimates of fruit set after counting several thousand flowers and fruit for each cultivar revealed different results than initially anticipated. ‘Climax’ and ‘Tifblue’ did suffer great reductions in fruit set, averaging <8% fruit remaining 6 to 8 weeks after flowering. However, ‘Alapaha’ managed to maintain fruit set of more than 36%, and ‘Ochlockonee’ fruit set was greater than 50%. There were no apparent effects of the freeze on remaining fruit weights. These data indicate that there are differences in fruit set of rabbiteye cultivars following spring freezes during flowering. Hence, growers may want to consider the more cold hardy cultivars in their planting operations if their growing areas are subject to freezes in early to mid-spring.

Fruit Development Period of Several Southern Highbush Blueberry Cultivars

Flowering and ripening times were recorded for the southern highbush blueberry (Vaccinium corymbosum) cultivars Emerald, ONeal, and Star, along with the newer University of Georgia releases ‘Camellia’, ‘Rebel’, ‘Southern Splendour’, and ‘Suziblue’ over several years at three locations in Georgia. Nearby weather stations were utilized to record temperatures for calculating chill hours and heat units during each of the years. These data were used to calculate fruit development period for the different cultivars as a function of real time (days) and thermal time (heat units). Depending on cultivar and chill hours at a location, flowering time varied as much as 29 days from year to year. Overall, ‘Emerald’ was the earliest flowering, followed by ‘Rebel’. ‘Camellia’ was the latest to flower among the cultivars. Average fruit development period for the cultivars were: Southern Splendour, 56.2 days; Rebel, 65.3 days; Suziblue, 65.5 days; Star, 67.1 days; Camellia, 68.8 days; ONeal, 71.9 days; and Emerald, 82.8 days. The shortened fruit development period of ‘Southern Splendour’ resulted in a ripening time similar to ‘Rebel’ and ‘Star’, even though flowering time of ‘Southern Splendour’ was often several days later. Using heat units instead of days did not greatly reduce the coefficient of variation associated with fruit development period. However, the mean absolute and maximum difference between observed and predicted time to ripening was improved for most cultivars when heat units were used. These data should be useful in estimating how these blueberry cultivars will perform under diverse environments.