James H. Aldrich

Amino acids as determinants of host preference for the xylem feeding leafhopper, Homalodisca coagulata (Homoptera: Cicadellidae).

SummaryHomalodisca coagulata is a highly polyphagous xylem feeder with distinct seasonal patterns in its selection of host plants. These patterns were examined in relation to the amino acid content of the xylem for four common host species; Lagerstroemia indica, Baccharis halimifolia, Prunus persica, and Prunus salicina. Xylem fluid was collected from each host species at times when numbers of feeding leafhoppers were both low and high. In each case, concentrations of amino acids were greatest when numbers were high. Similarly, comparisons between host species at given times showed that concentrations of amino acids were positively correlated with host selection. In a second study, amino acids of xylem were manipulated by budding scions of a non-preferred host (P. persica) on rootstocks of preferred (P. salinica) and non-preferred (P. persica) hosts. Morphology and phenology of the budded trees were similar to that of the scion species yet the xylem composition of amino acids was primarily dependent on the rootstock. Concentrations of amino acids and the preference of leafhoppers were roughly two-fold greater for scions of the preferred than the non-preferred rootstock. In both studies, amides (glutamine plus asparagine) were the amino acids most highly correlated with host selection. These compounds are the predominant amino acids in xylem fluid, have high nitrogen to carbon ratios, and account for a high percentage of the caloric value in xylem fluid. Many of the less abundant amino acids were positively correlated with host preference, but the correlations were less consistent and correlation coefficients were generally lower.

PLANT REGENERATION OF CREEPING BLUESTEM (SCHIZACHYRIUM SCOPARIUM (MICHX.) NASH VAR. STOLONIFERUM (NASH) J. WIPFF) VIA SOMATIC EMBRYOGENESIS

SummaryCreeping bluestem (Schizachyrium scoparium (Michx.) Nash var. stoloniferum (Nash) J. Wipff) embryogenic callus growing on solid medium was used to establish a cell suspension culture in Murashige and Skoog (MS) basal medium supplemented with 1.5 mg l−1 (6.8 μM) 2,4-dichlorophenoxyacetic acid (2,4-D), 0.2 mg l−1 (0.88 μM) 6-benzylaminopurine (BA), 0.5 mg l−1 (1.4 μM) zeatin, 0.2 mg l−1 (0.58 μM) gibberellic acid (GA3), and 10% (v/v) of coconut water (CW). Pro-embryos from suspension culture matured on semi-solid MS medium in about 18 wk, and were then cultured on semi-solid MS medium without growth regulators for 2–3 wk. Shoots were regenerated on MS basal medium supplemented with 3.0 mg L−1 (13.6 μM) 2,4-D, 1.0 mg l−1 (4.4 μM) BA, 1.0 mg l−1 (2.9 μM) GA3, 0.5 mg l−1 (2.7 μM) 1-naphthaleneacetic acid (NAA), 500 mg l−1 easein hydrolysate, and 10% (v/v) CW. Rooted plantlets were successfully accelimatized to greenhouse and outdoor conditions. Using this protocol, it would be possible to produce at least 1300 fully acclimatized plantlets annually.

Susceptibility of Cultivated Native Wildflowers to Deer Damage

Abstract Foraging preference of Odocoileus virginianus (White-tailed Deer) at ornamental plantings was compared amongst 11 wildflower species native to north Florida and south Georgia. Deer exhibited strong preference for Coreopsis floridana (Florida Tickseed), C. gladiata (Coastalplain Tickseed), C. integrifolia (Fringeleaf Tickseed), and Rudbeckia fulgida (Orange Coneflower). Browsing significantly reduced the height of Florida, Coastalplain, and Fringeleaf Tickseeds, and reduced the number of Florida and Fringeleaf Tickseed flowers. Browsing pressure remained high throughout the growing season; therefore, temporary exclosures are unlikely to offer a viable solution to damage caused by deer. Information on variation in deer preference between species and across seasons should help private landowners and public land managers make strategic decisions regarding which species to establish at residences, food plots, or roadside beautification projects.