Hickories are deciduous woody perennials of the genus Carya ( Elias, 1980 ). Most are stately trees of medium to large size, exhibiting grand ornamental features that justify their use as shade trees. All are recognized for their large
The genus Carya comprises 20 taxa globally, with 14 species found in North America ( Wood and Grauke, 2011 ). Divided into three subgenera, the “true hickories” (sect. Carya) and “pecan hickories” (sect. Apocarya) comprise the 14 species found
`Oconee' pecan (Carya illinoinensis (Wangenh.) K. Koch) was grafted on seedling rootstocks from nine open-pollinated seedstocks. Rootstocks included three seedstocks each of pecan, water hickory (C. aquatica (F. Michaux.) Nutt.) and their hybrid, Carya X lecontei (Little). Pecan seedlings had the largest basal diameter, water hickory seedlings the smallest, and hybrid seedlings were intermediate. Seedlings of `Elliott' and 'Curtis' seedstocks were larger than seedlings from `Moore' seedstock. Pecan and hybrid seedlings were more successfully grafted than water hickory. Graft success varied between seedstocks of the hybrid, with some as high as pecan. Foliage color of seedlings, indicative of iron nutrient status, was influenced by the species of rootstock: pecan seedlings were darker green than water hickory seedlings, but were inseparable from hybrid seedlings. `Oconee' scions on pecan seedlings were darker green than when grown on hybrid seedlings.
Polygalacturonase (PG) in higher plants has been considered to be associated with ripening fruits although it is now known to be present in foliage and storage organs. We recently found very high levels of PG in some grass pollens (Plant Science 59, 57-62, 1989). This prompted an examination of other pollens for PG activity. All of the pollens analyzed contained PG but the range of activities was great. Eastern cottonwood pollen contained the most PG, with a level about 12 times higher than that usually found in ripe tomato fruit. Pollens from the other members of Populus were generally high in PG. Pollens from the oak family also contained very high PG, with the highest amount in white oak pollen. Pollens from pecan, English walnut, willows, birch and hickories contained moderate levels of PG. The lowest amounts of PG were found in pollens from beech, sycamore and conifers. The PG's from the two richest sources (eastern cottonwood and white oak pollens) were partially purified and characterized. Both enzymes were found to be exopolygalacturonases that require Ca2+ for activity. PG may be involved in some function related to pollination but an explanation for the wide range of activities indifferent pollen is not obvious.
enclosed in a dehiscent husk that splits along more or less winged sutures to release the hard-shelled nuts. Nuts are tan to brown, mottled with black stripes at the apex and spots at the base. Shells are relatively thin as compared with most hickories, and
1 Research Horticulturist and Curator, National Clonal Germplasm Repository for Pecans and Hickories. 2 Professor. 3 Professor. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations
Florida Agr. Expt. Sta. J. Series no. R-01597. The assistance of David Brown and support by Kimberly-Clark, Roswell, Ga., and Reemay, Old Hickory, Term., are appreciated. The cost of publishing this paper was defrayed in part by the payment
Educational and research opportunities utilizing native plant species are being developed by the LSU Agricultural Center through the recent establishment of a native plant arboretum at the Calhoun Research Station. Plants indigenous to Louisiana and surrounding states are being collected and planted in the arboretum for evaluation of potential values for landscaping, in food industries, and/or wildlife management. Native trees being studied include species of oak (Quercus), maple (Acer), hickory (Carya), and dogwood (Cornus). Lesser known species of holly (Ilex) and hawthorn (Crataegus), are being evaluated for commercial production and landscape potential. Fruit being collected for field orchard studies include mayhaw (Crataegus opaca), pawpaw (Asimina triloba), and several native plums (Prunus spp.).
A control burn was conducted in a mixed black oak—white oak—post oak stand to determine the effectiveness of fire at removing midstory and understory trees. The midstory and understory was predominately invading species of red maple, dogwood, black cherry, black gum, and mockernut hickory with lesser amounts of canopy species—black oak, white oak, post oak, and blackjack oak. A total of 17,000 stems/ha were top killed. All stems below 10 cm (15,600 stems/ha) were killed and all of the invading species were all top killed. Large black oak (greater than 20 cm) were killed by hypoxylon which may or may not have been related to fire. Soil pH increased from 4.6 (before) to 5.7 after the burn. The litter layer was almost completely removed. The biomass of the litter layer the year after the burn was 23% of the biomass before burning. Herbaceous plants began to invade the site in the first summer.
Several new management tools and management practices are being developed for pecan. Major insect pests of pecan are pecan nut casebearer, hickory shuckworm, and pecan weevil. Sex pheromone attractants are being developed for each of these pests that improve monitoring. Also, a pecan weevil trap (Tedder's trap) was introduced recently that is more sensitive to weevil emergence than the previous trap. New models that predict critical periods for pecan scab infection are being tested. Certain legume ground covers are being tested to increase beneficial arthropods in the orchard for aphid control, and to supply N. Mulches are being investigated as an alternative to herbicide management for young trees. A mechanical fruit thinning method has been developed that increases fruit quality and reduces alternate bearing as well as stress-related disorders.