Small Nuts Research Articles

Adaptability of Pecan as a Species

Pecan [Carya illinoinensis (Wangenh.) C. Koch] is indigenous to the Mississippi River drainage system of the United States. Climate in the native pecan region ranges from humid to semiarid and from mild to harsh winters. Rainfall is bimodal with peaks in March to April and in August to September. Pecan is site specific and is the climax tree species on loamy, well drained, first bottom river land with a relatively high water table. Detrimental effects from pecan's shade intolerance from its more vigorous, sympatric species are minimized as these species are specific to differ sites. Pecan's deep and phreatophytic rooting habit ensures soil moisture during drought periods and facilitates pecan's survival in semiarid regions. Root development in the humus-surface layer ensures nutrient uptake from the most nutrient rich layer of the soil and, when the lower soil profile is saturated, aeration for the roots and water and nutrient uptake. The bimodal rain pattern replenishes soil profile moisture and its timing ensures seed germination, stand establishment, well-developed seed, and minimal drought stress. Natural selection for freeze tolerance and for minimum fruit development time allows survival in areas with harsh winters and short growing seasons. Regulation of seed germination and budbreak by heating and chilling results in pecan being native in cold and warm climates, greatly increasing the native range. The northern limit for pecan is dictated by heat units; the southern limit is restricted by lack of bimodal rains and vivipary. Reproductive stress is caused by the high lipid content of seed, but is counteracted by a long juvenile growth period of the seedling, by a small nut size and low percentage kernel, and by “off” production years of the tree. Nut and percentage kernel decrease as the growing season decreases which contributes to species survival in geographical regions with a short growing season. Selection for small nuts with low percentage kernel is enhanced by predators. Tree reserves are depleted by heavy production during “on” years and are replenished during “off”years. Perpetuation of pecan forests is apparently from sib/half sib seedlings following predator satiation while dissemination into new areas may be mainly by predators. Pecan and its pests successfully co-exist. Major defense against fruit feeders is escape in time, leaf feeders by biological associations and accommodation, and leaf diseases by confrontation. Heterozygous progenies from cross-pollination provide ample genetic diversity for continuous pecan selection to endure pressures imposed throughout a wide climatic range. Ecological adaptions within native pecan forests should be used in developing and maintaining commercial pecan orchards.

Geographic variation in nut size of Castanopsis species in Japan

AbstractThe environmental conditions affecting the geographic variation in nut size of the Castanopsis species in Japan were examined. The mother trees having a relatively large nut tended to dominate in the geographically marginal area of the distribution range in Japan, i.e. the Japan Sea, Kanto, and Ryukyu areas, whereas in the central area, i.e. the Pacific area, mother trees having a relatively small nut occurred. We attempted an adaptive explanation, proposing that mother trees with large nuts have higher inclusive fitness than those with small nuts in unfavorable habitats. The Japan Sea area features large amounts of snow fall and low temperatures. The Ryukyu area is insular and is characterized by high temperatures. Within the Pacific area, mother trees with relatively large nuts were abundant at both higher and lower parts of the altitudinal range. We infer that environmental conditions in marginal areas, in terms of both horizontal and vertical distribution, favor mother trees having large nuts. However, in the marginal Kanto area, the cause of the absence of mother trees having relatively small nuts was independent of the environmental conditions. The geographic variation in nut size of Castanopsis species is not always explained by environmental factors.

Dynamics-based Damage Inspection of an Aircraft Wing Panel

This paper presents damage detection of an aircraft wing panel using dynamic responses. The panel has an irregular shape, varying thickness, seven ribs on its backside, and defects. An in-house finite element code GESA (Geometrically Exact Structural Analysis) was used to model the panel using 528 DKT plate elements and to obtain mode shapes and natural frequencies, and experimental dynamic characteristics and Operational Deflection Shapes (ODSs) were measured using a scanning laser vibrometer. Results show that numerical dynamic characteristics agree well with experimental ones. Six defects were created in the panel, including four small nuts glued on the backside and two small slots cut by electron discharge machining. Detection of the six defects was performed using the distributions of RMS velocities under high-frequency broadband periodic chirp excitations provided by a PZT patch and damage locating curves obtained by processing experimental ODSs using a newly developed Boundary Effect Evaluation (BEE) method. The BEE method is nondestructive and model-independent; it processes experimental ODSs to reveal local boundary effects caused by defects. Experimental results show that the six small defects in the panel can be pinpointed using the approach.

Dispersal and germination of big and small nuts of Quercus serrata in a subtropical broad-leaved evergreen forest

Few studies have concerned with the differences in seed dispersal, germination and seedling establishment between big and small seeds within a tree species. In this study, the dispersal and fates of big and small nuts (labeled with coded tin-tags) of Quercus serrata (a dominant canopy tree species) were monitored at two stands (a primary stand and a secondary stand) in a subtropical broad-leaved evergreen forest in the Dujiangyan Region, Sichuan Province, China. We also examined the differences in germination of big and small nuts of Q. serrata without predation by sowing nuts on the ground surface or in the soil. We found that, the big nuts were better survived with longer cache lifetime, longer dispersal distances and higher proportion of emerged seedlings (2% at primary stand, 0.5% at secondary stand) than small nuts. We also found that, there was a marginally physiological difference in germination (germination proportion and seedling height) between big and small nuts. Burial obviously improves germination of both big and small nuts. It is suggested that small rodents may act as an important selective force to affect seed fates, seed shadows and seedling establishment for big and small nut of Q. serrata.

Effects of burying depth and seed size on seedling establishment of Japanese chestnuts, Castanea crenata

The extent to which caching depth and nut size affect seedling establishment of Japanese chestnuts, Castanea crenata Sieb. et Zucc. , were investigated by burying the nuts of three different size-classes at different depths (0 cm on litter; 0, 5, 10, 20 and 30 cm beneath litter) in a nursery. Seedling emergence, seedling mass and height were usually reduced by deep burial, particularly for small nuts. With increasing burial depth and decreasing nut size, the biomass allocation to stems (particularly below ground stems) increased, while allocation to roots (part below cotyledons including hypocotyl) decreased. Such morphological changes would amortize the limited seed reserve to facilitate emergence. Seedling emergence, seedling mass and height were greatest at 5 cm burial depth, but no seedlings emerged when nuts were sown on litter, suggesting that animal caching in shallow burial (scatter hoarding) favors chestnuts regeneration. At the optimal burial depth (5 cm), there was little difference in the seedling height among nut size-classes which showed that nut size has little effect on their competitive abilities with neighboring herbs in the early successional habitats where the chestnuts usually regenerate. The fact that most of the larder- or nest-hoarded nuts ( depth≧10 cm) were consumed by wood mice ( Apodemus spp.) in the fields suggests that large nuts would not always have distinct advantages over small nuts.

American crows cache less preferred walnuts

Animals that can cache food are faced with the options of hiding or eating each food item they encounter. Empirical evidence from a few bird and mammal species suggests that the likelihood of caching may be influenced by a number of factors, including perishability, handling time, food value and the presence of potential cache robbers. American crows,Corvus brachyrhynchos , forage in large flocks for walnuts, and each nut must be either eaten immediately or transported elsewhere for caching. To examine which factors influence caching behaviour in this species, I observed free-living crows foraging for two species of walnuts at naturally occurring and provisioned sites, and documented characteristics of preferred and less preferred walnuts in dichotomous choice tests. The majority of crows flew off with their nuts and cached them in agricultural fields 1–2km away, but others stayed near the walnut trees and cracked their nuts open by dropping them repeatedly on the ground. Nuts that were transported to agricultural fields and cached were significantly smaller than those eaten on site, indicating that crows were being selective about whether to consume or cache nuts. In dichotomous choice tests crows preferred English over black walnuts, which is unsurprising as English walnuts have higher energy value and are easier to crack. When choosing within-nut species, crows preferred cracked over intact and large over small nuts, also consistent with preferences based on minimizing handling costs or maximizing energy content. When provisioned with nuts of different species, sizes and condition (intact or slightly cracked), crows were more likely to cache black and intact walnuts. They were also more likely to cache nuts later in the day. When they did cache the more preferred English walnuts, crows spent more time hiding each nut. These results suggest that crows consumed preferred nuts immediately and cached less desirable nuts.

Predation and dispersal of large and small seeds of a tropical palm

Seed size may vary greatly among individuals within plant species. What effects the extremes of this variation have for seeds taken by small mammals are poorly understood. Not all seeds removed by small mammals are necessarily eaten. Small rodents are common seed predators, but they may disperse a significant proportion of seeds by scatter hoarding them via burial. Size‐dependent predation and dispersal of seeds has not been directly tested within a plant species for tropical rodents. This study tested whether or not large and small nuts of Astrocaryum mexicanum (Palmae) differed in their fates due to handling by the spiny pocket mouse Heteromys desmarestianus (Heteromyidae). Exclosures were used to give small rodents exclusive access to A. mexicanum nuts. H. desmarestianus preferentially consumed large over small A. mexicanum nuts, but cached (in burrows and by scatter hoarding) similar proportions of these nuts by size. Small nuts tended to be buried farther away from exclosures than large nuts. Although sample sizes of buried nuts were small, the rodents retrieved all buried large nuts, but 30% of the small nuts remained buried long enough to germinate. I also examined predispersal predation by insects and found that insects appear to have no size preference for A. mexicanum nuts, but insect predation appears to hinder nut development. Thus, nuts attacked by insects develop to be significantly smaller, with a low proportion of undamaged endosperm, than uninfested nuts. It is hypothesized that the preferential predation of large A. mexicanum nuts by H. desmarestianus is a response by these rodents to insect predation.

Heritability, variance components and correlation of morphological and phenological traits in hazelnut

AbstractMost traits of interest in hazelnut are quantitative, yet there is little information available on heritability, variance components, or correlations. In this study, 13 morphological and four phenological traits were observed for 3 years on 41 parental genotypes, and for 2 years on seed‐lings representing 35 progenies. Narrow‐sense heritability estimates obtained by regression of offspring means on midparent values were all high, ranging from 0.56 for amount of kernel fibre to 0.89 for nut depth. Data on the parent genotypes was used to analyse variance components and showed that genotypic variance accounted for most of the phenotypic variance for all traits, and there was very little variation among trees within genotypes. Genotype‐year interaction accounted for only a very small part of the phenotypic variance for most traits, and changes in genotype rank were few and minor. Thus, selection based on genotype means is appropriate. The largest genotype‐year interaction components were observed for time of nut maturity, time of stigma exsertion, time of catkin elongation, number of nuts per cluster and amount of kernel fibre. For these five traits, evaluation over a period of years is advised. Correlation coefficients were large and positive for four nut size traits, indicating some redundancy in these measurements. Three of the phenological traits (time of stigma exsertion, time of catkin elongation, and time of leaf budbreak) were also highly and positively correlated. A large genetic correlation (0.44 < r < 0.73) was noted between good blanching and early phenology (catkin elongation, stigma exsertion and leaf budbreak), although plots of individual seedling values showed a large degree of scattering. Genetic correlations also indicated that seedlings with small nuts also tend to have compressed nuts, short husks and catkins that elongate later, but plots of individual seedling values showed large scattering. Correlations among the six traits directly related to the objectives of the Oregon State University hazelnut breeding programme (kernel weight, per cent kernel, nut shape index, blanching ability, relative husk length and nut maturity) were very low, indicating that they can be handled as independent traits.

Phylogeny of the genus Pistacia as determined from analysis of the chloroplast genome.

Classification within the genus Pistacia has been based on leaf morphology and geographical distribution. Molecular genetic tools (PCR amplification followed by restriction analysis of a 3.2-kb region of variable chloroplast DNA, and restriction fragment length polymorphism analysis of the Pistacia cpDNA with tobacco chloroplast DNA probes) provided a new set of variables to study the phylogenetic relationships of 10 Pistacia species. Both parsimony and cluster analyses were used to divide the genus into two major groups. P. vera was determined to be the least derived species. P. weinmannifolia, an Asian species, is most closely related to P. texana and P. mexicana, New World species. These three species share a common origin, suggesting that a common ancestor of P. texana and P. mexicana originated in Asia. P. integerrima and P. chinensis were shown to be distinct whereas the pairs of species were monophyletic within each of two tertiary groups, P. vera:P. khinjuk and P. mexicana:P. texana. An evolutionary trend from large to small nuts and leaves with few, large leaflets to many, small leaflets was supported. The genus Pistacia was shown to have a low chloroplast DNA mutation rate: 0.05-0.16 times that expected of annual plants.

PATTERNS OF ROOTSTOCK USAGE IN THE PECAN INDUSTRY

The commercial pecan [Carya illinoinensis (Wangenh.) K. Koch] nursery industry relies on open-pollinated seed for rootstock production. Current choice of seedstocks by commercial pecan nurserymen was surveyed by telephone. Nurseries were called if they appeared in the directory used for the 1994 release of `Navaho'. Factors influencing the choice of seedstock include seed availability, nut fill, nut size, nut shape, seedling vigor, stand uniformity, and root characteristics. Local availability is important in the choice of seedstock. Those who harvest from their own trees usually credit the seedstock with other valuable characteristics, such as improved germination or vigor. Those who purchase seed usually target a preferred seedstocks for particular reasons but plant available seed in its absence. Well-filled nuts are recognized as being important for good germination. Small nuts are often preferred, especially when seed is purchased because more nuts per pound increases potential production. Round nuts are generally preferred over long nuts due to improved performance in some mechanical planters. Distinct regional preferences are apparent in the choice of seedstocks. Regionally preferred seedstock selections are generally validated by a survey of the research literature. Patterns of selection are consistent with climatic and geographic constraints. Tree procurement patterns have changed: many small nurseries have gone out of business, many large nurseries transport trees far from the nursery for sales, and quarantine restrictions have altered procurement patterns in Arizona. Recommendations are made to nurserymen, pecan growers, and researchers concerning continued progress toward improving regionally adapted pecan rootstocks through seedstock selection.

229 PHYLOGENETIC RELATIONSHIPS OF PISTACIA SPECIES FROM ANALYSIS OF CHLOROPLAST DNA VARIATION

PCR amplification and restriction analysis of a 3.2 kilobase hypervariable chloroplast DNA, as well as hybridization of the entire restricted chloroplast genome with tobacco chloroplast DNA probes permitted the development of a phylogeny for 10 Pistacia species. The genus divided into two major groups. P. Vera was most ancestral. P. weinmannifolia, an Asian species, is most closely related to P. texana and P. mexicana, new world species. The 3 sp. are more recently diverged, suggesting that a common ancestor of P. texana and P. mexicana originated in Asia. P. integerrima and P. chinensis are distinct species while species within two tertiary groups were monophyletic, P. vera:P. khinjuk and P. mexicana:P. texana. A general evolutionary trend from large to small nuts and leaves with few, large leaflets to many, small leaflets was documented. Pistacia had an unusually low chloroplast DNA mutation rate, more than 20x less than expected.

Development of a solution to the debris fretting problem

One of the major recognized causes of fuel rod failures is fretting of the clad due to the entrapment of small particles of debris in a fuel rod spacer. Such debris, inadvertently dropped into the primary system during maintenance operations, includes various sizes of particles. Very small particles of the size of a grain of sand pass through the system without harm. Some larger size particles such as large bolts and nuts cannot pass through the fuel assembly inlet (lower tie plate) and thus cause no harm to the fuel rods. Intermediate size particles, however, such as metal cuttings, electrical connectors, metal fittings, pieces of wire, and small nuts and bolts can pass through the holes in the lower tie plate and become trapped between fuel rods in a spacer where hydrautically induced vibrations can cause fretting failure of the fuel rod. A Curved-Blade Tie Plate (FUELGARD™) has been developed which effectively traps the intermediate size debris before it enters the lower spacer. This specially designed tie plate greatly reduces the danger of debris damage with little or no increase in the pressure drop of the coolant flow system.

RELATIVE HARDINESS OF BLOSSOMS AND SMALL NUTS OF NINE ALMOND CULTIVARS

Almond (Prunus dulcis Mill.) cultivars vary in tolerance to cold with flowers at pink bud more tolerant than at full bloom or than small nuts. Branch samples 60 cm long with 30-100 blossoms or nuts were cut, sprayed with water, and artifically frozen. Subsamples were removed after exposure to 4 to 6 successively lower temperatures for 30 minutes. After 48 hours of ambient temperatures, flowers or small nuts were sectioned and examined for visual evidence of injury. Of the early cultivars, `Peerless', is most sensitive at full bloom and `Sonora' is most hardy. `Sonora' is especially hardy at pink bud. `NePlus Ultra' is intermediate. Of the mid-blooming cultivars, `Carmel' is most sensitive to cold while `Nonpareil' is most tolerant. `Price' is intermediate. The late blooming cultivar, 'Mission' is most sensitive while 'Padre' and 'Butte' appear similar. This study compared several popular new cultivars to older industry standards.

Timing of nitrogen application to macadamias. 3. Reproductive growth, yield and quality

Depression of flowering in macadamias (Macadamia integrifolia Maiden and Betche) was associated with low nitrogen (N) status following 1 application of N (690 g N/tree.year) in summer of the first season and in control trees (monthly applications totalling 230 g N/tree.year) in the second and third seasons. Yield responses to N were observed only in the second and subsequent seasons. Yields of commercially acceptable nuts were higher, and small reject nuts lower, than nuts produced by control trees. Nut quality from control trees was as good as, and in many cases superior to fertilised trees receiving the higher rate of N in 1 application at various times through the year. Forward stepwise multiple regression analyses indicated the importance of time and extent of vegetative flushing, total annual tree growth and carbohydrate reserves stored in tree trunks on nut yield and quality. An appreciation of these factors can be used to guide management decisions for optimum production and quality of macadamias.

Investigations on Seedling Vigour in Cashew (Anacardium occidentale L.)

AbstractSeedlings from 27 open pollinated cas‐hew genotypes in two environments with five replications in each location were used to investigate the genetic, the environmental, and the nut size effects on cashew seedling vigour during the 12‐week pretransplantation period.Enviromental variances, genotype × environment interactions, and broadsense heritability values for the eight studied traits indicated that emergence percentage (L %) and seedling height (SH) were more reliable indices for seedling vigour, since they were more heritable and less influenced by the environment. Seedlings from large cashew nuts were consistently more vigorous than those from small nuts, probably because of the larger food reserve in the two cotyledons.