Non-fruiting Trees Research Articles

Fruit, Minerals, and Forest Elephant Trails: Do All Roads Lead to Rome?1

Tropical forests are among the most heterogeneous environments on earth, and food resources for many animals are patchy both in time and space. In Africa's equatorial forest, permanent trails created and maintained by forest elephants are conspicuous features. Trails may be several meters wide and continue for tens of kilometers. Speculation on which resources determine the distribution of trails has identified fruit, browse, and mineral deposits as candidates. In this study, the relationships between these habitat variables and elephant trails were investigated. The size of individual trails and the density of the trail system increased dramatically with proximity to mineral deposits. Fruit tree basal area decreased with perpendicular distance from trails, while that of non-fruit trees did not. Fruit tree abundance and basal area were significantly higher on trail intersections than random sites and increased with intersection size. No relationship was found between monocotyledon browse abundance and elephant trail system characteristics. Clumped resources, which are at least partially reliable, provide a high nutritional payback, and are not rapidly depleted and can thus be visited repeatedly, appear to influence permanent trail formation by forest elephants. Permanent trails may allow naive individuals or those with imperfect knowledge to locate and acquire important resources.

Characterization of a type II chlorophyll a/b-binding protein gene (Lhcb2*Pp1) in peach. II. mRNA abundance in developing leaves exposed to sun or shade.

Leaf development of shoots exposed to full sunlight and shoots shaded by the canopy was followed in field-grown, mature peach trees (Prunus persica (L.) Batsch, cv. Loring) during the first half of the 1995 growing season. The architecture and size of shaded shoots and sun-exposed shoots differed significantly. Total number of leaves produced on shaded shoots was significantly less than on sun-exposed shoots throughout the season, and differences in leaf number between light conditions increased as the season progressed. The overall patterns of leaf development along sun-exposed and shaded shoots were qualitatively similar. The expression pattern of the type II chlorophyll a/b-binding protein gene, Lhcb2*Pp1, determined by RNA abundance in leaves at different positions along the shoot, was also similar between the two light conditions. The major difference between sun-exposed and shaded leaves was a lower abundance of Lhcb2*Pp1 RNA in mature, shaded leaves compared with sun-exposed leaves. Although the number of fruit per shoot was significantly lower on shaded shoots than on sun-exposed shoots, the rate of fruit drop was not substantially different during the growing season, indicating that quantitative differences in leaf initiation and growth caused by differences in light exposure did not adversely affect fruit retention. However, based on comparison with a previous study of leaf development in non-fruiting trees, reproductive development slowed the rate of vegetative growth without affecting the overall pattern of leaf development along the shoots.

果実発育時のオウトウ樹における環境条件および樹冠構成要素が光合成および光合成産物の転流に及ぼす影響

The net photosynthetic rate of the current shoot leaves of sweet cherries (Prunus avium L.) at 40d after full bloom (DAFB) in the field peaked at 9 A.M. at 17.2, μmol CO2 m-2 s-1, and then decreased gradually, probably due to the increase in leaf temperature and the decrease of relative humidity. The net photosynthetic rate in leaves on spurs with fruit on fruiting trees was higher than the rate in leaves on spurs without fruit on fruiting trees and non-fruiting trees. Chlorophyll concentration in spur leaves with fruit on fruiting trees was also higher than that in spur leaves without fruit on fruiting trees. Therefore, the effect of fruiting in cherry trees may appear locally rather than wholly in the trees. The net photosynthetic rate in the current shoot leaves was higher than that in the spur leaves. 13C-photosynthates in both current shoot and spur leaves tended to translocate abundantly closer to the fruit from 13C-fed leaves. Whereas when all leaves were defoliated except for 13C-fed leaves, 13C-photosynthates were translocated almost uniformly to each fruit irrespective of the fruiting position because the source for each fruit was limited by the defoliation.

Electrophoresis of leaf and seed proteins of Englerophytum natalense (fam. Sapotaceae)

Englerophytum natalense is an indigenous South African tree, bearing edible fruits. In view of its potential for domestication, leaf and seed proteins were separated electrophoretically in order to investigate the existence and degree of variation within and between populations in respect of these proteins. This was part of a process to search for genetic markers, enabling desirable traits to be identified at an early stage in the lives of non-fruiting trees. Acid Polyacrylamide Gel Electrophoresis (A-PAGE) was performed, but yielded no results. Sodium Dodecyl Polyacrylamide Gel Electrophoresis (SDS-PAGE) was successful, both when using leaves of different ages, and when using seeds. A number of variables in the technique were investigated and compared, and optimum parameters are documented. The gels were analysed with the AlphaEaseTMv 3.3 computer package. The densitometric diagrams showed no variation within or between populations; suggesting that either the species is genetically very uniform, or that the proteins investigated do not constitute suitable markers for variation in this species.

295 The Effect of Cultivar, GA4+7, and Number of Fruit per Spur on Flower Initiation in Apple

Experiments were initiated to document the effect of cultivar, GA4+7, and number of fruit/spur on appendage number and flower bud initiation in apple. `Pacific Rose' is strongly biennial, `Braeburn' and `Fuji' are moderately biennial, and `Royal Gala' is not biennial. In the cultivar study, buds were sampled every 18 days starting at 50 days after full bloom and continuing through until leaf fall to determine the rate of appendage formation and appendage number in relation to doming. Because of the tendency for `Pacific Rose' to exhibit biennial bearing, the rate of appendage formation and the timing of doming were compared on nonfruiting trees, trees carrying a commercial crop, and trees sprayed with 300 PPM GA4+7 applied 14 days after full bloom. Number of appendages for the treatments were similar up to 100 days after full bloom. Presence of fruit on a spur has been demonstrated to inhibit flowering of apple. Spurs of `Pacific Rose', `Splendor', and `Royal Gala' were labeled with zero, one, two, and three fruit per spur and sampled three times during the season. As buds were harvested to count appendage number, the number of fruit per spur and the number of total seeds per spur were recorded. Correlation between number of seeds per spur and rate of appendage formation were done.

A Survey of Tree Planting Practices in the Smallholder Farming Sector of Zimbabwe

SYNOPSIS Group meetings and individual farm visits were used to establish current tree planting practices in the smallholder farming sector of Zimbabwe. The number of tree species planted in each of the eight districts studied ranged from nine to 27 with 17 species occurring in at least half of the districts. Twelve and five of the 17 species were fruit and non-fruit trees respectively and four were indigenous. Paw paw, mulberry, lemon and orange trees were planted in all districts while naartjie, cockwood (Commiphora mollis) and lucky bean tree (Erythina abyssinica) were cultivated in four districts only. With respect to prevalence, paw paw, mangoes, eucalypts, mulberry, lemon, rubber hedge (Euphorbia tirucali) and peach were the most frequent while marula (Sclerocarya birrea), naartjie, cockwood and lucky bean tree were the least frequent. Viewed within a natural region context, tree cultivation was more prevalent in the higher than in the lower rainfall districts. The provision of fruits, poles, fuelwo...

Fruit Finding by Mangabeys ( Lophocebus albigena ): Are Monitoring of Fig Trees and Use of Sympatric Frugivore Calls Possible Strategies?

Frugivorous forest primates face a continual challenge to locate ripe fruit due to the poor visibility characterizing a heavily vegetated habitat and the spatial and temporal unpredictability of their fruit sources. We present two hypotheses regarding fruit finding in gray-cheeked mangabeys (Lophocebus albigena). The first hypothesis is that mangabeys monitor nonfruiting fig trees by visiting and checking them for fruit at a higher rate than control trees that do not produce preferred fruit. We test this hypothesis by comparing rates of visitation to focal fig trees and control trees. The second hypothesis is that mangabeys use sympatric frugivore loud calls to locate fruit sources. We test this hypothesis (1) observationally, by comparing the rates at which mangabeys visit calling sites of sympatric frugivores and matched control areas; and (2) experimentally, by following mangabey responses to playbacks of tape-recorded calls: the black-and-white-casqued hornbill (Bycanistes subcylindricus) long call, the great blue turaco (Corythaeola cristata) rattling kok, the adult male mangabey whoopgobble, and the chimpanzee (Pan troglodytes) pant hoot. We tested the hypotheses via data from a single group of mangabeys in the Kibale National Park, Uganda. There is no evidence that mangabeys monitor fig trees for the presence of fruit, but they may use the calls of hornbills to locate fruit. Statistical evidence that mangabeys use conspecific whoopgobbles and chimpanzee pant hoots in fruit finding is lacking, though anecdotal observations suggest this possibility. There is no evidence for use of turaco calls in fruit finding.

Structural analysis of female and Hermaphroditic Flowers of a Gynodioecious Tree, Ocotea Tenera (Lauraceae)

The evolution of gynodioecy from hermaphroditism involves modifications of floral structure such that male or female fitness is enhanced in hermaphrodites and females, respectively. We present an analysis of structural specialization of flowers of Ocotea tenera, in order to evaluate gender system evolution in this tropical tree species. Significant morphological and anatomical variation was found between high fruiting and low or nonfruiting trees. Female flowers were significantly smaller than hermaphroditic flowers, produced no viable pollen, and made relatively greater allocation to structures that increase female fitness. Hermaphroditic flowers were significantly larger than female flowers, produced copious quantities of pollen, and made relatively greater allocation to male structures. Analyses indicated that changes in allometries between whole-flower growth and growth of reproductive structures may have occurred, which enhance function of the flower and plant as a male or female. Efficiency of nutrient allocation for reproduction is argued to be a factor driving gender system evolution in Ocotea tenera.

Effect of fruiting and drought or flooding on carbon balance of apple trees

The response of fruiting or deblossomed trees to water stress such as drought or flooding was investigated in six semi open-top cuvettes each containing one apple (Malus domestica Borkh. cv. Golden Delicious) tree. Xylem water potentials of leaves dropped from -1.2 to -4.1 MPa within 7 d of drought, the effect being enhanced by fruiting. Apple trees without fruits showed smaller reductions in net photosynthetic rate (P N ) and dark respiration rate (R D ) after 2 d of drought and hence more positive carbon balances relative to fruiting trees. Flooding for 4 d had a more pronounced effect on P N than on transpiration, resulting in a reduced water use efficiency (WUE). This reduction in WUE was greater in the non-fruiting trees. Flooding reduced P N of the whole apple canopies irrespective of fruiting; aple trees without fruits increased R D resulting in a less positive carbon balance relative to fruiting trees. Fruiting increased the sensitivity to drought of apple trees (R D and P N ), but decreased their sensitivity to flooding (R D and WUE), suggesting different adaptation mechanisms for the two forms of water stress.

Changes of Starch and Sorbitol in Leaves Before and After Removal of Fruits from Peach Trees

Changes in contents of nonstructural carbohydrates in leaves, as well as some characteristics of leaves before and after fruit removal, were investigated in potted peach ( Prunus persica L.) trees. Leaf area and dry mass per unit leaf area (SLW) at the fruit-maturation stage decreased with increasing numbers of peaches per tree, whereas the chlorophyll content per unit area in leaves of fruiting trees increased. The chlorophyll content decreased more rapidly upon removal of fruit than that in leaves of fruiting trees. The starch content per unit dry mass in leaves of fruiting trees at the fruit-maturation stage was lower than that in leaves of non-fruiting trees. Starch accumulated significantly in leaves within 1 d of removal of fruit during the fruit-maturation stage and continued to increase thereafter. The accumulation of starch after removal of fruit occurred more rapidly than the decrease in chlorophyll content. Reducing and non-reducing sugars (total sugars) per unit dry mass in the leaves were higher in fruiting trees than in non-fruiting trees. After fruit removal, the total sugar content of leaves increased temporarily and then gradually decreased. The sorbitol content per unit fresh mass in leaves of fruiting trees during the fruit-maturation stage was slightly higher than that in leaves of non-fruiting trees. One day after removal of fruit, the sorbitol content increased in parallel with the accumulation of starch and remained high. The sucrose content of leaves did not change markedly upon removal of fruit.

Household tree holdings: A case study in Mutoko communal area, Zimbabwe

Tree holdings at homesteads and in homefields were investigated for two villages in Zimbabwe. Of the households, 90% owned at least one exotic tree. Trees were concentrated at homesteads and conserved indigenous trees tended to be edible fruit trees. Female heads of households (divorcees and widows) had fewer trees than households headed by men. Households with longer period of residence at a site had increased the proportion of indigenous fruit trees compared to non-fruit trees. Wealth status showed no relationship to tree holdings. The considerable tree planting and tree conservation activity around homesteads and in homefields has the effect of replacing non-fruit indigenous trees with exotic and indigenous fruit trees. Agroforestry research, extension and development should focus more on current practices, concentrate more on trees that farmers favour (such as fruit trees) and take into account differences among households.

Changes in Dormancy and Sensitivity to Vernalization in Axillary Buds of Satsuma Mandarin Examined in vitro During the Annual Cycle

Effect of season and the presence of fruit on bud-endodormancy and the flowering response to low temperature treatments were determined using bud cultures of Owari satsuma mandarin ( Citrus unshiu Marc). Bud dormancy was deeper in fruiting as compared to defruited trees. In fruiting trees, the intensity of bud dormancy was highest in spring, decreased to a low value by early Jul. and then increased until early winter. This increase in dormancy during summer and early autumn did not occur in non-fruiting trees. No flowers formed in buds cultured between May and Sep. Both in fruiting and defruited trees, buds became competent to show a vernalization response to chilling by the end of Oct., at the time they also became capable of sprouting in vitro at low temperature (15/10 °C). There was a direct effect of fruit on the buds which persisted long after fruit removal and resulted in a reduction of the flowering response to chilling.

Effect of Fruiting on Net CO2 Assimilation Rates of Peach and Nectarine Trees

Growth of peach fruits is characterized by a double-sigmoid curve; two periods of rapid enlargement (stages I and III) separated by a lag phase (stage II). Seasonal net CO2 assimilation rates (NAR) were compared in leaves from fruiting and non-fruiting (deblossomed) trees of `Harrow Diamond' (early), and `Vivid' (mid-summer) peach (Prunus persica L. Batsch.) and `Fantasia' (late) nectarine (P. persica) to determine 1) the influence of fruits on photosynthesis and 2) the relationship between NAR and fruit growth. Seasonal trends in NAR tended to be qualitatively similar among the three cultivars, despite genotypic and phenotypic differences. There was a distinct increase in NAR at the time of horticultural fruit maturity (stage III) of each cultivar. Shortly after harvest, NAR rates declined. The average seasonal NAR of fruiting `Harrow Diamond', `Vivid', and `Fantasia' trees was 9%, 11%, and 10% higher, respectively, than that of corresponding non-fruiting trees. Parallel data for total chlorophyll was 28%, 20%, and 19% higher, and specific leaf weight (SLW) was 3%, 5%, and 6% lower, respectively. A negative correlation between NAR and SLW may indicate a feedback inhibition of photosynthesis.

Assessment of Nitrogen Uptake Capacity in Mature Alternate-bearing Pistachio (Pistacia vera) Trees

The interrelationships between crop load, root growth, and nutrient uptake in mature, pistachio trees were examined in this study. Nutrient uptake was determined during the spring, summer, and fall using labeled nitrogen (15N) and boron (10B) and by differences in whole-tree accumulation between tree harvests for other nutrients (e.g., P, K, Ca, Zn). Nitrogen and boron uptake were double in fruiting compared with nonfruiting trees in the spring. Most of the labeled N was found in the developing fruits and leaves. Total labeled N recovery during the spring flush period, however, was low, indicating that much of the N in the fruit came from N reserves from within the tree rather than uptake from the soil. In contrast, significant amounts of N were taken up from the soil during the summer uptake period. Thus, our data support the hypothesis that sink demand (i.e., fruit development) conditions N uptake in pistachio. The relationship between root growth and N uptake was also examined in this study. Root observation chambers were constructed, and root growth determined by tracing roots growing up against the glass windows. Root length, root growth rate, relative root growth rate, and total tree fine root weight were all greater in nonfruiting compared to fruiting trees during the fruit development period (late May to mid-July). Surprisingly, fruiting trees had less root growth, but greater N uptake than nonfruiting trees during this period. This evidence suggests that N uptake is decoupled from root growth in mature pistachio trees.

Water use by European pear trees growing in drainage lysimeters

SummaryResults are discussed of a four-year study on water use by European pear trees, of cvs Conference and Comice on slender spindle and V-trellis training systems, growing outdoors in drainage lysimeters. The study covered the period from planting until the end of the first cropping season. During the first half of each season, weekly water use increased in relation to estimated potential evapotranspiration, presumably as the evaporative leaf surface area increased. In the final year, when the tree leaf area was up to 2 m2 m−2 planting square area, weekly water use was always less than 40% of the potential evapotranspiration. Annual water use varied strongly with variety and training system. For non-fruiting trees however, annual water use per unit leaf area at the end of the season showed a consistent relationship for trees of all variety x training system combinations. In the final year, the presence of fruit generally increased water use, especially per unit leaf area or per unit root weight.

Carbon Exchange Rate and Accumulation in Limbs of Fruiting and Nonfruiting Apple Trees

Mature `Sturdeespur Delicious' apple (Malus domestica Borkh.) trees on MM.106 rootstocks were hand-deblossomed or hand-pollinated in 1989 and 1990. Two representative limbs were chosen at bloom on each tree in 1989, one of which was girdled (G) while the other served as a control. One representative limb was selected at bloom in 1990. Three leaf types were studied: shoot (SH) leaves, leaves on nonfruiting (NF) spurs (S-F), and leaves on fruiting (F) spurs (S + F). The presence of fruit did not affect C exchange rate (CER). Girdling fruiting limbs reduced CER by ≈10%. Girdling NF limbs resulted in starch accumulation in the leaves and low CER. SH leaves had the highest CER per unit leaf area, while S + F leaves had the lowest. Total seasonal dry weight (DW) accumulated in leaves, fruit, and wood, normalized per square centimeter limb cross-sectional area (LCSA), was higher in F trees. Roots were longer and DW of roots extracted from soil core samples was higher in NF trees. NF trees had significantly more vegetative growth in new shoots and dry-matter increment in wood than F trees.

Respiration rate and ethylene production in inflorescence buds of pistachio in relation to alternate bearing

Respiration rate and ethylene production were measured in inflorescence buds and the surrounding tissue on fruiting and non-fruiting trees of pistachio ( Pistacia vera cultivar ‘Aegenes’). The buds from fruiting trees had higher respiration rates than non-fruiting ones, before and during the abscission period. In contrast, the ethylene production in buds was not significantly different between fruiting and non-fruiting trees. The results indicate that in inflorescence buds, an increased respiration preceded their abscission, and that endogenous ethylene production is not related to bud abscission in pistachio.

Net photosynthesis, stomatal conductance, chlorophyll content and specific leaf weight of pistachio trees (cv. Aegenes) as influenced by fruiting

SUMMARYNet photosynthesis (Pn), stomatal conductance (gs) and chlorophyll content (chl) were measured on fruiting and nonfruiting pistachio trees (Pistacia vera cv. Aegenes) in 1991 and 1992. Specific leaf weight (SLW) was also measured in 1992. Measurements were taken at frequent intervals from May to September in 1991 and from April to August in 1992. Pn, gs and chl in fruiting trees were greater than in nonfruiting ones from the begin-ing of measurement until mid-June in both years. From mid-June onwards, Pn and gs started to decrease slightly but were approximately the same in fruiting and nonfruiting trees. Chlorophyll (a/b) was similar for fruiting and nonfruiting trees throughout the period of measurement. Although no significant differences were found in SLW between leaves of fruiting and nonfruiting trees, SLW was higher in fruiting than nonfruiting trees until the end of May, after which this relationship was reversed. The results showed that fruiting affected chl, gs and Pn rates from early in the season until mid-June, the period which precedes the onset of bud abscission and seed growth.

Morphological Differences among Apple Leaf Types

Leaf characteristics of mature `Sturdeespur Delicious'/MM.106 apple trees (Malus domestica Borkh.) were studied in two experiments. In 1989 canopy foliage on fruiting trees was divided into shoot leaves, leaves on nonfruiting spurs, and leaves on fruiting spurs. Shoot leaves were the heaviest, the largest, and contained the highest internal gas volume and chlorophyll content. The two spur-leaf types differed in their leaf characteristics except for stomate density. In 1990 shoot and spur leaves on nonfruiting spurs on fruiting trees had lower leaf water content than those leaves on nonfruiting trees. All other shoot-leaf characteristics were similar. Leaves on nonfruiting spurs on nonfruiting trees were larger than those on fruiting trees.

Partitioning of Above-ground Dry Matter in `Lambert' Sweet Cherry Trees With or Without Fruit

The effect of fruit on shoot growth, leaf area, and on dry weight (DW) partitioning into leaves, fruit, trunk, and branch sections was investigated using 7-year-old `Lambert' sweet cherry (Prunus avium L.) trees. Dormant trees were sampled in the spring, and fruiting and deblossomed trees were sampled and compared at fruit harvest and just before leaf fall. Fruiting reduced shoot growth, leaf area, and above-ground DW accumulation of the trees. The annual above-ground DW accumulated was 13.4 kg for fruiting trees and 16.0 kg for nonfruiting trees. The greatest proportion of above-ground DW was partitioned to wood, whereas the least was partitioned to fruit. Current-season's growth (wood and leaves) appears to be a greater sink for photosynthates than is fruit because a greater proportion of above-ground DW was partitioned to current-season's growth than to fruit.