The comparative tissues were 30 opposite cluster petioles, 30 2-inch shoot tips and 15 flower clusters per plot. The flower clusters were separated into the cluster stem framework and the individual unopened flowers . While the trial area was of low boron status, the presence of borondeficiency symptoms in fruit was not extensive enough to compare the treatments for visual evaluation or yield response. Boron levels were significantly increased by the spray treatment in all of the sampled tissues , including tissues receiving the direct spray , as well as the new shoot-tip growth that was not yet present at the time of spraying. Care was taken to sample only actively growing shoot tips that had grown beyond the spray deposit. Representative shoot tips were marked with a black felt pen at the time of treatment, in order to measure subsequent new growth. Therefore, boron would have been translocated into the growing shoot tip from the sprayed tissues below. These results suggested that there is some phloem mobility of boron, and that foliar sprays have the potential to prevent boron deficiency of shoots in a timely manner during the growing season. A follow-up study was conducted in the same vineyard during 1999, in an area observed in 1998 to be severely boron deficient. We compared the effects of boron timing and spray type on fruit-set and development as well as on vine tissue concentrations. There were five treatments: control ; fall foliar, Oct. 19, 1998; dormant soil berm spray, Feb. 8, 1999; pre-bloom foliar, May 4, 1999; and bloom foliar , May 20, 1999.
All treatments were applied at 1-pound boron per acre as 20.5% boron soluble product. The foliar sprays were applied at 150 gallons per acre, round nursery pots and the berm soil spray was applied at 30 gallons per acre . The trial design was five-vine plots, replicated five times in a randomized block design. The following samples were collected: dormant canes in treatments 1and 2 to determine boron uptake from the fall foliar spray, Feb. 26, 1998; early bloom , May 17, 1999, in all treatments; and veraison , July 15, 1999, in all treatments. Thirty samples of each tissue type were collected from each plot. The cane samples consisted of one-node sections . The buds were excised and analyzed separately. All tissue samples were triple-rinsed in distilled water, oven-dried and analyzed for boron at the ANR Analytical Laboratory at UC Davis. Fruit response was determined by visually grading all individual clusters in each plot for the presence of boron defi- ciency symptoms on Aug. 15, 1999. Each cluster was scored as the percentage of the cluster showing combined symptoms of reduced fruit-set and the presence of the pumpkin-shaped shot berries characteristic of boron deficiency. All of the data was subjected to ANOVA. When treatment effects were significant , treatment means were separated by Duncan’s new multiple range test.The fall foliar treatment significantly increased boron levels in the dormant bud tissues, but the cane tissues were not affected . At bloom, the prebloom foliar treatment had the highest boron concentrations of all sampled tissues. The fall foliar treatment also increased bloom tissue boron levels, but not as much as the pre-bloom foliar treatment. The bloom treatment had not yet been sprayed at the time of tissue sampling and so was similar to the control. The dormant soil treatment didnot increase boron in the sampled tissues by bloom.
At veraison, all of the foliar spray treatments increased shoot-tip boron levels. The dormant soil treatment was intermediate among the treatments in shoot-tip boron concentration and was not different from either the control or the three foliar treatments. This 1999 study confirmed the 1998 pre-bloom spray treatment results by showing that boron concentrations increased in all of the sprayed tissues, as well as in new shoot tips thereafter.Evidence of phytotoxicity after treatment was noted with the pre-bloom and bloom foliar sprays, but not with the fall foliar or the dormant soil berm sprays. Young, expanding leaves showed some necrosis and cupping at their margins. This demonstrated that spring and summer spray treatments should be used at a lower rate than the 1 pound of boron per acre used in our trial; one-half pound of boron per acre spray treatments have been shown to be safe at these times.Boron deficiency in fruit was reported as incidence and severity . The incidence of boron defi- ciency in the control was 78% . Likewise, the fall foliar treatment had the lowest severity of boron-deficiency symptoms in fruit . The other boron treatments also reduced fruit symptom severity, but not as effectively as the fall foliar treatment. Vine fruit response did not correspond directly with tissue boron levels. While fruit symptoms were reduced more effectively by the fall foliar than the pre-bloom foliar treatment, tissue boron levels were higher in the latter than in the former treatment. This may be due to the inability of the pre-bloom foliar spray to reverse some earlier effects of boron deficiency on primordial tissue in developing buds. Also, at pre-bloom, the calyptrae prevent the foliar spray from contacting the unexposed flower parts . These calyptrae are shed at bloom, along with their spray deposits, finally exposing the flower parts to complete their pollination and fruit-set.
Boron has long been recognized as being immobile or only slightly mobile in the phloem of many plant species . However, boron is highly mobile in the phloem of certain plants, including pome fruits, stone fruits and nut tree crops of Malus, Prunus and Pyrus spp., respectively . This boron mobility is due to the production of sugar alcohols, enabling the cotransport of boron-polyol complexes in the phloem . Such plants accumulate boron in their apical tissues and exhibit boron toxicity as shoot-tip dieback. Tree crops that have responded well to foliar boron sprays at pre-bloom, bloom and/or fall include almonds , cherries , pears and prunes . All of these trees have been demonstrated to Fig. 1. Effects of boron soil and foliar spray treatment on incidence and severity in a Thompson Seedless grape vineyard, Kingsburg, 1999. Treatment means with different letters are significantly different according to Duncan’s new multiple range test, P ≤ 0.05. be phloem-mobile for boron. Fall foliar boron sprays have sometimes shown superior improvements in both fruit-set and yields in prunes and almonds as compared to spring sprays . The mobility of boron in grapevine tissues is not well understood. Scott and Schrader found that boron concentrations in mature grape leaves declined when boron was absent from the root environment, suggesting remobilization of boron from leaves. Remobilization of boron is its movement from one organ to supply another organ or tissue in the plant. Brown and Hu found native, wild grapevines to be intermediate in phloem boron mobility when compared to other woody plants. Nonmobile plants always accumulate boron in the edges of older leaves , a characteristic of the European grape Vitis vinifera . Also,grapevines are susceptible to temporary boron deficiency of developing tissues during periods of drought, plastic flower pots suggesting limited boron mobility. Therefore, Vitis spp. do not appear to show the same characteristics of boron mobility and accumulation as the phloem-mobile tree crops of Malus, Prunus and Pyrus spp. In this study, some limitations in phloem boron mobility of grapevines may explain our finding that the pre-bloom boron spray was less effective at reducing fruit symptoms than the fall spray. Pre-bloom-applied boron may not have been sufficiently translocated into the flower parts by bloom to prevent some fruit symptom development. Conversely, fall-applied boron may have been incorporated into floral parts early enough to prevent most deficiency effects at bloom. The bloom spray tended to be intermediate between the pre-bloom and fall sprays in fruit response. At bloom, the calyptrae are shed, exposing the floral parts, including pollen, to a direct foliar spray. This direct contact with boron may have enhanced fruit-set as compared to the pre-bloom spray.Our results indicate that fall foliar treatment may be the best insurance against boron-deficient inflorescence tissues at bloom. While pre-bloom and bloom foliar treatments can also reduce boron-deficiency symptoms in fruit, growers should consider an earlier treatment in the fall because it may be more effective. Foliar spraying can also be used to correct vegetative boron-deficiency symptoms, as indicated by increased boron concentrations in shoot tips after spraying. The soil treatment in this study was only partially effective in correcting the boron deficiency. However, only 1 pound of actual boron was applied per acre, whereas 4 to 5 pounds boron per acre are normally recommended as an initial soil treatment under furrow irrigation. The 1-pound rate was used in all treatments in this trial to make a direct comparison of treatment method only. Foliar boron spraying can be used as a temporary or emergency treatment, or as a method of vineyard maintenance. With annual treatment, there should ultimately be enough residual boron in the soil to provide for more constant uptake and long-term correction of the deficiency. Spring and summer applications of boron should not exceed 0.5 pound per acre for each spray to avoid phytotoxicity. Mild necrosis at the margins of immature leaves can occur at rates exceeding 0.6 to 0.8 pounds boron per acre.
The annual recommended rate of 1-pound boron per acre can be safely achieved by applying two sprays of 0.5 pound each. However, vine foliage is more tolerant of boron after harvest in the fall, safely receiving up to 1 pound per acre in a single application. Most soluble boron products are derived from sodium borates, resulting in well-buffered, alkaline solutions of pH 8.6 to 8.7. If the boron is to be combined with a product that is susceptible to alkaline hydrolysis, then it will be necessary to reduce the pH with an acidifier such as citric acid. After initial foliar spray treatment, growers may wish to switch to another method of boron application for maintenance, such as fertigation with drip irrigation . The choice of application method can be based on equipment availability and convenience while using the same fertilizer product. Growers should also routinely monitor boron treatments with leaf petiole or blade analysis, due to the narrow margin between boron deficiency and toxicity.Habitat complexity is critical for the functioning of ecological communities in both terrestrial and aquatic systems. Processes such as resource foraging, colonization, and species interactions often depend on the level of heterogeneity in the configuration of physical elements in a habitat . Vegetation connectivity and structure are important components of habitat complexity and can influence species interactions and community patterns at local scales. In aquaticsystems, more complex habitats made up of macrophytes support communities that are more diverse and abundant, and allow for greater food capture than systems without vegetation . In terrestrial systems, vegetation structure—such as the biomass of foliage and the variety of plant architectures—generally influences species composition, and increases species richness and abundance of numerous taxa . Additionally, vegetation structure can influence mobility and foraging success of vertebrates and invertebrates . In tropical ecosystems, ants are among the most abundant and biodiverse of taxonomic groups and are considered important predators, herbivores, and seed dispersers . Ants are cursorial central-place foragers—organisms that forage from a central place to which they return with food to feed with the colony . Therefore, foraging and discovery of food resources is strongly constrained by the need to construct and follow trails along vegetation . This is particularly relevant for ants using the arboreal stratum as their primary foraging space . For instance, the availability of vegetation connections can maximize ants’ foraging efficiency, locomotion, and velocity , as well as contribute to changes in community composition and species richness . The availability of such resources can ultimately lead to differences in resource utilization by ant communities . In tropical agricultural systems, especially agroforests, ants play important ecological roles , and management practices can strongly influence ant behavior and their potential for providing biological pest control services . Indeed, one of the oldest known records of the use of ants for pest control dates to 304 A.D in citrus plantations in China. In these systems, artificial connections made of bamboo were used by farmers to facilitate foraging by the Weaver Ant to suppress damaging phytophagous insects.