Fruit trees in orchards of the mid-Atlantic region of the United States are often planted in vegetation-free rows alternating with grass alleys. Grass managed to suppress weeds but to compete ...minimally with fruit trees may be an alternative to herbicide and tillage. This research was conducted in the greenhouse and field to assess five different grasses that may suppress weeds without reducing yield of fruit trees. In the greenhouse with high seeding rates, red fescue competed more effectively than did chewings fescue, tall fescue, and perennial ryegrass with three weeds (damesrocket, cornflower, and chicory). However, with reduced seeding rates, similar to rates used in the field, grass competitiveness with weeds was similar between red fescue, tall fescue, and perennial ryegrass. Similar results were obtained during a 4-yr field experiment; roughstalk bluegrass competed least effectively with weeds but the other four grasses provided similar weed suppression—generally providing as much weed suppression as traditional herbicides. None of the candidate grasses significantly reduced yields of 10-yr-old apple and peach trees, although fruit size was affected by some grasses. The grass that was least suppressive of yield, roughstalk bluegrass, was the least effective in controlling weeds. Annual mowing in combination with four of the grasses tested is one option to manage the orchard floor with reduced herbicides, but fruit size may decrease. Nomenclature: Chicory, Cichorium intybus L.; cornflower, Centaurea cyanus L.; damesrocket, Hesperis matronalis L.; apple, Malus × domestica Borkh.; chewings red fescue, Festuca rubra var. commutata L. Gaudin; peach, Prunus persica (L.) Batch; perennial ryegrass, Lolium perenne L.; red fescue, Festuca rubra L.; roughstalk bluegrass, Poa trivialis L.; tall fescue, Lolium arundinaceum (Schreb.) S.J. Darbyshire.
Laboratory and greenhouse experiments were conducted to determine the herbicidal effect of plant-derived oils and to identify the active ingredient in an oil with herbicide activity. Twenty-five ...different oils were applied to detached leaves of dandelion in the laboratory. Essential oils (1%, v/v) from red thyme, summer savory, cinnamon, and clove were the most phytotoxic and caused electrolyte leakage resulting in cell death. Each of these essential oils in aqueous concentrations from 5 to 10% (v/v) plus two adjuvants (nonionic surfactant and paraffinic oil blend at 0.2% v/v) were applied to shoots of common lambsquarters, common ragweed, and johnsongrass in the greenhouse; shoot death occurred within 1 h to 1 d after application. Essential oil of cinnamon had high herbicidal activity, and eugenol (2-methoxy-4-2-propenylphenol) was determined to be this oil's major component (84%, v/v). Dandelion leaf disk and whole-plant assays verified that eugenol was the active ingredient in the essential oil of cinnamon. Essential oils are extracted from plants and thus may be useful as “natural product herbicides” for organic farming systems.
Apple rootstock resistance to drought Tworkoski, Thomas; Gennaro Fazio; D. Michael Glenn
Scientia horticulturae,
06/2016, Letnik:
204
Journal Article
Recenzirano
Odprti dostop
Water for irrigation will likely be less available in apple-growing regions due to climate change and competition with human needs other than agriculture. Apple cultivars and rootstocks may differ in ...water use necessary for acceptable cropping. In two greenhouse experiments in 2014 and 2015 rootstocks (M.9 and MM.111) and scions (âGalaâ and âFujiâ) with known differences in size control and potential resistance to drought were compared under conditions of reduced water availability. After 1 week without irrigation in 2014 the potting soil moisture and leaf water potential (ΨL) were reduced more in trees on MM.111 than M.9 rootstocks and by âGalaâ than âFujiâ scions. Abscisic acid (ABA) and associated metabolites dihydrophaseic acid, abscisic acid glucose ester, and phaseic acid generally were greater for both scions on M.9 than MM.111. Concentrations of ABA metabolites were greater in âGalaâ than âFujiâ suggesting significant metabolic rates in leaves. As noon ΨL decreased between â1.5 and â2.0MPa leaf ABA levels increased exponentially to concentrations above 500ng/g dw and stomatal conductance (gs) decreased to less than 50 mmole H2O mâ2sâ1. At reduced gs carbon assimilation (A) was low but greater in trees on M.9 than on MM.111. Trees grown on M.9 partitioned less dry weight (dw) to roots than MM.111. However the% dw partitioned to fine roots was greater in M.9 than MM.111 which may have helped trees grow in a small environment such as a pot. In 2015 trees were grown in 45- and 75-L pots and irrigated over 3 weeks to maintain a steady ΨL between â1.5 and â2.5MPa. This longer-term water stress in 2015 resulted in greater gs and A in trees on MM.111 and in larger pots but WUE was still greater in trees grafted to M.9 in 3 of the 5 drought dates measured. Both rootstocks provided drought resistance, but by mechanisms which appear to differ and which may provide benefits to apple trees grown with reduced irrigation or with water stress. The dwarfing rootstock M.9 produces higher levels of ABA that may regulate stomatal opening and improve short-term drought resistance. The more invigorating rootstock MM.111 may be drought hardy in the longer-term due to development of a more extensive root system.
Laboratory and greenhouse experiments were conducted to determine the herbicidal effect of plant-derived oils and to identify the active ingredient in an oil with herbicide activity. Twenty-five ...different oils were applied to detached leaves of dandelion in the laboratory. Essential oils (1%, v/v) from red thyme, summer savory, cinnamon, and clove were the most phytotoxic and caused electrolyte leakage resulting in cell death. Each of these essential oils in aqueous concentrations from 5 to 10% (v/v) plus two adjuvants (nonionic surfactant and paraffinic oil blend at 0.2% v/v) were applied to shoots of common lambsquarters, common ragweed, and johnsongrass in the greenhouse; shoot death occurred within 1 h to 1 d after application. Essential oil of cinnamon had high herbicidal activity, and eugenol (2-methoxy-4-2-propenylphenol) was determined to be this oil's major component (84%, v/v). Dandelion leaf disk and whole-plant assays verified that eugenol was the active ingredient in the essential oil of cinnamon. Essential oils are extracted from plants and thus may be useful as “natural product herbicides” for organic farming systems. Nomenclature: Cinnamon, Cinnamomum zeylanicum; clove, Syzgium aromaticum; red thyme, Thymus vulgaris; summer savory, Satureja hortensis; common lambsquarters, Chenopodium album L. CHEAL; common ragweed, Ambrosia artemisiifolia L. AMBEL; dandelion, Taraxacum officinale Weber in Wiggers TAROF; johnsongrass, Sorghum halepense (L.) Pers. SORHA.
Branch orientation and distribution determine tree architecture that can influence orchard design and management. Peach
Prunus persica
L. (Batch) trees with three different branching genotypes were ...evaluated: fewer, nearly vertical branches (pillar), less vertical and more spreading branches (upright), and more abundant, least vertical branches (standard). Auxin concentrations and expression of genes that regulate branch development in herbaceous species,
MAX1
,
2
,
3
,
4
and
TAC1
were determined. Shoots and roots of peach trees in the field and greenhouse were studied following pruning and during periods of growth when bud break and branch spatial orientation develop. Expression of
MAX3
and
MAX4
decreased in stems of field-grown peach trees that remained on the tree following pruning. In the greenhouse elevated auxin concentrations and higher gene expression of
MAX3
in roots and
MAX4
in stems were found in pillar rather than standard trees. Upright trees had auxin and
MAX1
–
4
expression that was intermediate between pillar and standard trees. Temporal differences were found with
MAX1
–
4
expression being greater in April or May but auxin concentrations were greater only in shoots in May. Expression of
TAC1
was inversely related with auxin concentrations in shoots and was greatest in standard and least in pillar trees. The current work indicates that in stems, auxin,
MAX3
–
4
genes, and
TAC1
genes may influence regulatory processes that affect growth and development of peach trees with different growth habits. In addition to breeding, new plant growth regulators that affect the modes of action of root-originating signals may provide new cultural tools for managing tree growth and development.
The effect of high temperature and oxidative stress on the cell viability of the yeast antagonist, Metschnikowia fructicola was determined. A mild heat shock (HS) pretreatment (30 min at 40 °C) ...improved the tolerance of M. fructicola to subsequent high temperature (45 °C, 20-30 min) and oxidative stress (0.4 mol L⁻¹ hydrogen peroxide, 20-60 min). HS-treated yeast cells showed less accumulation of reactive oxygen species (ROS) than nontreated cells in response to both stresses. Additionally, HS-treated yeast exhibited significantly greater (P<0.0001) biocontrol activity against Penicillium expansum and a significantly faster (P<0.0001) growth rate in wounds of apple fruits stored at 25 °C compared with the performance of untreated yeast cells. Transcription of a trehalose-6-phosphate synthase gene (TPS1) was upregulated in response to HS and trehalose content also increased. Results indicate that the higher levels of trehalose induced by the HS may contribute to an improvement in ROS scavenging, stress tolerance, population growth in apple wounds and biocontrol activity of M. fructicola.
Ground covers and irrigation are important components of orchard floor management systems that affect fruit tree vigor and productivity. Three experiments were conducted in a greenhouse to determine ...the relative water use of candidate ground covers (roughstalk bluegrass, RB, Poa trivialis), Chewing's fescue (CH, Festuca rubra subsp. commutata Gaudin), creeping red fescue (RF, Festuca rubra L. subsp. rubra), tall fescue (TF, Festuca arundinacea Schreber, Fawn), and perennial ryegrass (PR, Lolium perenne L., 'Saint') and the response of apple trees to those ground covers and to drip irrigation applied at two soilless substrate depths. Grass ground covers with large and deep root systems (TF and PR) used more water than a shallow- rooted grass (RB) and leaf water potential decreased more rapidly in apple trees grown with TF than RB when irrigation was withheld. Although apple tree shoot growth was greater with shallow- than deep-rooted grass, photosynthesis, transpiration, and root biomass distribution were not differentially affected by grass type. When grown with RB or TF, irrigation depth affected apple tree growth. During the first season in the greenhouse, deep irrigation at 37 cm depth increased apple root length density near emitters but shoot growth was less in apple grown with deep irrigation compared with apple grown with surface irrigation (0 cm) and with split irrigation at 0 and 37 cm. During the second season in the greenhouse, deep irrigation was beneficial to trees grown with grass that had large, deep root systems (TF) but it did not completely overcome interference effects of grass on apple trees, regardless of grass root system size or distribution. The results indicate that grasses with shallow root systems may be grown beneath apple trees and that split irrigation at two depths can provide flexibility that is necessary for water management of ground covers and apple trees.
Plant foraging response is a process in which clonal plants proliferate in nutrient-rich sites by shortening stolon length and increasing ramet density. Conversely, stolon length increases and ramet ...density decreases in nutrient-poor sites. Four genotypes of strawberry (
Fragaria
chiloensis (L.) Duch.) were grown in a greenhouse for 10 weeks and treated with different concentrations of nitrogen. Genotypes differed in plant size, stolon and ramet production, and nitrogen distribution between parent and ramets. Genotype Q18 were the smallest plants with the greatest number of stolons and ramets, typical of the phalanx morphology. The other genotypes had fewer but longer stolons, typical of the guerrilla morphology. Number of stolons and ramet density increased with increased N more in Genotype Q18 than the other genotypes. Results indicate that vegetative growth changed in response to increasing N treatment of the parent plant by shortening the average stolon length, increasing the number of stolons, and increasing the number of ramets while maintaining total stolon length. Foraging response characteristics were observed in strawberry but varied among genotypes.
PDF
