Reductions in weed interference achieved through hand weeding or herbicides in a newly planted peach (Prunus persica (L.) Batsch) orchard led to increased summer growth and greater freezing resistance of bark and wood tissue in dormant scions. Controlled freezing tests for 2 winters following spring plantings indicated that bark and xylem tissues of scions from weed-free plots averaged 5.5° and 3.2°C more cold hardy, respectively, than those from unweeded plots.
An equation for predicting bulk density (BD) of pine bark and sand potting media was devised using BD data from laboratory analysis of individual components. BD values calculated from the predictive equation and actual values obtained from potting medium samples were compared. Actual and predicted BD increased linearly with each incremental increase in percentage sand in the medium. Actual and predicted BD values were not significantly different. The devised equation is applicable to media other than bark and sand.
Paclobutrazol, a triazole growth regulator, effectively regulates pecan vegetative growth when applied as a soil or trunk drench. However, its absorption and subsequent biological activity in leaves and shoot tissue is not well understood. Terminal shoots from scaffolds of 8-yr-old `Chickasaw' pecan trees were treated with paclobutrazol after leaf flush in mid-May of 1988. Treatments included painting a mixture of 10 mg a.i. paclobutrazol and 1 ml distilled water onto either 1-yr-old wood, green wood, or the abaxial leaf surface. Shoot growth measurements and nut counts were taken in October of 1988 and 1989 on the treated shoots and all shoots arising from them. Paclobutrazol significantly increased the number of nuts per shoot in 1988, but did not affect shoot growth. More nuts were found on shoots from the 1-yr-old wood and leaf treatments than from the control and green wood treatments. In 1989, shoot growth was significantly less in the 2 former than the 2 latter treatments. These data indicate that paclobutrazol was absorbed through the bark of 1-yr-old wood and abaxial leaf tissue and sub-sequently translocated to areas of shoot growth.
Tomatoes are the most abundantly produced greenhouse vegetable crop in the United States. The use of compost substrates has increased in recent years for the greenhouse production of many vegetables, bedding plants, and nursery crops. `Blitz' tomatoes were grown during the spring and fall growing seasons in 2004 in six substrate blends of pine bark (PB), a traditional production substrate in the Southeastern U.S., and cotton gin compost (CGC), an agricultural by-product, to assess the potential use of CGC as a viable replacement for PB for the production of greenhouse tomatoes. Treatments ranged from 100% PB to 100% CGC. During both growing seasons, plants grown in substrates containing CGC produced similar total, marketable, and cull yields compared to plants grown in 100% PB. Substrates containing 40% or more CGC had significantly higher EC levels both initially and throughout both growing seasons than did 20% CGC and 100% PB blends. Initial and final pH of all substrates was similar during both studies and remained within recommended ranges for greenhouse tomato production. Water-holding capacity increased as the percent CGC increased in each substrate blend, indicating the need for less irrigation volume for substrates containing CGC compared to the 100% PB control. Results indicate that CGC can be used as an amendment to or replacement for PB in greenhouse tomato production.
In the southeastern United States, inconsistent pine bark (PB) supplies and overabundance of cotton gin by-products warrant investigation about the feasibility of replacing PB with cotton gin compost (CGC) for container horticultural plant production. Most research on the use of composted organic substrates for horticultural plant production has focused on shoot growth responses, so there is a need to document the effect of these substrates on root growth. In 2004, `Blitz' tomato (Lycopersicon esculentum), `Hot Country' lantana (Lantana camara `Hot Country'), and weeping fig (Ficus benjamina) were placed in Horhizotrons to evaluate root growth in 100% PB and three PB:CGC substrates containing, by volume, 60:40 PB:CGC, 40:60 PB:CGC, and 0:100 PB:CGC. Horhizotrons were placed in a greenhouse, and root growth in all substrates was measured for each cultivar. Physical properties (total porosity, water holding capacity, air space, and bulk density) and chemical properties (electrical conductivity and pH) were determined for all substrates. Physical properties of 100% PB were within recommended guidelines and were either within or above recommended ranges for all PB:CGC substrate blends. Chemical properties of all substrates were within or above recommended guidelines. Root growth of all species in substrates containing CGC was similar to or more enhanced than root growth in 100% PB.
Pine bark-filled containers periodically fertilized with a (NH4)2SO4 solution were heated from 21°C to one of 5 temperatures (28°, 34°, 40°, 46°, or 52°C) for a daily exposure duration of 1, 2, 4, 6, or 24 hours. Medium solution extracts were analyzed for NH4-N and NO3-N every 5 days for 20 days. Treatment temperature of at least 40°C and a daily exposure duration of 24 hours was necessary to inhibit nitrification, thereby increasing NH4-N concentration in the medium solution. Similar increase in NH4-N was found for a 2 hr/day exposure to 46°C, with further increases in NH4-N at longer exposure times. By day 10, the maximum level1 of NH4-N concentration in medium extracts was found after a 1 hr/day exposure to 52°C. Decreases in medium solution NO3-N concentration generally coincided with the increases in NH4-N. Results indicate that high container temperatures may increase the ratio of NH4-N to NO3-N in the medium solution of plants fertilized with predominantly ammoniacal N.
Pine bark-filled containers periodically fertilized with NH4-N were heated from 21C to 28, 34, 40, 46, or 52C for daily exposures of 1, 2, 4, 6, or 24 hours over 20 days. Concentrations of NH4-N and NO3-N in medium solution extracts were determined every 5 days. Medium solution NH4-N concentration was higher at constant (24 hours) exposure to 40C than at lower temperatures or exposure times. There was a similar increase in NH4-N concentration for a 2-hour·day–1 exposure to 46C, with further increases in NH4-N for longer exposure times. By day 10, NH4-N concentration was highest after 1 hour·day–1 exposure to 52C. Decreases in medium solution NO3-N concentration generally coincided with the increases in NH4-N. These results indicate that container medium thermal periods, similar to those observed in nurseries of the southern United States, may inhibit nitrification, thereby influencing NH4-N: NO3-N ratios in the medium solution of plants fertilized with predominantly ammoniacal N sources.
Studies with herbaceous crops have indicated a similarity in the types of proteins that accumulate in response to environmental stresses and ABA. Many of these proteins belong to a group called dehydrins. We have identified a 60 kDa dehydrin-related protein (PCA 60) in peach associated with cold hardiness. Our objective was to determine if seasonal induction of dehydrins are a common feature in a wide array of woody plants Bark tissues from eight species of woody plants were collected monthly for 1.5 years. The species included: Prunus persica `Loring'; Malus domestica `Golden Delicious'; Rubus sp. `Chester'; Populus sp.; Salix babylonica; Cornus florida; Sassafras albidum, and Robinia Pseudo-acacia. Protein extraction, SDSPAGE, and immunoblotting were performed as previously reported. Immunoblots were probed with a polyclonal antibody recognizing a conserved region of dehydrin proteins (provided by Timothy Close). Although some proteins, immunologically related to dehydrins, appeared lo be constitutive, distinct seasonal patterns associated with winter acclimation were observed in all species. The molecular weights of these proteins varied, although there were similarities in related species (willow and poplar). Although this study represents a precursory examination of dehydrins, the results indicate that these proteins are common to woody plants and that further research to characterize their function is warranted.
In response to environmental cues plants undergo changes in gene expression that result in the up- or down-regulation of specific genes. To identify genes in peach [Prunus persica (L.) Batsch.] trees whose transcript levels are specifically affected by low temperature (LT) or short day photoperiod (SD), we have created suppression subtractive hybridization (SSH) libraries from bark tissues sampled from trees kept at 5 °C and 25 °C under short day (SD) photoperiod or exposed to a night break (NB) interruption during the dark period of the SD cycle to simulate a long day (LD) photoperiod. Sequences expressed in forward and reverse subtractions using various subtracted combinations of temperature and photoperiod treatments were cloned, sequenced, and identified by BLAST and ClustalW analysis. Low temperature treatment resulted in the up-regulation of a number of cold-responsive and stress-related genes and suppression of genes involved in “housekeeping” functions (e.g., cell division and photosynthesis). Some stress-related genes not observed to be up-regulated under LT were increased in response to SD photoperiod treatments. Comparison of the patterns of expression as a consequence of different temperature and photoperiod treatments allowed us to determine the qualitative contribution of each treatment to the regulation of specific genes.
A high incidence of longitudinal trunk bark cracking was observed in an apple planting with 4 scion cultivars and 9 rootstocks between Nov., 1969 and Feb., 1972. The injury, occurring mostly in late Nov., was related to scion and rootstock. Almost no cracking occurred on ‘Wellspur’ and ‘Red King’ trunks. More cracking occurred on ‘Golden Delicious’ than ‘Goldspur’ on 3 rootstocks. With these 3 rootstocks, 96% cracking occurred with ‘Golden Delicious’/‘M 7’ and ‘MM 106’ and 52% with trees on ‘M 26’. With ‘Goldspur’ on 9 different rootstocks, the highest incidence of cracking was with trees on ‘M 7’ (85%) and ‘MM 106’ (82%) while 30% cracking occurred with trees on domestic seedling, and 4% with trees on ‘M 25’ No cracking was observed with ‘Goldspur’/‘M 26’. The greatest no. of cracks occurred on the S sector of the trunks with moderate amounts on the SE and E sectors with fewer cracks on all other sectors. The cracking appears to be low temp induced and the effect of rootstocks appears to be an effect on fall maturity of the scion.