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.
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.
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.
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.
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.
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.
Gasifier residue (GR) had less than half the vertical shrinkage of pine bark or 2-bark : 1-peat : 1-sand medium. Little change in particle size distribution occurred in gasifier residue or 2-GR : 1-peat : 1-sand medium over 9 months. Particle breakdown occurred in bark, 2-bark : 1-peat : 1-sand and 3-GR : 1-peat media. In the upper Vs samples of the vertical profile, no change occurred in the water tension points of all media; however, in the lower ⅓ samples, the moisture of both 2B : IP : IS and 3GR : IP increased. Total pore space of all media tested varied initially but did not change over time. Bark gained easily available water and water buffer capacity, and lost air space. Gasifier residue lost easily available water but was stable in all other measured factors. The 2-bark : 1-peat : 1-sand medium lost air space over time but gained easily available water and water buffer capacity, thus increasing in moisture. The 2-GR : 1-peat : 1-sand medium retained its initial air space and water buffer capacity, but lost easily available water. The 3-GR : 1-peat medium similarly lost easily available water over time.
To identify components of a possible signal transduction pathway associated with woody plant cold acclimation, a cDNA library prepared from peach bark collected in December was screened using a small DNA fragment from a maize receptor-like protein kinase (ZMPK1) as probe. Six isolates were obtained and partially sequenced to confirm protein kinase identity. One isolate (PPPKB5) contained a relatively large insert (about 1.9 kbp) and was selected for further analysis. Both strands of PPPKB5 were sequenced and the derived amino acid sequence was compared with a variety of known plant protein kinases, leading to the tentative identification of this clone as encoding a partial cDNA for a serine/threonine class protein kinase. PPPKB5 has a classic protein kinase catalytic domain with all the features required for phosphorylation activity and with greater similarity to the known plant receptor-like protein kinases (RLKs) than other classes of these enzymes. In addition, it contains a potential transmembrane region separating the catalytic portion of the molecule from the receptor region. The receptor region has greatest identity with the class of RLKs known as the S-locus type based on conservation of a stretch of 10 cysteines on the amino-terminal side of the transmembrane region. PPPKB5 shares greater amino acid identity with ZMPK1 (50%) than with the Brassica, rice or Arabidopsis S-locus RLKs (34%–40%). Furthermore, PCR analysis of `Loring' suggests that, like maize ZMPK1, the genomic sequence encoding PPPKB5 contains no introns, in contrast to the genomic sequences of Brassica and Arabidopsis which contain six.
Many industrial and agricultural wastes have been evaluated for use as alternative container substrate components. Recently, a new material produced from ground pine logs (Pinus taeda L.) has been utilized as a substitute for peat moss and pine bark (PB). On 17 Aug. 2005, japanese holly (Ilex crenata `Compacta' Thunb.) plants were potted in milled PB (Pinus taeda L.) and debarked ground pine chips (PC). Pine chips were ground with a hammermill to pass through a 6.35-mm screen. Osmocote Plus 15–9–12 (15N–4P–10K) was incorporated in both PB and PC substrates at the rates of 3.5, 5.9, 8.3, and 10.6 kg·m-3. Plants were greenhouse grown until 22 Nov. 2005. Substrate solution nutrient content and pH were determined for all treatments in each substrate. Shoots were dried, weighted, and tissue analyzed for N, P, K, Ca, Mg, S, Fe, Cu, Mn, and Zn. Shoot weights were higher in plants grown in PB than PC at the 3.5 and 5.9 kg·m-3 fertilizer rates. At the 8.3 kg·m-3 rate, shoot dry weight was about the same for each substrate, but at the 10.6 kg·m-3 rate, growth was higher for plants grown in PC than in PB. Substrate EC increased with increasing fertilizer rates and with the exception of Cu, was higher in PB substrates at all fertilizer rates. Plant tissue levels generally increased as fertilizer rate increased in both substrates but were higher in plants grown in PB than PC with the exception of Cu. Therefore, higher rates of fertilizer are required to produce optimal plant growth in PC compared to PB.