often removed only partially, and thus, meristem regrowth occurs. Even in the most sophisticated grafting operations today, 2% to 3% of grafted plants will have rootstock regrowth (G. Causarano, personal communication). Additionally, if the regrowth is
occurs. The extent of meristem regeneration varies widely and is dependent on the method used, timing of grafting, and the experience of the individual doing the grafting. Rootstock meristem regrowth also contributes greatly to the cost associated with
remaining cotyledon ( Dabirian and Miles, 2017a ; Hassell et al., 2008 ; Memmott and Hassell, 2010 ). Yet rootstock bud meristem tissue may be only partially removed because it is difficult to see, and rootstock regrowth, sometimes referred to as
In this field study, five preemergence and two postemergence herbicides were evaluated for their ability to hasten Meyer zoysiagrass (Zoysia japonica Steud.) sod development when sod was established from the regrowth of rhizomes, sod strips, and loosened plant debris. Herbicide influence on zoysiagrass re-establishment was examined using two postharvest field preparation procedures as follows: area I was raked to remove most above-ground sod debris, whereas in adjacent area II sod debris was allowed to remain in place. Herbicides that controlled smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl.] generally enhanced zoysiagrass cover by reducing weed competition. Meyer established from rhizomes, sod strips, and loosened plant debris, and treated with herbicides, had a rate of sod formation equivalent to that expected in conventionally tilled, planted, and irrigated Meyer sod fields. Effective smooth crabgrass control was achieved when the rates of most preemergence herbicides were reduced in the 2nd year. Chemical names used: dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate (DCPA); 3,5,-pyridinedicarbothioic acid, 2-[difluromethyl]-4-[2-methyl-propyl]-6-(trifluoromethyl)∼S,S-dimethyl ester (dithiopyr); [±]-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy] propanoate (fenoxaprop); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); N-[1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine(pendimethalin);N3,N3-di-n-propyl-2,4-dinitro-6-[trifluromethyl)-m-phenylenediamine (prodiamine); and 3,7-dichloro-8-quinolinecarboxylic acid (quinclorac).
Podophyllotoxin is a pharmaceutical compound extracted from rhizomes of Indian mayapple (Podophyllumemodi). Leaves of American mayapple (P. peltatum) also contain podophyllotoxin, and the species is being investigated as a domestic, renewable, and alternative source of the compound. The objective of this study was to explore strategies of leaf removal that would not adversely affect regrowth of American mayapple shoots in subsequent years. Plots were established in two locations among naturally occurring populations in the wild, one in full sun and one in partial shade. Plots were 1.0 m2 and leaves were removed from plants every spring, every other spring, or every third spring. In addition, leaves were removed in early spring, soon after shoots emerged and leaves had fully expanded, or in late spring, when leaves first showed evidence of yellowing and beginning to senesce. Sexual and asexual leaves were harvested separately. Leaf number, leaf area, and dry weight were recorded. Subsamples of leaf material were extracted to determine podophyllotoxin, α-peltatin, and β-peltatin contents. Results clearly showed that leaf removal every year, in combination with early harvest, was too severe and plants lost vigor over the 4-year period of this study. Plants subjected to this treatment combination produced significantly less leaf area and dry weight than any of the other treatment combinations. Results were similar for both sun and shade locations. Lignan content was not affected by treatment. Our results indicate that leaves can be removed from mayapple plants as often as every year provided harvests are not scheduled too soon after shoot emergence.
Treatment of headed-back 1-year-old dormant shoots of ‘Monroe’, ‘McIntosh’ and ‘Wayne’ apple (Malus domestica Borkh.) with 1% naphthaleneacetic acid (NAA) in latex paint was relatively ineffective and gave inconsistent results; however, treatment of mechanically hedged shoots on established trees gave statistically significant reductions in regrowth, by reducing bud break of dormant buds on older wood. Regrowth in ‘Monroe’ trees was reduced with daminozide primarily by reducing shoot length.
During freezing studies of `Concord' grape (Vitis labrusca L.), bud viability significantly affected callus formation, adventitious root initiation, and root dry weight during regrowth assays conducted to assess freezing injury. Applying exogenous 1- H -indole-3-acetic acid (IAA) partially offset bud loss and stimulated root initiation. Further tests demonstrated that buds were less cold hardy than internode woody tissues in dormant `Concord' canes. Because of cold-hardiness differences between buds and wood and because bud viability affects callus formation, root initiation, and root dry weight, regrowth assays do not seem to be sensitive indicators of freezing injury in grape woody tissues. Regrowth assays, however, seem to be reliable indicators of overall viability for frozen `Concord' grape cuttings.
Vigorous, young trees of ‘Topred Delicious’ apple (Malus domestica Borkh.) either dormant-pruned or left unpruned at the end of the previous season, were summer-pruned at 8, 12, 16, or 20 weeks after full bloom (WAFB) by thinning, heading, or stubbling current season to 2-year-old shoots. The amount of new growth following summer pruning (regrowth) was influenced by the date of pruning; late pruning (20 WAFB) generally produced less regrowth than earlier pruning (8 WAFB). Regrowth also varied with moisture conditions during 2 growing seasons. Severe heading or stubbing of vigorous vegetative shoots to 2 or 3 nodes resulted in flower bud initiation on some spurs produced from axillary buds on these stubs. The degree of fruit bud initiation was related to time of pruning and moisture supply. Summer pruning generally increased the percentage of sunburned fruit harvested, but there was no consistent effect on fruit size, color, flesh firmness, or soluble solids.
Crown divisions of Campanula takesimana were potted 1 Sept. 1994 and were grown under natural conditions until 19 Nov., when they were moved into a 3 °C greenhouse. On 15 Feb. 1995, 10 plants were randomly assigned to each of four temperature treatments (−5, −8, −11, and −14 °C), using each of four freeze acclimation procedures designated A through D: group A plants were held at treatment temperatures for 30 minutes; group B plants were first subjected to three alternating freeze-thaw cycles (−3 °C for 24 hours, 3 °C for 24 hours), then held at treatment temperatures for 30 min; plants in group C were held at −1 °C for 14 days and subsequently were exposed to treatment temperatures for 30 minutes; group D plants were held at treatment temperatures for 48 hours. A control group was held at 3 °C for the duration of the study. Following 6 weeks regrowth at 15 °C, plants were rated for survival and regrowth quality relative to unfrozen controls. At treatment temperatures of −8 °C and less, acclimation procedure significantly influenced survival and regrowth quality. Plants exposed to three freeze-thaw cycles had the highest regrowth ratings at treatment temperatures less than −5 °C, with no loss in marketability following exposure to −11 °C. In addition, all plants exposed to freeze-thaw cycles thrived following controlled freezing, whereas those in each of the other groups displayed a decline in survival with decreasing treatment temperatures. Holding plants for 14 d at −1 °C had no beneficial effect on survival or regrowth quality relative to plants held at constant above-freezing temperatures. Increasing exposure duration from 30 minutes to 48 hours significantly reduced regrowth quality at treatment temperatures of −8 °C and −11 °C.
Sprays of ammonium ethyl carbamoyl-phosphonoate (Krenite), applied to the tops of mature Lisbon lemon trees [Citrus limon (L). Burml.] resulted in significant inhibition of re-growth for over 3 years. One spray increased yield over the control trees (hand topped annually), while 2 sprays reduced yield. The sprays did not effect the N concentration in the leaves.