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Luther Waters Jr., Bonnie L. Blanchette, Rhoda L. Burrows, and David Bedford

High levels of sphagnum peat in the growing medium promoted growth of asparagus (Asparagus officinalis L. cv. Viking 2K) in a greenhouse study. Application of NH4NO3 > 1 g/pot (84 kg·ha-1 equivalent) was detrimental to root growth. High N rates and high organic matter levels decreased fibrous root development. Shoot dry weight was highly correlated with fleshy root number, root dry weight, and shoot vigor.

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Daniel Leskovar and Yahia Othman

). This is because transplant root growth in the field is related to management practices (e.g., N level supplied) during the transplant stage in the greenhouse ( Liptay and Nicholls, 1993 ). The use of FL fertigation system in the nursery period allowed

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Jeff S. Kuehny, William B. Miller, and Dennis R. Decoteau

Rooted cuttings of Ligustrum japonicum Thunb., an episodically growing species, were grown hydroponically in a controlled-environment growth chamber to determine allocation of glucose, mannitol, total soluble sugars, and total protein in mature leaves, flush leaves, stems, and roots. During the 65 days of episodic growth, 43% of the total soluble sugars was glucose and 33% mannitol. Glucose concentrations of mature leaves decreased during the first root growth episode, increased in almost all plant tissue during a shoot growth episode and decreased in all plant tissue at initiation of a second root growth episode. Mannitol concentrations in the roots and stems decreased during episodes of root growth and increased during a shoot growth episode when leaf flush mannitol concentrations increased. Radiolabeled C applied to leaves before the initiation of the first period of shoot elongation was translocated to the roots. After shoot elongation, just before a root growth episode, most labeled C was translocated to new shoots and roots. Autoradiographs indicated that subsequent episodes of shoot growth were supported by photosynthate from the previous shoot flush. Protein concentrations decreased in all plant tissues during shoot growth but increased in roots and mature leaves during root growth. Concentrations of 15N in leaf and stem tissue indicated retranslocated N supported each episode of shoot growth. Changes in endogenous C and N concentrations and allocation patterns in ligustrum were linked to the control of episodic shoot and root growth.

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Ken Takahata and Hiroyuki Miura

hand around the lower parts of the stems would result in impeded translocation of photosynthates to the roots, which suppresses root growth and water absorption by the roots, like the treatment of salt or water stress. This also impeded the transport of

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Daniel I. Leskovar, Daniel J. Cantliffe, and Peter J. Stoffella

`Sunny' tomato (Lycopersicon esculentum Mill.) containerized transplants were grown with the standard or conventional systems (SS) and with recently developed flotation systems (FS). Standard system and FS transplants, and direct-seeding using coated seeds were evaluated in the field for root and shoot growth and yield at Parrish, Bradenton, and Naples during fall, winter, and spring plantings. Plant growth characteristics were measured weekly before, during, and after transplanting or sowing. In the Parrish and Bradenton Fall 1987 and Bradenton Spring 1988 experiments, SS transplants had greater leaf area, root volume, shoot dry weights, and shoot: root ratios than FS transplants. During early development, the FS transplants had more lateral root growth than SS transplants, but had similar total root growth and horizontal and vertical root distribution after transplanting in the field. Transplants and direct-seeded plants allocated 72% of the total root mass in the upper 0 to 10 cm of the soil. In Fall 1987, SS transplants had between 29% and 41% more fruit yield than FS transplants at Bradenton and Parrish, respectively. In the Naples Winter 1988 and Parrish and Bradenton Fall 1989 experiments, both transplant types had similar fruit yields, but more than direct-seeded plants. Transplants grown with the flotation system are recommended for use provided that seedlings are grown and maintained with minimum hardening before establishment in the field.

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Edward F. Gilman and Michael E. Kane

Shoot and root growth were measured on Chinese juniper (Juniperus chinensis L. `Torulosa', `Sylvestris', `Pfitzeriana', and `Hetzii') 1, 2, and 3 years after planting from 1l-liter black plastic containers. Mean diameter of the root system expanded quadratically, whereas mean branch spread increased linearly. Three years after planting, root spread was 2.75 times branch spread, and roots covered an area 5.5 times that covered by the branches. Percentage of total root length located within the dripline of the plants remained fairly constant for each cultivar during the 3 years following planting. Root length density increased over time but decreased with distance from the trunk. During the first 2 years after planting, shoot mass increased faster than root mass. In the 3rd year, the root system increased in mass at a faster rate than the shoots. Root length was correlated with root weight. Root spread and root area were correlated with trunk cross-sectional area, branch spread, and crown area.

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Carleton B. Wood, Timothy J. Smalley, Mark Rieger, and David E. Radcliffe

Container-grown Viburnum plicatum Thunb. var. tomentosum (Thunb.) Miq. `Mariesii' were planted in unamended planting holes, tilled plots, and tilled plots amended with aged pine bark. A 36-day drought was initiated 108 days after planting. Amending induced N deficiencies, reduced shoot growth, and increased root growth. Plants harvested from tilled and planting-hole plots at drought initiation had 63% and 68% more dry weight, respectively, than plants from amended plots. Between 8 and 19 days after drought (DAD) initiation, plants from tilled plots maintained higher relative leaf water content (RLWC) than plants from planting holes. Plants in amended plots maintained higher RLWC than both other treatments between 7 and 33 DAD. Amended and tilled treatments had higher relative leaf expansion rates (RLERs) than the planting-hole treatment 8, 11, 13, and 15 DAD. As the drought lengthened, plants in amended plots maintained higher RLERs than plants in tilled plots. While plants in pine bark-amended plots were more drought tolerant than those in tilled plots, it is unclear if increased drought tolerance was caused by the improved rooting environment or N deficiency.

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Daniel I. Leskovar, Daniel J. Cantliffe, and Peter J. Stoffella

Studies were conducted to evaluate growth of tomato (Lycopersicon esculentum Mill.) transplants in the field in response to age of transplants in Spring and Fall 1989. Transplants were 2 (2W), 3 (3W), 4 (4W), 5 (SW), or 6 (6W) weeks old. Drip and subseepage irrigation were used. In spring, older transplants produced more shoot and root growth up to 2 (T2) weeks after transplanting. At 3 (T3) and 4 (T4) weeks after transplanting, there were no differences between 4W, 5W, and 6W transplants. These trends were independent of irrigation systems. Total yield and early yield were similar for all transplant ages. In fall, shoot growth increased linearly with increasing transplant age at TO, but not thereafter. Chlorophyll a + b increased over time, but no treatment differences were found at T4. At planting, 2W transplants had a higher Chl a: b ratio than older transplants. This difference was reduced at T1 and T2 and became insignificant at T4. These results indicate that no improvement in yields was obtained using the traditional older transplants. Younger transplants might be used to achieve rapid seedling establishment with-minimal transplant production costs.

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Dariusz Swietlik and Linsen Zhang

Chelator-buffered nutrient solutions were used to study the effect of different levels of Zn activity in the rhizosphere on growth and nutritive responses of various tissues of sour orange seedlings. The seedlings were grown for 3 months in a growth chamber in a hydroponic culture containing from 5 to 69 μm and 5 to 101 μm total Zn in Expts. 1 and 2, respectively. Zn+2 activities were calculated with a computerized chemical equilibrium model (Geochem-PC), and buffered by inclusion of a chelator, diethylenetriamine pentaacetate (DTPA), at 74 and 44 μm in excess of the sum of Fe, Mn, Zn, Cu, Ni, and Co in Expts. 1 and 2, respectively. The use of DTPA-buffered solutions proved successful in imposing varying degrees of Zn deficiency. The deficiency was confirmed by leaf symptomatology, leaf chemical analyses, i.e., <16 mg·kg-1 Zn, and responses to foliar sprays and application of Zn to the roots. Growth parameters varied in their sensitivity to Zn deficiency, i.e., root dry weight < leaf number and white root growth < stem dry weight < leaf dry weight < shoot elongation and leaf area. The critical activities, expressed as pZn = -log(Zn+2), were ≈10.2±0.2 for root dry weight, 10.1±0.2 for leaf number and white root growth, 10.0±0.2 for stem dry weight, 9.9±0.2 for leaf dry weight, and 9.8±0.2 for shoot growth and leaf area. Increases in growth were observed in response to Zn applications even in the absence of visible Zn-deficiency symptoms. Seedlings containing >23 mg·kg-1 Zn in leaves did not respond to further additions of Zn to the nutrient solution. Zinc foliar sprays were less effective than Zn applications to the roots in alleviating severe Zn deficiency because foliar-absorbed Zn was not translocated from the top to the roots and thus could not correct Zn deficiency in the roots.

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Chris A. Martin, Jean C. Stutz, and Robert W. Roberson

Effects of VAM fungal inoculum, Glomus intraradices Schenk & Smith, on the growth of Chilean mesquite in containers were investigated as part of a nursery container system for production of xeric trees. Seedling liners of Chilean mesquite were transplanted into 27-liter containers filled with a 3 pine bark : 1 peat moss : 1 sand medium. Before transplanting, 50% of the trees were band-inoculated at a depth of 8 to 12 cm below the growth medium surface with 35 g per container of Glomus intradices (Nutrilink, NPI, Salt Lake City, UT), approximately 1,000 spores g-1. All trees were top-dressed with 15 g Osmocote 18N-2.6P-9.9K (Grace-Sierra, Milpitas, CA) and 3 g Micromax (Grace-Sierra, Milpitas, CA) fertilizers and grown in a fiberglass greenhouse under 50% light exclusion. After 4 months, all inoculated tree root systems were colonized, and the percent infection was 47%. Noninoculated trees remained nonmycorrhizal. There were no differences in height, total shoot length, shoot dry weight, or root dry weight between inoculated and non-inoculated trees; however, total root length and specific root length of inoculated trees were less than those of noninoculated trees. These results suggest that the VAM fungi altered the root architecture of inoculated trees such that root systems of these trees had thicker roots with fewer fine roots elongating into the growth medium profile.