of salinity stress, to develop efficient crop cultivation practices and breeding strategies. From the literature review, it became evident that a very limited number of studies have evaluated the effect of salinity stress on physiology and root growth
Ved Parkash and Sukhbir Singh
Michael A. Arnold and Eric Young
CuCO3 at 100 g·liter-1 in a paint carrier applied to interior container surfaces effectively prevented root deformation in container-grown Malus domestica Borkh. and Fraxinus pennsylvanica Marsh. seedlings. CuCO3 treatments nearly doubled the number of white unsuberized root tips in both species. CuCO3 treatment increased some measures of root and shoot growth before and after transplanting to larger untreated containers. Root pruning at transplanting tended to reduce root and shoot fresh and dry matter accumulation in F. pennsylvanica seedlings and shoot extension in M. domestica seedlings. In some cases, root pruning of M. domestics at transplanting from CuCO3-treated containers increased root growth compared to unpruned CuCO3-treated and untreated seedlings. Changes in growth induced by CuCO3 and root pruning were not related to changes in trans -zeatin riboside-like activity in the xylem sap of-apple.
Qingzhang Xu, Bingru Huang, and Zhaolong Wang
Turf quality of creeping bentgrass (Agrotis palustris L.) often declines during summer months. Reducing soil temperature alleviates bentgrass quality decline at supraoptimal air temperatures. The objective of this study was to investigate whether reducing soil temperature during the night is more effective than during the day in improving shoot and root growth when air temperature was supraoptimal for creeping bentgrass. The experiment was conducted in growth chambers using water baths to manipulate soil temperatures. Plants were exposed to the following temperature treatments: 1) optimal air and soil temperature during the day and night (20/20 °C, day/night, control); 2) high air and soil temperature during the day and night (35/35 °C, day/night); 3) lower soil temperatures during the day (20/35, 25/35, and 30/35 °C, day/night); and 4) lower soil temperature during the night (35/20, 35/25, and 35/30 °C) while air temperature was maintained at 35 °C during the day and night. Turf quality (on 1-9 scale) increased to the level of 6.5, 3.0, and 2.5 by reducing day soil temperature to 20, 25, or 30 °C, respectively, at 28 days of treatment, compared to the quality of 2.0 at 35/35 °C. Turf quality increased from 2.0 at 35/35 °C to 7.0, 6.0, and 4.5, respectively, by 28 days of exposure to night temperatures of 20, 25, and 30 °C. Chlorophyll content, root number, and root weight also were increased by reducing day or night soil temperature, and the increases were more pronounced for reduced night temperatures than day temperatures. These results demonstrated that reduced night soil temperature was more effective than reduced day soil temperature in improving shoot and root growth in creeping bentgrass under high air temperature conditions.
Rick M. Bates and Alexander X. Niemiera
Two-year-old Washington hawthorn (Crataegus phaenopyrum Med.) and Norway maple (Acer platanoides L.) seedlings were subjected to varying cold storage durations and four storage treatments: whole plant covered in polyethylene bags, shoots exposed, roots exposed, and whole plant exposed. After storage, half the seedlings were immediately plant and half received a 12-hour desiccation treatment before transplanting. Root growth potential (RGP), time to budbreak, and marketability were measured. With the root covered treatments, Norway maple RGP increased while Washington hawthorn RGP decreased with increased cold storage duration. RGP for both species remained low throughout storage for treatments exposing roots. The 12-hour desiccation treatment reduced RGP for both species with hawthorn being more affected than maple. Days to budbreak for both species decreased with increased storage time for whole plant covered treatments but increased for both species when stored with exposed roots. Maple marketability for root covered treatments was high for most storage durations. Hawthorn marketability was generally low except for the whole plant covered treatment during the first 6 weeks of storage. For the respective storage durations, hawthorn RGP, time to budbreak and marketability values for the shoots exposed treatment were similar to the root exposed treatments. In contrast, values for the shoots exposed treatment were similar to the whole plant covered treatment for maple. There was a high positive correlation between RGP and marketability for both species.
Rongcai Yuan, Ulrich Hartmond, Angela Grant, and Walter J. Kender
Influence of young fruit, shoot, and root growth on response of mature `Valencia' oranges [Citrus sinensis (L.) Osbeck] to the abscission chemical CMN-pyrazole was examined in 1999 and 2000. CMN-pyrazole dramatically increased ethylene production in mature fruit and reduced the fruit detachment force (FDF), except during a period of reduced response to CMN-pyrazole in early May when spring vegetative growth, young fruit of the following year's crop, and mature fruit were all on the trees. Removal of spring flushes, which included spring vegetative shoots and leafy and leafless inflorescences, prevented any young fruit and shoot growth, but did not inhibit root growth. However, trunk girdling in combination with removal of spring flushes not only prevented growth of young fruit and shoots but also inhibited root growth. During the responsive period, there were no differences in either ethylene production or FDF of CMN-pyrazole-treated mature oranges between 1) the nonmanipulated trees and those manipulated by either 2) removal of spring flushes alone, or 3) in combination with trunk girdling. However, during the less responsive period, ethylene production in CMN-pyrazole-treated mature oranges was significantly lower while the FDF was higher in nonmanipulated trees than in trees treated by either removal of spring flushes alone, or in combination with trunk girdling. There was no difference in either fruit ethylene production or FDF between trees manipulated by (2) removal of spring flushes alone, and (3) removal of spring flushes in combination with trunk girdling regardless of CMN-pyrazole application. Shoot growth terminated at least 2 weeks before the onset of the less responsive period. Removal of young fruit increased response of mature fruit to CMN-pyrazole during the less responsive period. This suggests that hormones from rapidly growing young fruit may be responsible for the occurrence of the less responsive period. Chemical name used: 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMN-pyrazole).
B.L. McMichael and J.J. Burke
Jon M. Wraith and Christopher K. Wright
William R. Argo and John A. Biernbaum
Rooted cuttings of `Gutbier V-l 4 Glory poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) were grown in 15-cm pots using two irrigation methods, two water-soluble fertilization schedules, and two preplant root-media fertilization rates. No difference in shoot growth occurred with either top watering with 33% leaching or subirrigation. The top 2.5 cm (top layer) contained nutrient concentrations up to 10 times higher than those measured in the remaining root medium (root zone) of the same pot with both irrigation methods. Constant applications of28 mol N/m3 water-soluble fertilizer (WSF) limited shoot and root growth as measured at 3 and 8 weeks compared to a weekly increase in the concentration of WSF from 0 to 28 mol N/m3 in 7 mol N/m3 increments over a S-week period. The additional incorporation of 0.27 kg·m-3 mineral N to Metro Mix 510 before planting had no effect on fresh- or dry-weight accumulation. When the root-medium surface was covered by an evaporation barrier, 46% less water and 41% less N fertilizer were applied to plants of similar size, and higher root-zone nutrient levels were maintained over the 8 weeks of the experiment. The evaporation barrier had the greatest effect on increasing root-zone nutrient concentrations and reducing the growth of subirrigated plants.
Paul Jennings and Mikal E. Saltveit
Unlike horticulturally mature fruit of `Dasher II' and `Poinsett 76' cucumbers (Cucumis sativus L.), two cultivars that differ significantly in their level of chilling tolerance, imbibing and germinating seeds of these two cultivars responded similarly to chilling temperatures (e.g., increases in fresh weight, time to radicle emergence, and root growth). `Dasher II' and `Poinsett 76' seeds were imbibed and germinated at 10 to 30C, and seeds germinated at 25C for 24 h were chilled at 2.5C for various durations. In comparison, seeds from an aged lot of `Poinsett 76' seed (1989) responded very differently from the 1992 seed lots in all experiments. The chilling tolerance level of germinating `Poinsett 76' seed varied with the seedling age as measured by resumption of root growth. Our results suggest that some factor that confers chilling tolerance is gradually lost during the early stages of germination following imbibition.
Lewis W. Jett, Gregory E. Welbaum, and Ronald D. Morse
Priming, a controlled-hydration treatment followed by redrying, improves the germination and emergence of seeds from many species. We compared osmotic and matric priming to determine which was the most effective treatment for improving broccoli seed germination and to gain a greater understanding of how seed vigor is enhanced by priming. Broccoli (Brassica oleracea L. var. italica) seeds were osmotically primed in polyethylene glycol (PEG 8000) at -1.1 MPa or matrically primed in a ratio of 1.0 g seed:0.8 g synthetic calcium silicate (Micro-Cel E):1.8 ml water at -1.2 MPa. In the laboratory, germination rates and root lengths were recorded from 5 to 42C and 10 to 35C, respectively. Broccoli seeds germinated poorly at >35C. Root growth after germination was more sensitive to temperatures >30C and <15C than radicle emergence. Matric and osmotic priming increased germination rate in the laboratory, greenhouse, and field. However, matric priming had a greater effect on germination and root growth rates from 15 to 30C. Neither priming treatment affected minimum or maximum germination or root growth temperatures. Both priming treatments decreased the mean thermal time for germination by >35%. The greater germination performance of matrically primed seeds was most likely the result of increased oxygen availability during priming, increased seed Ca content, or improved membrane integrity.