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Anne K. Hurley and B. Greg Cobb

Cucumis sativus, L., `Poinsett' seedlings were grown under artificial light in 40% modified Hoagland's solution until an average plant plastochron index of 4.73 was reached. Plants were then placed in solutions of (1) 0 mM NaCl, (2) 80 mM NaCl (salt-shock), or (3) placed in a dropwise gradient solution of NaCl and Hoagland's until the final concentration of 80 mM NaCl was reached at 41 hours. Leaves of the 80 mM shock treatment wilted immediately, but recovered turgor within 6 hours. Leaves of 80 mM gradient did not wilt at anytime. The control and gradient treatments had relative growth rates which were similar to each other, but RGR decreased in the shock treatment. Invertase activity was measured in the roots at 24, 41, and 48 hours after initial treatment. Invertase activity of shock treatment increased significantly over the controls at 24 hours. The 80mM gradient was not significantly different than either treatment. Four isozymes of α– galactosidase were detected. The relative intensities of the bands varied with time and treatment. One invertase band was resolved in roots on 8% native acrylamide gels. SDS gels indicated increases in proteins in the gradient treatment compared to the control and the 80 mM shock treatment.

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Anne K. Hurley and B. Greg Cobb

Cucumis sativus, L., `Poinsett' seedlings were grown under artificial light in 40% modified Hoagland's solution until an average plant plastochron index of 4.73 was reached. Plants were then placed in solutions of (1) 0 mM NaCl, (2) 80 mM NaCl (salt-shock), or (3) placed in a dropwise gradient solution of NaCl and Hoagland's until the final concentration of 80 mM NaCl was reached at 41 hours. Leaves of the 80 mM shock treatment wilted immediately, but recovered turgor within 6 hours. Leaves of 80 mM gradient did not wilt at anytime. The control and gradient treatments had relative growth rates which were similar to each other, but RGR decreased in the shock treatment. Invertase activity was measured in the roots at 24, 41, and 48 hours after initial treatment. Invertase activity of shock treatment increased significantly over the controls at 24 hours. The 80mM gradient was not significantly different than either treatment. Four isozymes of α– galactosidase were detected. The relative intensities of the bands varied with time and treatment. One invertase band was resolved in roots on 8% native acrylamide gels. SDS gels indicated increases in proteins in the gradient treatment compared to the control and the 80 mM shock treatment.

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Pauline P. David, Audrey A. Trotman, and Desmond G. Mortley

One of the major objective of growth analysis data is to provide a basic understanding of some of the mechanisms that affect plant growth. This study was initiated to evaluate the effects on several growth parameters when plants are grown in an NFT system. Vine cuttings (15 cm length) of the sweetpotato cultivar ``Georgia Jet” was grown in a closed NFT system for a period of 120 days. Nutrient was supplied in a modified half-strength Hoagland's solution with a N:K ratio of 1:2.4. Destructive harvesting of plants occurred at 14 day intervals at which time plants were separated into their various component parts and analyzed for dry weight accumulation, leaf area index, crop growth rate, relative growth rate and net assimilation rate. Results showed dry weight distribution within the plant had a linear response for all component part evaluated. Greatest contributors to total plant dry weight was stem followed by leaves, fibrous roots, buds and flowers. However, once storage root production occurred it contributed the largest percentage to total plant dry weight. LAI was optimum at 80 days after planting (DAP) while CGR and RGR fluctuated throughout the growing season. Initially NAR was higher in foliage than storage roots but declined once storage root enlargement began, suggesting a translocation of assimilates to storage root.

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C.R. Clement and R.M. Manshardt

The pejibaye (Bactris gasipaes Kunth) is being evaluated in Hawai'i for its fresh heart of palm, a gourmet vegetable. Seven half-sib progenies of the Putumayo land race were planted in a split-plot design, with densities (3333, 5000, 6666 plants/ha) as the main plots, progenies as the sub-plots, three replications, and nine plants/plot. Precocity was defined as “days from planting to harvest”; relative growth rate (RGR) and unit leaf rate (Ea) are possible causes of precocity and were estimated for the period from 6 months after planting to harvest. Density effects were never significant, suggesting that competition is not significant before harvest. Mean precocity ranged from 610 to 712 days; Va accounted for 14% of the phenotypic variance (Vp), with h2 = 0.57, similar to fruiting precocity in African oil palm (Elaeis guineensis Jacq.). Mean Ea ranged from 1.89 to 2.21 g/m2 per day, Va accounted for 8% of Vp, with h2 = 0.33 Mean RGR ranged from 0.0086 to 0.0102 d–1; Va accounted for 9% of Vp, with h2 = 0 35 Neither RGR (r = 0.20) nor Ea (r = 0.19) are significantly correlated with precocity. Heart, edible stem, and total edible product weights did not present significant progeny effects, probably because of the criterion used to determine harvest (height = 1.3 m). Precocity is easiest to work with and should give acceptable genetic gains.

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Paul T. Wismer, J.T.A. Proctor, and D.C. Elfving

Benzyladenine (BA), carbaryl (CB), daminozide (DM), and naphthaleneacetic acid (NAA) were applied postbloom, as fruitlet thinning agents, to mature `Empire' apple trees. Although fruit set and yield were similar for BA, NAA, and CB, BA-treated fruit were larger, indicating BA increased fruit size beyond the effect attributable to thinning. BA applied at 100 mg·liter–1 increased the rate of cell layer formation in the fruit cortex, indicating that BA stimulated cortical cell division. The maximum rate of cell division occurred 10 to 14 days after full bloom (DAFB) when fruit relative growth rate and density reached a maximum and percent dry weight reached a minimum. Cell size in BA-treated fruit was similar to the control. Cell division ended by 35 DAFB in the control and BA-treated fruit when percent dry weight and dry weight began to increase rapidly and fruit density changed from a rapid to a slower rate of decreased density. These data support the hypothesis that BA-induced fruit size increases in `Empire' apple result largely from greater numbers of cells in the fruit cortex, whereas the fruit size increase due to NAA or CB is a consequence of larger cell size.

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Thomas E. Marler, Louann C. Guzman, and John H. Lawrence

Acacia auriculiformis, A. mangium, and A. koa trees were grown in 5.4-liter containers under conditions of 100%, 44%, or 19% sunlight transmission to determine biomass accumulation and partitioning and phyllode gas-exchange responses to developmental light level. Following ≈100 days of growth, all three species exhibited a linear decrease in relative growth rate and biomass accumulation in response to developmental light level. The influence of reduced developmental light level on growth was similar for the three species, with biomass accumulation under 19% transmission averaging ≈20% of that under full sunlight. In a second study, the diurnal pattern of gas exchange of mature phyllodes was determined. Gas exchange of phyllodes under 19% or 44% transmission depended on photosynthetic photon flux throughout the day. In contrast, gas exchange of phyllodes in 100% transmission was highest in early to midmorning on sunny days. Phyllode gas exchange slowly declined thereafter for A. mangium and A. koa, but rapidly declined then slightly recovered in late afternoon for A. auriculiformis.

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Yiqin Ruan and Mark H. Brand

Rhododendron `Montego' shoot cultures initiated from plants with and without tissue proliferation (TP and NTP) served as explant sources for all studies (Note: in vitro TP shoot cultures produce primarily dwarf shoots, some long shoots, and stem tumors). Calli induced from TP leaves and tumors and NTP leaves were cultured on woody plant (WP) medium containing NAA and 2-iP. During the first 4 weeks of culture, calli from NTP leaves had higher relative growth rates than calli from TP leaves or tumors. However, calli from TP leaves and tumors grew faster than calli from NTP leaves for all subculture periods that followed. Shoot tips (5 mm) were excised from TP dwarf shoots, TP long shoots, and NTP shoots and were cultured on WP medium with or without 15 μM 2-iP. Shoot tips from TP dwarf and long shoots multiplied on medium without 2-iP, averaging 18.4 and 1.7 shoots per shoot tip in 12 weeks, respectively. Shoot tips from NTP shoots only multiplied when maintained on 2-iP-containing medium. When placed on 2-iP-containing medium, both types of TP shoot tips produced clusters of callus-like nodules that gave rise to highly tumorized, short shoots or leafy meristems.

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John R. Teasdale, Aref A. Abdul-Baki, and William J.E. Potts

Dry weight and leaf area of tomato (Lycopersicon esculentum Mill.) plants grown on raised beds with black polyethylene (BP) or hairy vetch (Vicia villosa Roth) (HV) mulches were measured at weekly intervals during 1993 and 1994. Leaf area and foliage, fruit, and total weight of tomato plants grown in BP were greater early in the season, but less later in the season than plants grown in HV. The relative growth rate of tomatoes in HV was higher throughout most of each year than that in BP. There was little difference between treatments in unit leaf rate (rate of weight gain per unit leaf area). The growth rate of fruit per unit of tomato foliage was greater in BP than HV, whereas the leaf area to weight ratio was greater in HV than BP. These results suggest that tomatoes grown in BP produce greater early yield because of greater early foliage growth and greater partitioning to fruit than HV. However, tomatoes grown in HV eventually outgrow and outyield those in BP because of greater partitioning to and maintenance of leaf area throughout the season.

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Puffy Soundy, Daniel J. Cantliffe, George J. Hochmuth, and Peter J. Stoffella

Although floatation irrigation has numerous advantages for vegetable transplant production, including improved seedling health, lettuce (Lactuca sativa L.) transplants grown with floatation (ebb and flow) irrigation can have poor root systems. Floatation fertigation of `South Bay' transplants with K at 15, 30, 45, or 60 mg·L-1 K applied every 2 to 4 days, increased fresh and dry root weight at 28 days. Higher K (24 mg·kg-1) in the medium did not affect root weight. Fresh and dry shoot weight, leaf area, relative shoot ratio (RSR), relative growth rate (RGR), leaf weight ratio (LMR), and root weight ratio (RMR) were unaffected by applied K, regardless of the initial K concentration in the medium. Available K in a vermiculite-containing medium may have supplied all the K required. When 60 was compared with 100 mg·L-1 N at various levels of K, the applied K again did not influence dry root weight; however, at 100 mg·L-1 N, root weight was reduced as compared with 60 mg·L-1 N, regardless of the level of applied K. In a field experiment, pretransplant K had no effect on growth. Transplants grown with no added K in a peat + vermiculite mix with at least 24 mg·L-1 water-extractable K produced yields equivalent to transplants supplied with 15, 30, 45, or 60 mg·L-1 K via floatation irrigation.

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Gina E. Fernandez, Laura M. Butler, and Frank J. Louws

The growth and development of three strawberry cultivars commonly grown in a plasticulture system were documented. Strawberry plants were harvested monthly and divided by roots, crown, leaves, flowers, and fruit and then dried in an oven. The dry matter production and resource allocation proceeded along a predictable pattern of development. The establishment phase was characterized by an active period of growth of root, crown and leaves in the fall. Through the winter, the plants underwent slow growth, ending in a transition period in the late winter/early spring when resources were allocated to both vegetative and reproductive growth. In the spring, all plant parts received significantly increased allocation of, or redistribution of, resources. Cultivars of California origin, `Chandler' and `Camarosa', displayed similar trends in yield, dry matter production, seasonal resource allocation, and growth analysis variables throughout the season. `Sweet Charlie', a cultivar from Florida, showed lower dry matter accumulation and relative growth rate in the spring, higher harvest index and lower yield than the California cultivars.