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Takashi Nishizawa and Kenji Saito

Tomato plants (Lycopersicon esculentum Mill `Ougata-fukuju' and `Korokoro') were grown in a soil or a hydroponic culture to study effects of rooting volume restriction on plant growth and carbohydrate concentrations. In soil culture, leaf lengths decreased linearly as container volume decreased, while plant height did not decrease linearly, irrespective of fruiting. The root to shoot ratio decreased in smaller volume containers, irrespective of fruiting, because dry mass accumulation in the stem and leaves was relatively less inhibited than that in the roots. Total plant dry mass did not differ between fruiting and deblossomed plants, irrespective of container volume. In hydroponic culture, plant height in small containers (37 cm3) was similar to that in large containers (2024 or 4818 cm3). The root to shoot ratio of the plants grown in small containers was lower than that of the plants grown in large containers, mainly due to less inhibition of the dry mass accumulation in the stem than in the leaves. When small containers were almost filled with roots (28 days after transplanting), soluble sugar and starch concentrations in leaves became ≈2-fold higher in the plants grown in small than in those grown in large containers. At the end of experiment (42 days after transplanting), sucrose and starch concentrations in the stem were higher in plants grown in small than in those grown in large containers. However, soluble sugar and starch concentrations in the leaves did not differ between treatments.

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Thomas E. Marler and Haluk M. Discekici

The influence of partial root volume irrigation on water relations and expansion of roots and leaves of papaya plants was determined using split root containers. In one study, `Tainung #1' and Solo #8 seedling roots were trained into four compartments until well-established, then water was withheld from 0, 1, 2, or 3 quadrants. Mid-morning stomatal conductance and predawn relative leaf water content were not affected by the irrigation treatments. Similarly, relative root water content in the dry quadrants was not different from that in the watered quadrants. In a second study, `Red Lady' seedling roots were trained into four compartments which contained a 13 × 13-cm plexiglass observation window. After the plants were well-established, watering was continued in one of 4 (1:4) or four of four (4:4) quadrants. Leaf midrib and root extension were measured at 06:00 and 18:00 hr each day. Daily growth of roots in the dry quadrants was reduced 25% below that in the watered quadrants, and midrib extension of the 1:4 plants was reduced ≈10% below that of the 4:4 plants. Irrigation treatments did not influence the percentage of growth occurring during the diurnal and nocturnal periods. The dry quadrants of 1:4 plants were almost devoid of fine roots. The number of root tips on the observation windows of the 1:4 plants was reduced 43% in the dry quadrants and increased 22% in the wet quadrant compared with that for the 4:4 plants.

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A.M. Boland, P.H. Jerie, P.D. Mitchell, I. Goodwin, and D.J. Connor

Individual and interactive effects of restricted root volume (RRV) and regulated deficit irrigation (RDI) on productivity and water use of peach trees [Prunus persica (L.) Batsch `Golden Queen'] were studied over 3 years (1992-95). Trees were grown in lysimeters of five different soil volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3) with either full or deficit (RDI) irrigation. In Years 3 and 4, fruit size was reduced by up to 30% on trees in the two smallest volumes. Tree water use was positively related to increasing soil volume (linear, P < 0.001; quadratic, P < 0.011) in all years ranging from 1.8 to 4.4 L·mm-1 Epan in the post-RDI period of Year 2. Water use of deficit-irrigated trees was less than fully irrigated trees and there was an interaction between soil volume and irrigation treatment during RDI. Water relations did not limit growth or productivity. Tree water use was reduced under root restriction as a consequence of canopy demand rather than leaf function. Results suggest that a combination of restricted root volume and development of water stress achieve the RDI response in the Goulburn Valley, Australia.

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A.M. Boland, P.H. Jerie, P.D. Mitchell, I. Goodwin, and D.J. Connor

Individual and interactive effects of restricted root volume (RRV) and regulated deficit irrigation (RDI) on vegetative growth and mineral nutrition of peach trees [Prunus persica (L.) Batsch (Peach Group) `Golden Queen'] were studied over 3 years (1992-95). Trees were grown in lysimeters of five different volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3) with either full or deficit (RDI) irrigation. Increasing soil volume increased vegetative growth as measured by trunk cross-sectional area (TCA) (linear and quadratic, P < 0.011) and tree weight (linear, P < 0.001) with the final TCA ranging from 29.0 to 51.0 cm2 and tree weight ranging from 7.2 to 12.1 kg for the smallest to largest volumes. Root density measured at the completion of the experiment decreased with increasing soil volume (linear and quadratic, P < 0.001) with root length density declining from 24.0 to 2.0 cm·cm-3. RDI reduced vegetative growth by up to 70% as measured by weight of summer prunings. Root restriction was effective in controlling vegetative vigor and is a viable alternative for control of vegetative growth. Mineral nutrition did not limit tree growth.

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Thomas E. Marler and Haluk M. Discekici

`Tainung 2' papaya seedlings were transplanted on 30 Jan. 1996 and irrigated with one, two, or three drip irrigation lines per row in one study and with 90°, 180°, or 360° microsprinkler spray patterns in a second study to determine the reproductive and vegetative growth responses to irrigation design. Variable irrigation duration was used to supply a homogeneous amount of water to each plant in the drip irrigation study. The trench profile method was used in the drip irrigation study, and a monolith method was used in the microsprinkler study to determine root distribution at the end of the dry season (30 May to 2 June). All fruits were harvested and weighed on 26 Aug. Roots proliferated underneath the drip lines during the dry season, and root concentration on the profile walls was inversely related to the number of drip lines. Root concentration underneath one drip line was 3.7 times greater, underneath two drip lines was 2.3 times greater, and underneath three drip lines was 1.9 times greater than root concentration in the non-irrigated zones. Roots also proliferated in the wetted zones of the microsprinkler spray patterns. Mean fruit weight and total harvested fruit weight did not differ among the irrigation treatments within each study. The results indicate that papaya roots are highly morphoplastic and proliferate in wetted zones under partial root volume irrigation. One drip line per row supplied ample irrigation coverage under the conditions of this study.

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Mara Grossman, John Freeborn, Holly Scoggins, and Joyce Latimer

development, roots were scanned at each harvest using WinRhizo (Regent Instruments Inc., Quebec, Canada) and analyzed to determine root surface area and root volume. Root surface area and volume were determined by first washing all media off roots by hand and

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G.H. Neilsen, P. Parchomchuk, D. Neilsen, R. Berard, and E.J. Hague

`Gala' apple (Malus domestica Borkh) on M.26 rootstock was subjected, in the first five growing seasons, to NP-fertigation and a factorial combination of treatments involving method and frequency of irrigation. Two types of emitters (drip or microjet) were used to apply the same quantity of water at high (daily), intermediate (about weekly) and low (about bi-weekly) irrigation frequencies. Although initial tree vigor and yield were higher for drip-fertigated trees, by the end of the study microjet fertigation produced larger trees of similar yield. These microjet fertigated trees had higher leaf P, K and Cu but lower leaf N, Mg, and Mn than drip-fertigated trees. Soil pH and extractable Mg and K concentrations were higher and extractable-P concentrations lower directly beneath microjet-emitters as a result of the larger fertigated soil volume relative to drip-emitters. High frequency irrigation improved tree growth but had less effect on leaf nutrient concentrations or soil chemical changes than lower frequency irrigation. Leaf N concentration was most affected by irrigation frequency, tending to decrease with daily irrigation.

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Darren J. Hayes and Bryan J. Peterson

before harvest. For cuttings rooted in overhead mist, square root transformations were performed on root volume, root dry weight, and root tip counts to improve normality. For cuttings rooted by subirrigation, a cube root transformation was performed on

Open access

Dennis N. Katuuramu, W. Patrick Wechter, Marcellus L. Washington, Matthew Horry, Matthew A. Cutulle, Robert L. Jarret, and Amnon Levi

the major plant organ involved in water and nutrient acquisition and uptake ( Zhu et al., 2011 ). Root architecture and capacity (number of roots, root volume, length, and surface area) play an important role in water and nutrient acquisition, and in

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Kwang Jin Kim, Hyun Hwan Jung, Hyo Won Seo, Jung A. Lee, and Stanley J. Kays

media volume and root volume ratios using plants of about equal size that were growing in pots of differing diameters and media volumes. Materials and Methods Plant materials. Fatsia japonica (Thunb.) Decne. & Planch. and Dracaena fragrans (L.) Ker