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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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Timothy K. Broschat and Kimberly A. Klock-Moore

Areca palms [Dypsis lutescens (H. Wendl.) Beentje & J. Dransf.], spathiphyllums (Spathiphyllum Schott. `Figaro'), ixoras (Ixora L. `Nora Grant'), tomatoes (Lycopersicon esculentum Mill. `Floramerica'), marigolds (Tagetes erecta L. `Inca Gold'), bell peppers (Capsicum annuum L. `Better Bell'), and pentas [Pentas lanceolata (Forssk.) Deflers. `Cranberry'] were grown in a pine bark-based potting substrate and were fertilized weekly with 0, 8, 16, 32, or 64 mg (1.0 oz = 28,350 mg) of P per pot. Shoot, and to a much lesser extent, root dry weight, increased for all species as weekly P fertilization rate was increased from 0 to 8 mg/pot. As P fertilization was increased from 8 to 64 mg/pot, neither roots nor shoots of most species showed any additional growth in response to increased P. Root to shoot ratio decreased sharply as P fertilization rate was increased from 0 to 8 mg/pot, but remained relatively constant in response to further increases in P fertilization rate.

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Kirk W. Pomper, Desmond R. Layne and Snake C. Jones

The North American pawpaw [Asimina triloba (L.) Dunal] has great potential as a fruit crop or as a landscape plant. The influence of incident irradiance on pawpaw seedling growth and development in containers was examined in the greenhouse and outdoors. Root spiraling can be a problem for container-grown pawpaw seedlings; therefore, the influence of paint containing cupric hydroxide [Cu(OH)2] at 100 g·L-1 applied to the interior of containers on plant growth was also examined in a greenhouse environment. In pawpaw seedlings grown outdoors for 11 weeks, low to moderate shading levels of 28%, 51%, or 81% increased leaf number, total leaf area, and total plant dry weight (DW) compared to nonshaded seedlings. A shading level of 81% decreased the root to shoot ratio by half compared to nonshaded plants. Shading of 98% reduced leaf number, leaf size, and shoot, root, and total plant DW. Shading increased leaf chlorophyll a and b concentrations for pawpaw seedlings grown outdoors, while it decreased average specific leaf DW (mg·cm-2). In a separate greenhouse experiment, pawpaw seedlings subjected to shade treatments of 0%, 33%, 56%, 81%, or 98% did not respond as greatly to shading as plants grown outdoors. Greenhouse-grown plants had greater total and average leaf area under 33% or 56% shading than nonshaded plants; however, shading >56% reduced root, shoot, and total plant DW. Total shoot DW was greater in greenhouse grown plants with 33% shading compared to nonshaded plants. Pawpaw seedlings in control and most shade treatments (33% to 81%) in the greenhouse environment had more leaves and greater leaf area, as well as larger shoot, root, and total plant DW than seedlings in similar treatments grown outdoors. The greenhouse environment had a 10% lower irradiance, a 60% lower ultraviolet irradiance, and a significantly higher (1.23 vs. 1.20) red to far-red light ratio than the outdoors environment. Treatment of container interiors with Cu(OH)2 decreased total and lateral root DW in nonshaded seedlings, and it adversely affected plant quality by causing a yellowing of leaves and reduction of chlorophyll levels by the end of the experiment in shaded plants. Growth characteristics of pawpaw seedlings were positively influenced by low to moderate shading (28% or 51%) outdoors and low shading (33%) in the greenhouse. Seedlings did not benefit from application of Cu(OH)2 to containers at the concentration used in this study. Commercial nurseries can further improve production of pawpaw seedlings using low to moderate shading outdoors.

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Amy L. Burton, Svoboda V. Pennisi and Marc W. van Iersel

. Species-specific responses have been documented for various growth parameters, such as growth index, dry weight, and root-to-shoot ratio ( Conover and Poole, 1981 ). In addition, production irradiance also affects acclimation. Because the majority of

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Dilma Daniela Silva, Michael E. Kane and Richard C. Beeson Jr.

extreme cases, not achieved at all. This delay requires additional water, fertilizer, and extended care. The root-to-shoot ratio, defined as dry mass of roots divided by dry mass of shoots, depends on partitioning of photosynthates ( Engels, 1994 ; Rogers

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Claudia Fassio, Ricardo Cautin, Alonso Pérez-Donoso, Claudia Bonomelli and Mónica Castro

ratio, the clonal trees (grafted and nongrafted) produced a higher root-to-shoot ratio than the seedling trees. According to Wolstenholme (1987) , the avocado tree root system is relatively inefficient, with low hydraulic conductivity and few

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Genhua Niu, Denise Rodriguez and Mengmeng Gu

did not significantly affect growth either. Therefore, the effect of N rate on shoot dry weight, root dry weight, root-to-shoot ratio, and the total dry weight were pooled from N forms ( Table 2 ). The shoot dry weight of Texas mountain laurel treated

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Hye-Ji Kim and Xinxin Li

for an optimum plant growth and the implications of such a baseline without interference with other factors. The effects of P on root growth and root-to-shoot ratio present conflicting results among the studies on container crops. According to Harris

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Bryan J. Peterson and William R. Graves

), whereas root-to-shoot ratios of eastern congeners never exceeded those of western congeners. Fig. 3. Root dry weight, shoot dry weight, root:shoot, and total leaf area of seedlings of Sambucus grown for 35 d in each of six root-zone moisture conditions

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Bryan J. Peterson and William R. Graves

plant, media were washed from the roots, and both shoots and roots were dried at 67 °C for 5 to 7 d. Roots included all biomass below the cotyledon scars. Shoots and roots were weighed, and a root-to-shoot ratio was calculated for each seedling. Leaves