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Radish Soil Growth

The Effects of Soil Restrictions on the Growth of Rapid Radish (Raphanus sativus) seedlings

Abstract

The growth of twelve Rapid Radish (Raphanus sativus) seedlings were observed from plastic soil containers to see whether soil restrictions effect the overall growth of root and shoot systems. Three different soil volumes were used; 110ml, 150ml, and 180ml, with four containers representing each soil volume. Each container that held a Rapid Radish (Raphanus sativus)seedling was given 35ml of water once a week for over the course of four weeks. All containers were held in a controlled environment growth cabinet. Observations were recorded on shoot and root weight, shoot length, root length, and length of entire plant from root to shoot. On average, the seedlings in the 180ml soil container showed the most overall growth. Soil restrictions had a significant influence on the overall growth of the plants. The average weight, shoot length, and root length of the plants in the 180ml soil volume were significantly higher than those in the 110ml or 150 ml soil volumes.

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Plants undergo many physiological and morphological changes in response to reduced rooting volume (NeSmith 1993). Plant responses to reduced soil volume have been reported for a wide range of crops with some conflicting data among them (NeSmith 1993). In real-world matters, the issue of container size and soil volume is extremely important to both transplant producers and transplant consumers. (NeSmith 1993). While the use of smaller containers may improve the efficiency of transplant production, it is unclear how plants grown in smaller root volumes will perform under post-field conditions. A major effect of decreased container size is that it increases root restricting conditions experienced by transplants (NeSmith 1993).

The hypothesis of this study is that small containers containing small soil volumes reduced the overall growth of rapid radish seedlings. In general, as container size increases plant leaf area, shoot biomass and root biomass increase (Cantliffe, 1993). Growth rates of shoots and roots are interdependent (Tonutti, 1990). The delicate balance between roots and shoots can be upset when the root system is restricted in a small rooting volume (NeSmith 1992). The resulting imbalance can have short term, as well as long term, effects on plant growth. The objective of this study is to investigate the average weight, shoot length, root length, and length of the entire plant from root to shoot of rapid radish in response to different soil volumes.

Methods and Materials

Plant Material. Twelve rapid radish seeds (Raphanus sativus) were germinated and grown in two plastic 2X3 container cells. Four cells received 110ml soil, four cells received 150ml soil, and four cells received 180ml of soil (requires extra large cells). Each container contained commercial potting mixture and each contained one seedling. The experiment was carried out in a laboratory that contained a controlled environment growth cabinet. Optimal day and night temperatures were maintained accordingly. 35ml of water was added once a week to each container for four weeks. Plants were grown for a total of 28 days.

Growth Measurements. After the 28th day of growth, plants were carefully rooted from each plant container without damaging the root system of the plant. Plants in the four cells containing 110ml of soil were carefully rooted and placed side by side to notice the overall growth in relation to each other. Pictures were taken for future reference. Using a 12-inch plastic ruler, we measured the length of each shoot from the base of the shoot to the longest above ground axis of the plant in millimeters. The same was done for the root system of the plant. Root and shoot ratios were derived using the results. The fresh weight, (after removing all the soil from the roots), of the total plant was recorded using a weight scale. Same procedure was repeated for the 150ml and 180ml soil volume containers.

Results

Plant Growth. Average shoot length of the rapid radish seedlings was significantly higher in 180ml soil container compared to 110ml and 150ml (Table 1). However, the 150ml soil volume container was significantly lower than the 110ml soil container (Table 1). As soil volume increased average root length increased (Table 2). The seedlings in the 180ml experienced the greatest increase in root length (Table 2). The entire plant weight did increase as soil volume increase for the exception of the 150ml soil container (Table 3). On average the growth of the entire plant from root to shoot did increase as soil volume increased (Table 4).

Table 1. Effects of Soil Volume on Average Shoot Length of Rapid Radish

Soil Volume (ml)Average Shoot Length (mm)

110

222.5

150

160.0

180

337.5

Table 2. Effects of Soil Volume on Average Root Length of Rapid Radish

Soil Volume (ml)Average Root Length (mm)

110

107.5

150

116.7

180

202.5

Table 3. Effects of Soil Volume on Average Plant Weight

Soil Volume (ml)Average Plant Weight (g)

110

2.45

150

1.33

180

2.68

Table 4. Effects of Soil Volume on Growth of Entire Plant (Average)

Soil Volume (ml)Length of Entire Plant (mm)

110

330.0

150

276.7

180

540.0

Discussion

Rapid radish plants respond to conditions which restrict root growth by limiting both root and shoot growth. Other studies have indicated that restricting root development under otherwise favorable environmental conditions resulted in dwarf plants which had reduced leaf area and shoot dry weight (Tonutti, 1990). Our results represent a flaw to that correlation. 180ml of soil volume did experience the most overall growth in each trend, but seedlings planted in the 150ml soil volume experienced less overall growth than 110ml on overall shoot length, plant weight, and entire plant average. This outcome is strange to me since 110ml should have experienced the least overall growth. However, average root length did experience a “normal” correlation of 110ml<150ml<180ml (Table 2). The 150ml soil volume didn't experience the expected results due to factors affecting the seedling's growth. Possible factors could be inadequate soil nutrients, composition of the seedlings, or inadequate light intensity.

Literature Cited

Journal article: Cantliffe, D.J. 1993. Pre- and postharvest practices for improved vegetable transplant quality. The American Society for Horticulture Science.3: 415-417.

Journal article: NeSmith, D.S., D.C. Bridges, and J.C. Barbour. 1992. Bell Pepper Response to Root Restriction.Journal of Plant Nutrition 15: 2763-2776.

Journal article: NeSmith, D.S. 1993a. Influence of root restriction on two cultivars of summer squash (Cucurbita pepo L.). Journal of Plant Nutrition. 16: 421-431.

Journal article: NeSmith, D.S. 1993b. Summer squash response to root restriction under different light regimes. Journal of Plant Nutrition. 16: 765-780.

Journal article: Tonutti, P. and C. Giulivo. 1990. Effect of available soil volume on growth of young kiwi plants. Acta Horticulturae. 282: 283-294.

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