Becky Conway Biology 1615 Lab

ROOT SYSTEM ARCHITECTURE OF KOSTELETZKYA PENTACARPOS (MALVACEAE) AND BELOWGROUND ENVIRONMENTAL INFLUENCES ON ROOT AND AERIAL GROWTH DYNAMICS

1. 
   Introduction
   
   1. 
      Changes in global climate including rising temperatures and sea levels along with increases in the world population have put strains on the earths’ natural resources.
      

2. At the same time, rising sea levels are taking away some of the arable land traditionally used for food production.

2. 
   A crop that could be grown in areas where normal food and bio fuel crops won’t grow would provide multiple resources for solving several global economic issues.
   

2. K. pentacarpos is a salt tolerant crop so can be grown in coastal areas where sea level and dredging have made it impossible to grow other bio fuel or food crops.

3. 
   Many studies have already been done on K. pentacarpos including salt tolerance, seed germination, and water-use efficiency among others. In this study, the objective was to gain further insight into the domestication of this plant as a bio fuel crop and transitional coastal plant by:
   
   1. 
      determining the effect of soil composition and nutrient availability on root system growth and plant function;
      
   2. 
      determining quantity of newly produced root biomass during the growing season;
      
   3. 
      quantify the total non-structural carbohydrates stored by 2-yr old plants;
      
   4. 
      document the mass, surface area, and length of 2-yr old field-grown plants.
      

2. 
   Materials and Methods
   
   1. 
      45 samples of K. pentacarpos in PVC pipes were taken from a commercial farm near Lewes, Delaware.
      

2. Four treatment groups were grown in the light in a greenhouse, one was grown in dark.

3. Groups were as follows: 1) Control-grown in native Sassafras sandy loam soil with no amendments; 2) dredge spoil material from a recent dredging of the Lewes-Rehoboth Canal; 3) Sassafras sandy loam with a small addition of nutrients; 4) Sassafras sandy loam soil with a high addition of nutrients. The group grown in the dark were grown in the native Sassafras sandy loam with no amendments.

4. All other growing conditions such as light and temperature we maintained consistent across the groups except for the one group grown in the dark.

2. 
   Plants were grown from a period of March through October.
   

2. Aerial biomass was measured and sorted as to type: stems, leaves, flowers, and seed capsules.

3. 
   Root morphology was measured by taking three samples of field grown plants. These samples were laid out, cleaned and allowed to dry. Each sample was divided into fifteen sections which were photographed, analysed, and root samples counted and measured by sections which represented soil depths.
   

3. 
   Results
   
   1. 
      Total coarse root biomass was significantly affected by the soil treatment with the high nutrient group having more than any other group. Ratio of fine root mass to coarse root mass was highest in the control group.
      
   2. 
      Aerial growth of the plants also was greatest during both growth cycles in the high nutrient group, with the dredge group being the lowest among the groups grown in the light. The group grown in the dark had only one growth period and the lowest biomass.
      
   3. 
      Allocation of resources varied between the two growth periods. Although the total biomass increased with the addition of nutrients, the percentage of biomass allocated to reproductive growth was constant as a percentage across all groups.
      

4. 
   Discussion
   
   1. 
      In answering the question of what the effects of growing K. pentacarpos in dredged material would have, there were mixed results. The number of stems produced and the root biomass was not significantly different between the control and the dredge group. The root to shoot ratios were also not statistically different.
      
   2. 
      Addition of nutrients increased the production of overall biomass including seed capsules which is important for the production of bio fuel.
      
   3. 
      The majority of both coarse and fine roots were located within the top 20 cm of soil. The distribution of roots affects the ability of a plant to access water and nutrients and also to provide for stability of the plant. The root systems also contribute to the stability of the surrounding soils. Growth of K. pentacarpos will contribute to the stabilization of the surrounding soil due to the large quantities of fine roots produced.
      
   4. 
      The growth response of K. pentacarpos to differing soil types and nutrient conditions as well as its root architecture make it a promising plant for further development as a bio fuel crop in otherwise unusable saline coastal land. The results show that this plant can produce adequately in soil dredged from salt water, and can contribute to stabilizing this soil from coastal erosion forces.
      
   5. 
      Some of the limitations of the study included:
      

1. 
   Not being able to harvest the total root biomass from the samples taken in the field. This resulted in lower measured masses compared to other plants.
   
2. 
   Growing the plants in a greenhouse caused them to go through two growth cycles compared to just one in the field. This could have been due to the signalling of warmer temperatures earlier than normal, to different day length signals, or the accumulation of heat units. Although this could affect the results compared to field grown units, the conditions were consistent across the groups for the affects being studied (i.e. soil conditions and nutrient availability). There was also not a measured difference in growth between the study groups and field grown groups during the second growth period.