General principles of plant nutrient deficiency
Tomatoes in nutrient deficiency experiments
Background on the nutrients used
The 2014 plant appearance results
Problems in 2014
Some Remarks about Your Paper
In 2014, you are testing 3 null hypotheses about plant biomass and 3 null hypotheses about leaf blade SCC. In each case, these are that the dependent variable (biomass or SCC) is the same in control plants and in either nitrogen-deficient plants, phosphorus-deficient plants, or plants grown in distilled water after 4 weeks of growth. It would be possible to reject some of the 6 nulls and to fail to reject others. Several of the nutrient deficiencies are supposed to cause stunting of the plant, but the information below discloses that not all of them are supposed to cause a decrease in SCC. In some cases an increase in SCC is expected, at least in young leaves, because the deficiency hurts leaf growth more than it hurts chlorophyll production. This gives small, intensely green leaves. Therefore, read the background and make intelligent predictions about the effect of nutrient deficiency on both biomass and SCC.
This Web site does not present numerical results. These results are available in spreadsheet form at the bottom of this site, and it is up to you to do the statistical analysis using the chi-square median test (also downloadable from this site). There are several ways to present the data; you make
decision, but remember the guidelines you were given in Biology 1100
which are also given in Appendix II of your lab manual).
The remainder of this section will be background information on the specific nutrient deficiencies we used. I cite published literature, but more background on nutrient deficiencies in tomatoes can be seen on:
Taiz and Zeiger, a recent plant physiology book.
University of Massachusetts at Amherst, which has a Web site for an
organic gardening course that shows pictures (very small pictures, unfortunately) of some tomato nutrient
Tomatoes suffering from nitrogen deficiency tend to be rigidly upright, with hard, thin stems and small leaves. Leaves are yellowish and then wither. Flowers fall prematurely (Bergmann, 1992, p. 90).
Figure 2. Early nitrogen deficiency in tomato. Note chlorosis that is more intense between the veins than along the veins (Bergmann, 1992, p. 392).
Bergmann (1992, p. 103) reported that typical symptoms of phosphorus deficiencies in tomatoes include stunting, dark green young leaves and yellowing older leaves, curled leaflets, thin stems with purple coloring, and poor fruit production. Tomatoes are sensitive to lack of phosphorus.
Figure 4. Left: Tomato with phosphorus deficiency. About the only symptom apparent here is the thin stem that could not support the plant (Roorda van Eysinga and Smilde, 1981, p. 12). Right: Deposition of purple pigment in -P leaves on 2 April 2010. We only saw hints of this purple pigment in the distilled water plants this year.
Iron is an immobile element in plants because it is held in insoluble forms such as iron oxides and an iron-protein complex called phytoferritin, which is stored in chloroplasts. It is difficult for these insoluble molecules to enter the phloem for transport. Therefore, when iron deficiency strikes, the newer leaves tend to suffer first, becoming chlorotic. This starts in the areas between the veins, and then may involve the whole leaf as chlorophyll synthesis in the new leaf is disabled (Salisbury and Ross, 1992, p. 132). Because of its role in respiration, iron-deficient plants have lowered metabolic rates.
Figure 5. Iron-deficient tomato with characteristic chlorosis on newest leaves, especially between the veins (Bergmann, 1992, p. 552).
While we might think that plants grown in distilled water would have all the nutrient deficiency symptoms above, our results seem to show that distilled water mostly produces the symptoms of nitrogen deficiency, stunting and chlorosis of the leaves. This emphasizes the important role that nitrogen plays in plant growth. It also shows how nutrient deficiencies could interact. If the plant cannot grow without nitrogen, its need for the other nutrients is so reduced that it doesn't show their deficiency symptoms. The distilled water plants also had a tendency toward purple leaf veins, a phosphorus deficiency symptom. The -N plants did not have purple veins and were not quite as chlorotic as the distilled sater plants.
Figure 6 shows a comparison of the distilled water and -N tanks in 2009. Figure 7 shows a comparison of the complete and distilled water leaves, showing the purple veins in the latter.
Figure 6. The distilled sater treatment (left) compared with the -N treatment (right) on 30 March 2009. The Distilled Water plants looked worse and had purple pigment deposited along their leaf veins.
Figure 7. A Complete leaf and a distilled water leaf on 8 April 2009. Note the intense chlorosis and purple veins of the distilled water leaf.
The 2014 tomatoes were planted from 11-13 March 2014, and were harvested from 8-10 April. This is the third year we used hydroponic recirculators, but this year we grouped together all the completes, all the -N, all the -P, and all the distilled water plants to make photography easier. You should note that this might have caused bias because if something was wrong with one set of lights, for example, all the bad effects would afflict one treatment.
Figure 8. The distilled water recirculators on March 14, 2014. All the treatments looked similar to this and were healthy.
Figure 9. By March 26, the complete plants (left) were markedly taller than the -N plants (right). The -N leaves also seemed paler than the complete leaves.
Figure 10. The complete plants on March 26 were robust and the picture of tomato health.
Figure 11. The complete plants (left) vs. the -N plants (right) on April 4. This was the best the completes looked because after this they got so big that they started to topple over. You can also see the thin but tall -P plants towering over the -N plants on the other side of the lab bench.
Figure 12. The pale and spindly distilled water plants were dwarfed by the complete plants (other side of the lab bench) on April 4.
Figure 13. By April 7 (Monday of harvest week), The completes were very big and green, but toppling over, with some branches broken and wilting. Those little cups were never meant to hold a plant that big.
Figure 14. On April 7, the -N plants were slightly chlorotic and dwarfed by both the completes (upper left) and -P plants (upper right, on other side of the lab bench).
Figure 15.The sharp contrast between a complete leaf (dark green) and some chlorotic -N leaves on April 7.
Fig. 16. The tall but thin -P plants contrasted with the dwarfed distilled water plants beyond them on April 7.
Fig. 17.Widespread necrotic spots on the - P plants on April 7.
Fig. 18. The distilled water plants on April 7 were small, chlorotic, and had some veins that had turned purple.
Fig. 19. A distilled water leaf compared with a complete leaf on April 7. The slight purple color on the distilled water leaf vein indicates phosphorus deficiency. This symptom was not obvious on the -N leaves, and was only seen to a slight extent on the distilled water leaves.
The big problem was that apparently on Tuesday of the harvest week, students trying to extract their complete plants pulled the hoses off the pumps in two of the complete recirculators. This caused the upper recirculator compartment (with the roots) to run dry. This meant that 2/3 of the complete plants were dying of dehydration by the time they were harvested. However, the weights and the SCCs did not seem to be affected, so Dr. Kosinski left all these plants in the data.
Aside from this, the experiment in 2014 had mixed results. We started the experiment with unusually big plants. This might have allowed the plants to recycle nutrients and avoid most deficiency symptoms. The effects of lack of N (seen in the -N and Distilled Water treatments) on growth were very marked. There were not such marked effects of P deficiency (although the results might still be statistically significant). The effects on SCC were more subtle, although the means seemed to vary in the expected way, with Completes highest and -N and Distilled water low. Some SCC results might be significant. You will find out when you analyze the data.
Another problem that has bedeviled this experiment for years is variability between the plants in the same treatment. The picture below shows two contrasting Complete plants in 2003.
...is on a results spreadsheet that must be downloaded. This has the initial results on the sheet 1 and the final results on sheet 2. The chi-square median test spreadsheet and a spreadsheet of test data can also be downloaded. The test data will allow you to be assured that you are using the median test correctly. Finally, there is a set of directions on how to use the median test spreadsheet.
Good luck with your plant nutrient report. It must be uploaded by11:59 PM on April 24, 2014.
Bergmann, W. 1992. Nutritional Disorders of Plants: Development, Visual and Analytical Diagnosis. Gustav Fischer Verlag, New York.