Nutrient Deficiencies in Tomatoes

by Robert Kosinski
Clemson University
rjksn@clemson.edu

Your paper
General principles of plant nutrient deficiency
Tomatoes in nutrient deficiency experiments
Background on the nutrients used
The 2014 plant appearance results
Problems in 2014
Literature Cited


Some Remarks about Your Paper

Before beginning, in previous years, we used a -Fe (iron) treatment in this experiment, and we may use it again in future years. Therefore, I have left in all the references to iron because it would be a lot of work to take them out and them put them back again. Just be aware that there was no -Fe treatment this year.

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 the decision, but remember the guidelines you were given in Biology 1100 (and which are also given in Appendix II of your lab manual).
 

Nutrient Deficiencies in Plants...General Principles

Nutrient deficiencies can produce several effects: stunted growth, chlorosis (yellowing), and necrosis (death) of certain plant parts. In lecture we talked about a general feature of nutrient deficiencies. Plants can withdraw an element from older tissue and send it to newer tissue, so if a mobile element is lacking, the symptoms will appear on older foliage first (Salisbury and Ross, 1992, p. 129). That is, new leaves will look green and healthy while older leaves may be yellow and drooping, or even dead. On the other hand, if the deficient element is immobile, the effects will show up first in new foliage. In our experiment, N and P were considered mobile elements. Fe (used in other years) was considered immobile. Chlorosis of new foliage (but not old foliage) on some of the -Fe plants was seen in 2010 and 2011, but not very often in 2012 or 2013.

Stunted

Figure 1. A stunted, chlorotic, -Fe tomato on April 7, 2003. The old leaves are green and the new leaves are bright yellow. Iron is an immobile element.
 

Tomatoes in Nutrient Deficiency Experiments

Tomatoes (Lycopersicon esculentum) are a good choice for nutrient deficiency experiments because they are easily grown in the lab and produce obvious symptoms of nutrient deficiency on their leaves. Each growth stage of tomato has its own nutrient requirements; our young tomatoes (40-70 days old while we were growing them) were in the stage called vegetative growth, prior to flowering and fruit set. During this stage, tomato increase in mass is mainly in the leaves. In contrast, at harvest, about 3/4 of tomato biomass is in the fruit (Wilcox, 1994). Tomatoes are known as a "hungry" crop that requires large amounts of nutrients, especially phosphorus.

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.

The 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 deficiency symptoms.

The Nutrient Deficiencies Used

Nitrogen

Although nitrogen gas is abundant in the atmosphere, nitrogen is the element that is most commonly deficient in soils because only fixed nitrogen (nitrate or ammonium) is useable by plants. Nitrogen makes up about 1-5% of plant dry weight (Bergmann, 1992, p. 86), and has so many roles in proteins, nucleic acids, and many other macromolecules that the primary effect of nitrogen deficiency is stunted growth. Because nitrogen is necessary for chlorophyll formation but can be easily moved in the plant, another obvious symptom is yellowing of older leaves (Salisbury and Ross, 1992, p. 130; Bennett, 1994; ). Nitrogen deficiency tends to retard vegetative growth and accelerate flowering, although yields of fruit are reduced over the case where nitrogen is adequate. One reason for this is that nitrogen deficiency also has hormonal effects on the plant, retarding cytokinin synthesis and accelerating synthesis of abscisic acid, the "hormone of stress and dormancy." This ages the plant rapidly and reduces its lifespan (Bergmann, 1992, p. 88).

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).

Tomato-N

Figure 2. Early nitrogen deficiency in tomato. Note chlorosis that is more intense between the veins than along the veins (Bergmann, 1992, p. 392).

Chlorosis  YellowLeaf

Figure 3. Left: the same interveinal chlorosis in our -N tomatoes on April 7, 2003. Right: Chlorotic -N leaves compared with a "Complete" leaf, 12 April 2005.

Phosphorus

Phosphorus is the second most common limiting nutrient in soils. It is both taken up and used as phosphate ion. Perhaps the most important structural use of phosphorus is in phospholipids in membranes. Phosphorus also has many other hereditary and metabolic roles (in DNA and RNA, ATP, NADP, etc.), and so lack of phosphorus hampers cell reproduction, inheritance, and normal metabolism. The result is general stunting (Salisbury and Ross, 1992, p. 131; Bennett, 1994). Some plants without any phosphorus input can "recycle" phosphorus from organic molecules for amazingly long periods; Bergmann (1992, p. 98) cited an 1882 report that an oak tree kept in phosphorus-free medium was able to survive for three years with no growth, but then finally died. Perhaps because of this recycling, respiration rates tend to be higher in phosphorus-deficient plants. Phosphorus deficiency retards leaf growth, but not chlorophyll synthesis, so leaves of phosphorus-deficient plants tend to be darker green than leaves of control plants, and this may make them look healthier. Bergmann (1992, p. 98) remarked that phosphorus deficiency is nearly impossible to spot in the field unless control plants without phosphorus deficiency are available for comparison. Phosphorus-deficient leaves can also have a deposition of purple anthocyanin pigment on their undersides.

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.

Tomato-PPix/Purple Leaf

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

Iron is our only micronutrient, and a largely immobile element. Therefore, it must be taken up continuously. Iron is part of certain proteins and enzymes that participate in electron transport (especially the cytochromes). Its role here is very important, because it is often iron itself that accepts and releases electrons, changing between the Fe+3 to Fe+2 states as it does so (Salisbury and Ross, 1992, p. 132). Iron is also necessary for chlorophyll synthesis and protein synthesis (Bennett, 1994).

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.

Tomato-Fe

Figure 5. Iron-deficient tomato with characteristic chlorosis on newest leaves, especially between the veins (Bergmann, 1992, p. 552). 

Distilled Water

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.

H2O-N Comparison   

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.

Complete vs H20 Leaves

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 Visual Results

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.

Distilled water 3-14-14


Figure 8. The distilled water recirculators on March 14, 2014. All the treatments looked similar to this and were healthy.


Com vs. -N 3-14-14

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.

Com 3-26-14

Figure 10. The complete plants on March 26 were robust and the picture of tomato health.Com vs. -N 4-4-14

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.

Dis vs. Com 4-4-14

Figure 12. The pale and spindly distilled water plants were dwarfed by the complete plants (other side of the lab bench) on April 4.

Com 4-7-14

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.

-N 4-7-14

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).


-N Leaves 4-7-14
Figure 15.The sharp contrast between a complete leaf (dark green) and some chlorotic -N leaves on April 7.

-P 4-7-14

Fig. 16. The tall but thin -P plants contrasted with the dwarfed distilled water plants beyond them on April 7.

 

-P Nec 4-7-14

Fig. 17.Widespread necrotic spots on the - P plants on April 7.

Dis 4-7-14

Fig. 18. The distilled water plants on April 7 were small, chlorotic, and had some veins that had turned purple.

Dis Leaf 4-7-14

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.

 

Problems in 2014

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.

Monster Midget
Fig. 18. Control plants if very different sizes held by students Jennifer Zurosky and Omar Ladhani in 2003. Note the root mass of the plant being held by Omar.


This variability can cause a chi-square test to declare a non-significant result. For example, say that the -N treatment is obviously smaller than the Complete treatment, but both treatments have a few big plants and lots of small ones. The reason the Complete treatment looks more impressive is because its "big" plants dwarf the bigger plants in the -N treatment. However, the chi-square median test makes its decisions based on the numbers of plants in each treatment above and below the median of the combined data set. If the median of that data set (Completes plus -N here) is 15 g, a plant that is 16 g in -N and a plant that is 160 g in the Complete treatment are considered to be the same--they are both above the median, and that's all. How far above the median those big Complete plants are would not matter.

This brings up a general principle of statistics. In order to declare a significant difference, we must have a difference between the means, but we also must have small variability within each treatment. The variability within each treatment often prevented a significant difference from being declared in the past.
You will have to determine whether that is true this year as well.

 

The 2014 Data

...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.

Literature Cited

Bennett, W. F. 1994. Plant nutrient utilization and diagnostic plant symptoms. Pp. 1-7 in W. F. Bennett (Ed.), Nutrient Deficiencies and Toxicities in Crop Plants. APS Press, St. Paul, MN.

Bergmann, W. 1992. Nutritional Disorders of Plants: Development, Visual and Analytical Diagnosis. Gustav Fischer Verlag, New York.

Roorda van Eysinga, J. P. and K. W. Smilde. 1981. Nutritonal Disorders in Glasshouse Tomatoes, Cucumbers and Lettuce. Centre for Agricultural Publishing and Documentation, Wageningen, the Netherlands.

Salisbury, F. B. and C. W. Ross. 1992. Plant Physiology, 4th Ed. Wadsworth Pub. Co., Belmont, CA.

Wilcox, G. E. 1994. Tomato. Pp. 137-141 in Bennett, W. F. Nutrient Deficiencies and Toxicities in Crop Plants. APS Press, St. Paul, MN.