Effect of interactions between carbon dioxide enrichment and NH/NO ratio on pH of culturing nutrient solution, growth and vigor of tomato root system

Abstract

A growth chamber experiment was conducted to investigate the influence of NH₄⁺/NO₃^- ratio and elevated CO₂ concentration on the pH in nutrient solution, growth and root vigor system of tomato seedling roots, which attempts to understand whether the elevated CO₂ concentration can alleviate the harmful effects of higher NH₄⁺–N concentration in nutrient solutions on the tomato root system. Tomato (Lycopersicon esculentum Mill. var. Hezuo 906) was grown in pots with nutrient solutions varying in NH₄⁺/NO₃^- ratio (0:1, 1:3, 1:1, 3:1 and 1:0) and the growth chambers were supplied with ambient (360 ?L·L^-1) or elevated CO₂ concentration (720 ?L·L^-1). The results showed that the pH changed with the growth process and CO₂ concentration increased. At both CO₂ levels, pH increased when 100% NO₃^-–N was supplied and decreased in other treatments. The pH decrease in the nutrient solution was directly correlated to the NH₄⁺-N proportion. The pH value was more reduced in 100% NH₄⁺–N nutrient solution than increased in the 100% NO₃^-–N nutrient solution. CO₂ enrichment increased the dry weight of shoots and roots, root vigor system, total absorbing area and active absorbing area of tomato seedlings. All the measurement indexes above were increased in the elevated CO₂ concentration treatment with the NO₃^- proportion increase in the nutrient solutions. Thus, under the elevated CO₂ concentration, the dry weights of shoots and roots, root vigor system, total root absorbing area and active absorbing area were found to be inversely correlated to NH₄⁺/NO₃^- ratio, leading to about 65.8%, 78.0%, 18.9%, 12.9% and 18.9% increase, respectively, compared with that under the ambient CO₂ concentration. Our results indicated that tomato seedling roots may benefit mostly from CO₂ enrichment when 100% NO₃^-–N nutrient solutions was supplied, but the CO₂ concentration elevation did not alleviate the harmful effects when 100% NH₄⁺–N was supplied.

References

1. Brouwer R (1983). Functional equilibrium: sense or nonsense? Netherlands.J Agric Sci, 31: 335–348
2. Cramer M D, Lewis O A M (1993). The influenceof NO₃^- and NH₄⁺ nutrition on the carbonand nitrogen partitioning characteristics of wheat (Triticum aestivum L.) and maize (Zea mays L.) plants.Plant Soil, 154: 289–300. doi:10.1007/BF00012534
3. Faculty of Plant Physiology,Department of Biology East China Normal University. (1988). Experimental Guide of Plant Physiology. Beijing: Higher Education Press (in Chinese)
4. Findenegg G R (1987). A comparative study of ammonium toxicity at differentconstant pH of the nutrient solution. PlantSoil, 103: 239–244. doi:10.1007/BF02370395
5. Gao J F (2000). Experimental Techniques of Plant Physiology. Xi'an: WorldBooks Publishing Company (in Chinese)
6. Li J, Zhou J M, Duan Z Q, Du C W, Wang H Y (2005a). Effects of the interactionsof carbon dioxide and nutrients on tomato seedlings. Acta Bot Boreali-occident Sin, 25(10): 2112–2117 (in Chinese)
7. Li J, Zhou J M, Duan Z Q, Du C W, Wang H Y (2005b). The effect of theinteractions between nutrient supplying intensity and carbon dioxideenrichment on the growth and some physiological indexes of tomato. Acta Agriculturae Boreali-occidentalis Sinica, 14(4): 10–13 (in Chinese)
8. McConnaughay K D M, Coleman J S (1999). Biomassallocation in plants: ontogeny or optimality? A test along three resourcegradients.Ecology, 80: 2581–2593
9. Mehrer I, Mohr H (1989). Ammoniumtoxicity: Description of the syndrome in Sinapisalba and the search for its causation. Physiol Plant, 77: 545–554. doi:10.1111/j.1399‐3054.1989.tb05390.x
10. Olsthoorn A F M, Keltjens W G, Van Baren B, Hopman M C G (1991). Influence of ammonium on fine root development and rhizospherepH of Douglas-fir seedling in sand. Plantand Soil, 133: 75–81. doi:10.1007/BF00011901
11. Reynolds J F, Thornley J H M (1982). A shoot:root partitioning model. Annals of Botany, 49: 585–597
12. Troelstra S R, Wagenaar R, Smant W (1995). Nitrogen utilization by plant speciesfrom acid heathland soils: I. Comparison between nitrate and ammoniumnutrition at constant low pH.J Exp Bot, 46: 1103–1112. doi:10.1093/jxb/46.9.1103
13. Wei M, Xing Y X, Ma H, Wang X F, Li B (2000). Effects of CO₂ enrichment in raising vigorous seedlings of fruited vegetable. Journal of Shandong Agricultural University (NaturalScience), 31(2): 196–200 (in Chinese)
14. Wilson J B (1988). A review of evidence on the control of shoot: root ratio,in relation to models. Annals of Botany, 61: 433–449
15. Xu D Q (1994). Responses of photosynthesis and related processes tolong-term high CO₂ concentration. Plant Physiology Communications, 30(2): 81–87 (in Chinese)
16. Yang H J, Yang L X, Liu H J, Huang J H, Dong G C, Zhu J G, Wang Y L (2006). Effectof free-air CO₂ enrichment on root activityof Japonica rice (Oryza sativa L.)cultivar Wuxiangjing 14.Acta Agronomica Sinica, 32(1): 118–124 (in Chinese)
17. Zhang F C, Kang S Z, Ma Q L (1999). The effects of the atmospheric CO₂ concentration increase on physiological charactersand growth of cotton. Journal of BasicScience and Engineering, 7(3): 267–272 (in Chinese)
18. Zhang F S (1998). Environmental Stress and Rhizosphere Nutrition. Beijing: China Agricultural Press (in Chinese)