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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Rangeland Resources & Systems Research » Research » Publications at this Location » Publication #323065
Title: Interactive effects between nitrogen fertilization and elevated CO2 on growth and gas exchange of papaya seedling

Author
item CRUZ, JAILSON - Embrapa
item ALVES, ALFREDO - Embrapa
item Lecain, Daniel
item Ellis, David
item MORGAN, JACK - Retired ARS Employee

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2015
Publication Date: 2/22/2016
Citation: Cruz, J.L., Alves, A.A., Ellis, D.D., Morgan, J. 2016. Interactive effects between nitrogen fertilization and elevated CO2 on growth and gas exchange of papaya seedling. Scientia Horticulturae. 202:32-40.

Interpretive Summary: Papaya is an economically cultivated fruit crop, popular in tropical and subtropical regions. It is ranked first on nutritional scores among 38 common fruits, based on the percentage of the United States Recommended Daily Allowance for vitamin mineral and fiber, and for fighting to several diseases. Various aspects of the production system, such as mineral deficiency, establishment of seedlings, drought, among others, have prevented the papaya from reaching appropriate yields in some regions of the world. Today, ambient carbon dioxide (CO2) concentrations are approximately 400 parts per million, and are projected to exceed 800 parts per million by the year 2100. As plants can be strongly affected by CO2, there is tremendous interest to understand how these increasing levels of CO2 might affect plant growth and agricultural production. Responses of plants to CO2 are known to be influenced by nitrogen (N). Plants cultivated under elevated CO2 concentration require more nutrients, especially N, to sustain the increased. Papaya plants are consequently very sensitive to soil N deficiency. The aim of this study was to evaluate the effect of the elevated CO2 level and its interaction with N on the growth, gas exchange, and nitrogen-use efficiency of papaya seedlings. Our study showed that Papaya seedlings were very sensitive to both elevated CO2 and soil nitrogen nutrition. Low available soil N strongly stunted growth in papaya seedlings. However elevated CO2 alleviated this negative effect by greatly improving nitrogen-use-efficiency and plant photosynthesis rate. The combination of elevated CO2 and non-limiting soil N resulted in significantly higher growth rate in papaya. For one perspective increasing atmospheric CO2 may improve papaya production in regions with poor soil nutrients, potentially improving yields in third world countries.

Technical Abstract: Elevation of CO2 in the atmosphere will change requirements for minerals, mainly nitrogen, altering the relationship between nutrients demand and growth of the plants. We evaluated the interacting effects between CO2 concentrations (390 or 750 µL L-1) and nitrogen levels (3mM or 8mM) on the growth, nitrogen use efficiency (NUE) and gas exchange responses of papaya seedlings. Papaya was grown in 3.5-L pots in a greenhouse, with six replicates, by 62 days. Nitrogen (N) and CO2 treatments had no significant effects on stomatal conductance and transpiration. However, increase in the CO2 concentration enabled the plants to achieve a higher photosynyhesis (A), even when grown under conditions of low N. Within the same N level, leaves grown under elevated CO2 showed the highest instantaneous water-use efficiency (WUEi). Nitrogen concentration for all the organs was lower for plants grown under higher concentrations of CO2, regardless of the N level used; but, NUEs were highest for plants grown under elevated CO2. Total dry mass accumulation increased due to CO2 elevation, with the intensity of the response being higher for plants grown under lower N. In conclusion, was observed that papaya seedling grown under elevated CO2 and low N maintained A, leaf N concentration, and NUE, and increased the leaf area response. All these results, taken together, can be contributed to that low N get over the positive effect of high N on dry matter accumulation of papaya plants cultivated under elevated CO2.