Ammonia–Nitrate Mixture Dominated by NH4+–N Promoted Growth, Photosynthesis and Nutrient Accumulation in Pecan (Carya illinoinensis)

Mengyun Chen,Junping Liu,Fangren Peng,Kaikai Zhu,Pengpeng Tan,Junyi Xie,Guolin Chu,Xiuwen Yao

doi:10.3390/f12121808

Abstract

Although ammonia–nitrogen (NH4+–N) and nitrate–nitrogen (NO3−–N) are the two main forms of N absorbed and utilized by plants, the preferences of plants for these forms are still unclear. In this study, we analyzed the growth, photosynthesis, and nutrients of pecan under different NH4+:NO3− ratios (0/0, 0/100, 25/75, 50/50, 75/25, 100/0) by indoor aerosol incubation. The results showed that additions of different N forms promoted the growth and development of pecan seedlings. When NO3−–N was used as the sole N source, it significantly promoted the ground diameter growth of pecan and increased the leaf pigment content and photosynthetic rate. The NH4+:NO3− ratio of 75:25 and NH4+–N as the sole N source significantly increased the soluble sugars in stems and roots, starch in leaves, stems and roots, soluble protein in leaves and stems, and soluble phenols in stems and roots. Additionally, the NH4+:NO3− ratio of 75:25 increased plant height, leaf number, root soluble protein, and leaf soluble phenol contents. In conclusion, regarding the physiological aspects of pecan growth, pecans are more inclined to use NH4+–N. Considering that the NH4+–N as the only N source may lead to nutrient imbalance or even toxicity, the NH4+:NO3− ratio of 75:25 was most favorable for the growth and development of pecan seedlings.

Highlights

Nitrogen (N) is a nutrient that plays a key role in plant growth and development, and ammonia–nitrogen (NH4 + –N) and nitrate–nitrogen (NO3 − –N) are the two main N forms absorbed and utilized by plants [1]
Time had extremely significant effects on the growth indicators of the pecan seedlings (p < 0.01), while the NH4 + :NO3 − ratios of the nutrient solution only showed a significant impact on the height and ground diameter of the seedlings (p < 0.01)
T4 significantly increased the relative increase in pecan seedling height (p < 0.05) (Figure 1B), and the other NH4 + :NO3 − treatments increased this parameter to a certain extent, but there was no significant difference from CK

Summary

Introduction

Nitrogen (N) is a nutrient that plays a key role in plant growth and development, and ammonia–nitrogen (NH4 + –N) and nitrate–nitrogen (NO3 − –N) are the two main N forms absorbed and utilized by plants [1]. Different plants have different preferences for the uptake of NH4 + and NO3 −. N forms are present, plants preferentially use one of them [5,6]. The N concentration directly affects the plant uptake of N, and concentrations either too high or too low may limit the uptake of N [8]. Temperature affects plant N uptake mainly by altering plant metabolic processes, with high temperature promoting N absorption [9] and low temperatures inhibiting N accumulation [10]. The pH affects the proportion of NH4 + and NO3 − entering the plant [11]. Plants adapted to growth in acidic soil prefer NH4 + and have significantly higher rates of nutritional and, especially, reproductive growth; in contrast, plants adapted to high pH calcareous soil preferentially

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Discussion

Conclusion