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Optimal NH 4 + /NO 3 − ratios enhance the shade tolerance of soybean seedlings under low light conditions
Author(s) -
Raza A.,
Asghar M. A.,
Hussain S.,
Bin C.,
Shafiq I.,
Ahmad I.,
Ghafoor A.,
Karim H.,
Iqbal T.,
Yang W.,
Weiguo L.
Publication year - 2021
Publication title -
plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 1435-8603
DOI - 10.1111/plb.13219
Subject(s) - photosynthesis , shading , biology , light intensity , chlorophyll , photosynthetic pigment , horticulture , botany , art , physics , optics , visual arts
Abstract In the maize–soybean intercropping system, shade is the major chronic restraint that affects normal growth of soybean. Different spatial patterns of this system affect the microclimate of soybean through shading from maize plants. However, the negative impacts of shading stress can be mitigated by providing optimal ratios of different fertilizers. Therefore, to test this hypothesis, soybean plants were grown under different light conditions (normal light or shade) to evaluate the response to varying NH 4 + /NO 3 − ratios. Seeds of soybean ( Glycine max L. cv. Nan‐99‐6) were grown in nutrient solution with a total concentration of 5 mM N using different NH 4 + /NO 3 − ratios (T 0 = 0:0, T 1 = 0:100, T 2 = 25:75, T 3 = 50:50 and T 4 = 75:25) for 40 days in a greenhouse at PPFD 320.95 μmol m −2 s −1 (low light) or 967.53 μmol m −2 s −1 (normal light). Under low light, growth and photosynthesis of soybean seedlings significantly decreased as compared to normal light conditions. However, the optimal ratios of NH 4 + / NO 3 − improved growth and photosynthesis of soybean seedlings under both light conditions. Our results indicated that soybean seedlings supplied with optimal NH 4 + /NO 3 − ratios (25:75 and 50:50) have maximum biomass yield, chlorophyll pigments, leaf gas exchange, photochemical activity and root growth as compared to low and high NH 4 + /NO 3 − ratios (T 1 and T 4 ). High ratios of NH 4 + /NO 3 − (T 4 ) resulted in reduced plant growth due to nutrient accumulation in plant tissues; therefore, we suggest that optimal ratios of NH 4 + /NO 3 − (T 2 and T 3 ) can enhance the shade tolerance of soybean seedlings.