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Malus hupehensis(Pamp.) Rehd. is a widely cultivated rootstock in China. We studied the effect of three NO3-/NH4+ ratios(100/0, 50/50, and 0/100, molar basis) at total nitrogen(N) concentration of 8 mmo L L-1 in a nutrient solution on M. hupehensis seedlings. Plant biomass, NO3-and NH4+ concentration, chlorophyll content, respiratory rate, and cellular structure were investigated. M. hupehensis seedlings at the NO3-/NH4+ ratio of50/50 had the highest level of fresh weight, dry weight,shoot length, and chlorophyll(a, b, and a+b) content, but the lowest respiration rate in the leaves and roots. In addition, thickness and numbers of palisade and spongy tissue cells of the leaves were greater with this treatment than with other treatments. At the NO3-/NH4+ ratio of100/0, the leaves and roots had higher NO3-concentration and lower NH4+ concentration. However, the opposite trend occurred at the NO3-/NH4+ ratio of 0/100. Chlorophyll(a, b, and a+b) content was lowest at the NO3-/NH4+ ratio of 100/0 than at the other ratios. At the NO3-/NH4+ ratio of 0/100, oxygen(O2) consumption increased in the leaves and roots, and irregular epidermis and cortex cells were observed in the root apical meristematic and mature region. Our results indicated that the NO3-/NH4+ ratio at 50/50 was suitable for growth of M. hupehensis seedling to achieve the highest biomass production and efficiency.
We studied the effect of three NO3- / NH4 + ratios (100/0, 50/50, and 0/100, molar basis) at total nitrogen (N) concentration of 8 mmo L L-1 in a nutrient solution on M. hupehensis seedlings. Plant biomass, NO3- and NH4 + concentration, chlorophyll content, respiratory rate, and cellular structure were investigated. M. hupehensis seedlings at the NO3- / NH4 + ratio of50 / 50 had the highest level of fresh weight, dry weight, shoot length, and chlorophyll (a, b, and a + b) content, but the lowest respiration rate in the leaves and roots. In addition, thickness and numbers of palisade and the spongy tissue cells of the leaves were greater with this treatment than with other treatments. At the NO3- / NH4 + ratio of 100/0, the leaves and roots had higher NO3-concentration and lower NH4 + concentration. However, the opposite trend occurred at the NO3- / NH4 + ratio of 0/100. Chlorophyll (a, b, and a + b) content was lowest at the NO3- / NH4 + ratio of 100/0 than at the other ratios. At the NO3- / NH4 + ratio of 0/100, oxygen (O2) consumption increased in the leaves and roots, and irregular epidermis and cortex cells were observed in the root apical meristematic and mature region. Our results indicated that the NO3- / NH4 + ratio at 50/50 was suitable for growth of M. hupehensis seedling to achieve the highest biomass production and efficiency.