Growth, Physiological, Biochemical, and Ionic Responses of Morus alba L. Seedlings to Various Salinity Levels

Nan Lu,Yuzhou Ke,Suhan Dou,Yuhan Sun,Rongxuan Hou,Binbin Cui,Hongjing Duan,Yadong Zhang,Zijing Luo,Yun Li,Li Dai

doi:10.3390/f8120488

Abstract

Mulberry (Morus alba L.), a moderately salt-tolerant tree species, is considered to be economically important. In this study, 1-year-old mulberry seedlings cultivated in soil under greenhouse conditions were treated with five concentrations of sodium chloride (NaCl; 0%, 0.1%, 0.2%, 0.3%, and 0.5%) for 3 and 21 days. Plant growth parameters were not affected by 0.1% NaCl, but significant reductions were observed after treatment with 0.2%, 0.3%, and 0.5% NaCl. The malondialdehyde content and cell membrane stability of mulberry seedlings exposed to 0.1% NaCl did not change, indicating that mulberry is not significantly affected by low-salinity conditions. The Na contents of various organs did not increase significantly in response to 0.1% NaCl, but the K:Na, Mg:Na, and Ca:Na ratios of various organs were affected by NaCl. Marked changes in the levels of major compatible solutes (proline, soluble sugars, and soluble proteins) occurred in both the leaves and roots of NaCl-treated seedlings relative to control seedlings. Under severe saline conditions (0.5% NaCl), the ability of mulberry to synthesize enzymatic antioxidants may be impaired.

Highlights

Plants are exposed to multiple abiotic stresses in their natural surroundings
We investigated the effects of different NaCl concentrations on the growth, gas exchange, osmotic adjustment, antioxidant enzyme content, and ionic content of mulberry seedlings subjected to salt stress for 3 days and 21 days
Saline conditions had negative effects on plant growth, and reductions in growth became more pronounced with increasing levels of salt in the soil; the average leaf area and the lengths and diameters of lateral roots were higher under low-salinity conditions (0.1% NaCl) than in the untreated control plants (Table 1)

Summary

Introduction

Plants are exposed to multiple abiotic stresses in their natural surroundings. Abiotic stress conditions such as high or low temperature, drought, and salinity are common unfavorable conditions that have negative effects on tree growth and production. Among these stresses, soil salinity imposes a major constraint on forestry production because it restricts growth and limits the use of uncultivated land [1]. High-salt environments can interfere with the ion homeostasis of plant cells, disrupt the Forests 2017, 8, 488; doi:10.3390/f8120488 www.mdpi.com/journal/forests. Salt stress induces the formation of reactive oxygen species (ROS), which participate in a wide range of reactions with negative effects such as lipid peroxidation, pigment oxidation, membrane disruption, protein denaturation, and DNA mutation [4]

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