Nitrogen fertilization to attenuate the damages caused by salinity on yellow passion fruit seedlings

ABSTRACT The study aimed to evaluate the mitigating effect of nitrogen (N) on the damages caused by irrigation water salinity, in the production of yellow passion fruit seedlings. A randomized block design in split plots was used, with five levels of irrigation water salinity (plot) (0.3, 1.0, 1.7, 2.4 and 3.1 dS m-1) and five doses of N fertilization (sub-plot) (180, 240, 300, 360 and 420 mg of N dm-3), with five replicates, totaling 125 experimental units, with one plant per plot. The seedlings were produced in 3.780 mL tubes, used as drainage lysimeter, which received a daily irrigation depth based on water balance. Growth and contents of chlorophyll and carotenoids were evaluated at 85 days after sowing. The increase in irrigation water salinity reduced stem diameter, plant height, number of leaves, chlorophyll a, chlorophyll b and total chlorophyll; increasing N doses also led to linear decline in stem diameter and plant height. Application of increasing doses of N did not attenuate the effect of salinity on growth and pigment contents.

摘要
本研究旨在探究氮肥（nitrogen, N）对灌溉水盐度胁迫所致损伤的缓解效应，以黄百香果种苗繁育为试验对象。试验采用裂区随机区组设计，设置5个灌溉水盐度梯度（主区）：0.3、1.0、1.7、2.4、3.1 dS·m⁻¹，以及5个氮肥施用量梯度（副区）：180、240、300、360、420 mg N·dm⁻³，共设置5次重复，总计125个试验单元，每个单元种植1株种苗。试验种苗在容积为3.780 L的试管（用作排水型蒸渗仪）中培育，灌溉水深依据水量平衡逐日调控。于播种后85天，测定种苗的生长指标及叶绿素、类胡萝卜素含量。结果显示，灌溉水盐度升高会降低种苗茎粗、株高、叶片数、叶绿素a、叶绿素b及总叶绿素含量；而氮肥施用量增加同样会导致茎粗与株高呈线性下降。提升氮肥施用量并未缓解盐度对种苗生长及色素含量的胁迫效应。