GAS EXCHANGE, CHLOROPLAST PIGMENTS AND GROWTH OF PASSION FRUIT CULTIVATED WITH SALINE WATER AND POTASSIUM FERTILIZATION 1

ABSTRACT The objective of this study was to evaluate the gas exchange, chloroplast pigments and growth of ‘BRS Rubi do Cerrado’ passion fruit as a function of irrigation with saline water and potassium fertilization in the seedling formation stage. The experiment was conducted under greenhouse conditions in the municipality of Pombal-PB, Brazil. A randomized block design was used in 5 x 2 factorial scheme, corresponding to five levels of water electrical conductivity - ECw (0.3, 1.1, 1.9, 2.7 and 3.5 dS m-1) and two doses of potassium - KD (50 and 100% of the recommendation), with four replicates and two plants per plot. Water salinity from 0.3 dS m-1 reduced the stomatal opening, transpiration, CO2 assimilation and inhibited the growth of ‘BRS Rubi do Cerrado’ passion fruit plants, at 40 days after sowing. There was no CO2 restriction in the substomatal cavity of passion fruit plants grown under water salinity from 0.3 dS m-1. Potassium dose of 150 mg kg-1 of soil, corresponding to 100%, intensified the effect of salt stress on the assimilation rate and instantaneous carboxylation efficiency in 'BRS Rubi do Cerrado' passion fruit. There was interaction between water salinity levels and potassium doses for the chlorophyll a and b contents of 'BRS Rubi do Cerrado' passion fruit.

摘要 本研究旨在评估育苗阶段咸水灌溉与钾肥配施对‘BRS Rubi do Cerrado’西番莲的气体交换特性、叶绿体色素含量及生长状况的影响。试验于巴西帕拉伊巴州蓬巴尔市的温室环境中开展，采用5×2因子设计的随机区组方案，设置5个灌溉水电导率（electrical conductivity, ECw）水平：0.3、1.1、1.9、2.7和3.5 dS·m⁻¹，以及2个钾肥施用量（potassium dose, KD）水平，分别为推荐用量的50%和100%，共设置4次重复，每小区种植2株幼苗。播种后40天，当灌溉水的电导率从0.3 dS·m⁻¹开始升高时，会降低‘BRS Rubi do Cerrado’西番莲植株的气孔开度、蒸腾速率与CO₂同化速率，并抑制其生长发育；在0.3 dS·m⁻¹咸水灌溉条件下生长的该品种西番莲，其气孔下腔未出现CO₂限制现象。当钾肥施用量为150 mg·kg⁻¹土壤（对应推荐用量的100%）时，会加剧盐胁迫对‘BRS Rubi do Cerrado’西番莲同化速率与瞬时羧化效率的负面影响。‘BRS Rubi do Cerrado’西番莲的叶绿素a、b含量存在水盐水平与钾肥施用量的交互效应。