Photochemical efficiency in pineapple plants under saline water irrigation

Abstract Studies determining physiological characteristics of field-grown pineapples irrigated with low-quality water are lacking. This work evaluated the photochemical efficiency of ‘Pérola’ pineapple irrigated with saline water in the semiarid region of Bahia, Brazil. The experiment was carried out in randomized blocks with five treatments consisting of the following irrigation depths: 100% of ETc using water with electrical conductivity (ECw) of 0.75 dS m-1; and 50, 75, 100 and 125% of ETc using water with ECw of 3.6 dS m-1. Chlorophyll a fluorescence measurements were made over the course of 13 months using a pulse-modulated fluorometer, in all treatments. Quantum efficiency (Fv/Fm) fluctuated throughout the cycle of the pineapple with values below the ideal, especially at the end of the crop cycle. Quantum yield of photosystem II (Yield), photochemical quenching (qP), non-photochemical quenching (NPQ) and chlorophyll fluorescence decrease ratio (RFd) were not influenced by irrigation depths. Therefore, energy used for photosynthetic processes in pineapple plants is not affected by irrigation using saline water with electrical conductivity of 3.6 dS m-1.

摘要 目前针对采用劣质水源灌溉的大田栽培菠萝开展生理特性研究的相关报道仍较为匮乏。本研究以巴西巴伊亚州半干旱地区采用咸水灌溉的‘珍珠’（Pérola）菠萝为研究对象，对其光化学效率进行评估。试验采用随机区组设计，设置5个灌溉梯度处理：以水的电导率（electrical conductivity of water, ECw）为0.75 dS·m⁻¹的水源灌溉，灌溉量为作物蒸发蒸腾量（crop evapotranspiration, ETc）的100%；以及以ECw为3.6 dS·m⁻¹的咸水灌溉，灌溉量分别为ETc的50%、75%、100%和125%。所有处理组均采用脉冲调制式荧光仪（pulse-modulated fluorometer）开展为期13个月的叶绿素a荧光测定。量子效率（Fv/Fm）在菠萝整个生育周期内存在波动，其数值低于理想阈值，尤其在作物生育周期末期表现更为显著。光系统II量子产额（quantum yield of photosystem II, Yield）、光化学淬灭系数（photochemical quenching, qP）、非光化学淬灭系数（non-photochemical quenching, NPQ）以及叶绿素荧光衰减比率（chlorophyll fluorescence decrease ratio, RFd）均未受到灌溉梯度的显著影响。综上，采用电导率为3.6 dS·m⁻¹的咸水灌溉，不会对菠萝植株光合过程的能量利用产生影响。