Noni (Morindacitrifolia L.), a tropical, medicinal plant of the family Rubiaceae utilized since 2000 y ago by the Polynesians, is currently facing a major challenge in production vis-a-vis climate change. The worldwide average temperatures continue to fluctuate, resulting in extremely cold winters and hot summers that reduce plant productivity. Photosynthetic apparatus is an exceptionally sensitive component to estimate the degree of damage at contrasting temperatures. The present study was aimed to evaluate the temperature stress response of Noni plant using the chlorophyll a fluorescence OJIP transients (OJIP transients). Results showed the declined photosynthetic pigment pool and reduced functional and structural integrity of the photosynthetic apparatus under very low- and high-temperature treatments. Drastically lower yield parameters such as φ(Po) and φ(Eo), efficiency ψ(Eo) and performance indices - PIabs and PItotal, and accumulation of inactive reaction centers were observed. Consecutively, a lower level of calculated electron transport from PSII to PSI was observed. In contrast, the enhanced δRo indicates that PSI is more thermo-tolerant as compared to PSII. Additionally, very low and high temperatures cause an increase in antenna size (ABS/RC) and the decrease in the amplitude of I to P phase of fluorescence transient. Overall, the photosynthetic apparatus of leaf tissue was more sensitive to low and high temperatures than the developing fruit. The findings of the present study demonstrated the potential role of thylakoid components of the photosynthetic apparatus, which might be crucial in regulating the temperature stress response in the Noni plant, and thereby crop improvement.

中文翻译：

---

Noni (Morinda citrifolia L.) 植物对温度胁迫的驯化潜力是通过光合电子传递速率介导的

诺丽 (Morindacitrifolia L.) 是一种茜草科热带药用植物，自 2000 年前就被波利尼西亚人利用，目前正面临气候变化带来的生产方面的重大挑战。全球平均气温持续波动，导致极冷的冬季和炎热的夏季降低了植物的生产力。光合作用装置是一个非常敏感的组件，用于估计不同温度下的损坏程度。本研究旨在利用叶绿素 a 荧光 OJIP 瞬变（OJIP 瞬变）评估诺丽植物的温度胁迫响应。结果表明，在极低温和高温处理下，光合色素库下降，光合装置的功能和结构完整性降低。观察到极低的产率参数，例如 φ(Po) 和 φ(Eo)、效率 ψ(Eo) 和性能指数 - PIabs 和 PItotal，以及非活性反应中心的积累。连续地，观察到从 PSII 到 PSI 的计算电子传输水平较低。相反，增强的 δRo 表明与 PSII 相比，PSI 更耐热。此外，非常低和非常高的温度会导致天线尺寸 (ABS/RC) 的增加和荧光瞬态的 I 到 P 相位幅度的减小。总体而言，叶片组织的光合器官比发育中的果实对低温和高温更敏感。本研究的结果证明了光合装置的类囊体成分的潜在作用，