Abstract

Deficiency and toxicity of micronutrient boron (B) play a critical role in plant productivity. In this study, the evaluation of B supplementation on biomass and essential oil (EO) yield of rose-scented geranium (Pelargonium graveolens L.) and its distribution at different application rates (2.5, 5.0, and 7.5 kg ha⁻¹) was performed in a field trial during the growing season of two consecutive years 2017–18 and 2018–19. Boron uptake, plant biomass, and EO yield along with EO constituent in leaves were determined at different time scales. Application of B significantly improved the biomass yield of P. graveolens and at B-II treatment (5.0 kg ha⁻¹ dose) highest biomass and EO yield was recorded, however, B-III treatment (7.5 kg ha⁻¹) demonstrated toxicity symptoms like the decline in protein and chlorophyll content and an increase in proline and stress enzymes (SOD, CAT) in plant leaves. The effects of B on EO constituents varied with the different developmental stages of P. graveolens. Furthermore, the application of B at 5.0 kg ha⁻¹ acts as a stimulant in upgrading the quality and quantity of EO with improved main aroma constituent’s P. graveolens than the control without modulating odor quality i.e., citronellol:geraniol (C:G) ratio. Hence, the study revealed a balanced level of B as a crucial parameter for the enhanced productivity with the improved economic return of P. graveolens.

摘要

微量元素硼 (B) 的缺乏和毒性对植物生产力起着至关重要的作用。在本研究中，对 B 补充剂对玫瑰香天竺葵 ( Pelargonium Graveolens L.) 的生物量和精油 (EO) 产量及其在不同施用率（2.5、5.0 和 7.5 kg ha ^-1）下的分布进行了评估在连续两年 2017-18 和 2018-19 生长季节的田间试验中。硼吸收、植物生物量和 EO 产量以及叶子中的 EO 成分在不同的时间尺度上确定。B 的应用显着提高了P.graveolens的生物量产量，并且在 B-II 处理（5.0 kg ha ^-1剂量）记录了最高的生物量和 EO 产量，然而，B-III 处理（7.5 kg ha^-1 ) 表现出毒性症状，例如植物叶片中蛋白质和叶绿素含量的下降以及脯氨酸和胁迫酶（SOD、CAT）的增加。B对EO成分的影响因P.graveolens不同发育阶段而异。此外，以 5.0 kg ha ^-1施用 B作为刺激剂提高了 EO 的质量和数量，与对照相比，主要香气成分的P.graveolens有所改善，而不会调节气味质量，即香茅醇：香叶醇 (C:G) 比率. 因此，该研究揭示了平衡水平的 B 作为提高生产力的关键参数，同时提高了P.graveolens 的经济回报。