Zinc (Zn) is an essential element for human health, but at least 1/3 of the global population suffers from Zn deficiency, causing several health problems. The agronomic biofortification of lettuce with Zn is a strategy to mitigate the low intake of this nutrient by the needy population. Here we investigated the effect of agronomic biofortification of lettuce cv. Vanda with Zn on biomass production, the Zn content in leaves and antioxidant responses in two growing seasons under tropical climatic conditions. The treatments were six concentrations of Zn (0, 5, 10, 20, 30 and 40 mg Zn dm⁻³) and two growing seasons, 7 March to 6 April 2018 (S1) and 29 May to 9 July 2018 (S2). Foliar dry matter production decreased as Zn concentration increased, regardless of season, to 11.6 and 10.3 g plant⁻¹ at 0 and 40 mg Zn dm⁻³, respectively. The concentrations increased foliar Zn contents as much as 18-fold, from 41.5 to 746.3 mg Zn kg⁻¹ at 40 mg Zn dm⁻³. The concentrations from 20 mg Zn dm⁻³ increased lipid peroxidation (MDA). Foliar superoxide dismutase (SOD) activity increased at the highest concentrations (30 and 40 mg Zn dm⁻³) in both seasons. Foliar catalase (CAT) activity in S2 decreased with Zn concentrations of 20 mg dm⁻³ and higher. Foliar ascorbate peroxidase (APX) activity did not differ between Zn concentrations in either season. The milder temperatures of S2 were more favorable for biofortifying plants. Our results suggest that limiting Zn concentrations for agronomic biofortification in each growing season is important due to the sensitivity of the plant to Zn, allowing for adequate productivity and quality.

锌 (Zn) 是人类健康必不可少的元素，但全球至少有 1/3 的人口患有锌缺乏症，从而导致多种健康问题。用锌对莴苣进行农艺生物强化是一种策略，可以缓解有需要的人群对这种营养素的低摄入量。在这里，我们研究了生菜 cv 农艺生物强化的影响。Vanda 与 Zn 对热带气候条件下两个生长季节的生物量生产、叶片中的 Zn 含量和抗氧化反应。处理是六种锌浓度（0、5、10、20、30 和 40 mg Zn dm ^-3）和两个生长季节，2018 年 3 月 7 日至 4 月 6 日（S1）和 2018 年 5 月 29 日至 7 月 9 日（S2）。叶面干物质产量随着锌浓度的增加而下降，无论季节如何，植物^{-1为 11.6 和 10.3 g}分别在 0 和 40 mg Zn dm ^-3下。在 40 mg Zn dm ^-3浓度下，叶面 Zn 含量增加了 18 倍，从 41.5 到 746.3 mg Zn kg ^-1。20 mg Zn dm ^-3的浓度增加了脂质过氧化（MDA）。叶面超氧化物歧化酶 (SOD) 活性在两个季节都在最高浓度（30 和 40 mg Zn dm ^{-3 ）下增加。}S2 中的叶面过氧化氢酶 (CAT) 活性随着 20 mg dm ^{-3的 Zn 浓度而降低}和更高。叶面抗坏血酸过氧化物酶 (APX) 活性在任一季节的锌浓度之间没有差异。S2 较温和的温度更有利于植物的生物强化。我们的研究结果表明，由于植物对锌的敏感性，限制每个生长季节的农艺生物强化的锌浓度非常重要，可以保证足够的生产力和质量。