滨海盐碱地秋葵果实性状时序变化特征

Temporal variation of okra fruit traits in coastal saline-alkali soil

  • 摘要: 由治理盐碱地适应作物向耐盐碱植物适应盐碱地转变是盐碱地综合利用的新方向。在中重度盐碱地种植耐盐性强的高值作物秋葵, 不仅能降盐培肥, 还可提升盐碱地经济效益。本研究河北省沧州市南大港中度盐碱地(全盐含量约4‰), 调查了秋葵果实发育过程中产量、色泽和营养组分及其之间关系的变化规律, 通过主成分分析和隶属函数法计算产量、色泽和营养的得分值, 为确定秋葵的最佳采摘时间提供指导。研究结果表明, 随着秋葵果实的生长发育, 其鲜重和干重持续增长, 在生长15 d时达到最大值(7月最大干重为12.31±0.27 g; 8月最大干重为11.97±0.24 g; 9月最大干重为7.45±0.19 g); 横径和纵径呈先快速增大后略微减小的趋势, 在花后11 d进入平台期(横径2.12~2.30 cm, 纵径14.00~17.75 cm)。叶绿素a的含量呈略微上升趋势, 叶绿素b的含量则逐渐下降, 总叶绿素含量保持稳定7月变异系数(CV)=3.56%; 8月CV=3.04%; 9月CV=10.07%。可溶性糖和类黄酮含量呈先升高后降低趋势, 在生长5~7 d时达到峰值(最高值分别为158.92±4.69 mg·g−1和33.07±2.74 mg·g−1), 总膳食纤维含量则线性增长; 矿质元素钙呈现先降低后逐渐平缓的规律, 铁和锌含量变化不显著。产量形成、色泽变化与营养代谢存在明显的权衡关系, 但最优平衡点的出现时间在采摘月份之间存在差异。7—8月秋葵适宜的采摘期为果实生长5 d, 9月秋葵的适宜采摘期为生长7 d。研究结果可为盐碱地特色农产品开发提供理论支撑, 推动“以种适地”生态农业模式的实践应用。

     

    Abstract: The utilization of saline-alkali land is undergoing a paradigm shift from traditional soil remediation-driven strategies to the adaptive cultivation of salt-tolerant plants. Okra Abelmoschus esculentus L. (Moench), a species with strong salt tolerance, offers dual benefits when cultivated in moderately to severely saline-alkali soils: it enhances soil desalination and fertility while generating economic value. However, the dynamic changes in okra fruit quality traits in saline-alkali habitats, particularly the coordinated response patterns of yield components, color development, and nutritional metabolites across different growth stages, remain poorly understood. This gap limits the development of targeted quality regulation strategies for high-value agricultural products in such marginal environments. To address this, a field study was conducted in the saline-alkali regions of Nandagang, Cangzhou (with the total salt content of about 4‰), analyzing the traits of okra fruits at different growth stages. Key traits included yield parameters (transverse and longitudinal diameters, fresh and dry weight), chlorophyll content (chlorophyll a, chlorophyll b, and total chlorophyll), and nutritional components flavonoids, soluble sugars, total dietary fiber, and mineral elements (Ca, Fe, Zn). The universality of observed patterns was further validated across different harvesting months (July–September). Principal component analysis (PCA) and membership function methods were employed to calculate composite scores for these traits, guiding the determination of the optimal harvest time for okra. The results indicated that as the okra fruits developed, the fresh weight and dry weight progressively increased, peaking at 15d post-anthesis (dry weight: 12.31±0.27 g in July, 11.97±0.24 g in August, and 7.45±0.19 g in September). Fruit size (transverse and longitudinal diameters) exhibited rapid initial growth followed by stabilization at 11 d post-anthesis (2.12–2.30 cm and 14.0–17.75 cm, respectively). Chlorophyll a content showed a slight upward trend, while chlorophyll b content gradually decreased over time. Total chlorophyll content remained stable with low variability Coefficient of Variation (CV) = 3.56% in July, CV = 3.04% in August, and CV = 10.07% in September. Soluble sugar and flavonoid contents first rose and then fell, peaking at 5-7 days post-anthesis (158.92±4.69 mg·g-1 and 33.07±2.74 mg·g-1, respectively), whereas total dietary fiber content accumulated linearly. Mineral elements exhibited distinct patterns: calcium decreased initially before stabilizing, while iron and zinc showed no significant changes. The fruit size, weight, and accumulation patterns of chlorophyll b, total chlorophyll, and mineral elements in okra fruits were consistent across the three harvesting cycles from July to September. In contrast, the developmental trends of chlorophyll a content, soluble sugar content, flavonoid content, and total dietary fiber demonstrated month-specific variations. A trade-off relationship was observed among yield, color and nutritional components, but the timing of the optimal balance point varied among the months. The results indicated that in saline-alkali environments, okra fruits exhibit delayed morphological development but enhanced accumulation of osmotic substances. Recommended plucking periods were 5 days post-anthesis for July and August, and 7 days post-anthesis for September. These findings provide theoretical support for developing saline-alkali-adapted agricultural products, advance the practical implementation of the "planting suitable crops for specific lands" ecological agriculture model, and support the sustainable exploitation of saline-alkali lands.

     

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