Narvarte Bienson Ceasar V, Roleda Michael Y
Algal Ecophysiology Laboratory (AlgaE Lab), The Marine Science Institute, College of Science, University of the Philippines, Diliman 1101, Quezon City, Philippines; Bolinao Marine Laboratory, UPMSI, Guiguiwanen, Luciente 1, Bolinao, Pangasinan, Philippines.
Algal Ecophysiology Laboratory (AlgaE Lab), The Marine Science Institute, College of Science, University of the Philippines, Diliman 1101, Quezon City, Philippines; Bolinao Marine Laboratory, UPMSI, Guiguiwanen, Luciente 1, Bolinao, Pangasinan, Philippines.
Plant Physiol Biochem. 2025 Jun;223:109846. doi: 10.1016/j.plaphy.2025.109846. Epub 2025 Mar 26.
The availability and proportion of ammonium (NH) and nitrate (NO) in the marine environment fluctuate due to various processes such as upwelling, regeneration, pollution, nitrogen fixation, among others, significantly impacting the physiology and biochemistry of seaweeds. Hence, this study aims to examine the effects of varying NH: NO ratio on the growth, nutrient uptake, and biochemical composition (carbohydrate, protein, polyphenol, and pigment content) of commercially important eucheumatoid-crops Kappaphycus alvarezii, Kappaphycus striatus, and Eucheuma denticulatum. Apical portions of the seaweed samples were cultured under controlled laboratory conditions for 15 d in seawater media with a constant total nitrogen concentration of 40 μM but differing NH:NO ratios (40:0, 30:10, 20:20, 10:30, 0:40). Growth differed among species, with K. alvarezii showing highest growth rate when cultured in media containing NH as the sole source of inorganic nitrogen and K. striatus displaying lowest growth in media with NO as the only inorganic nitrogen source. E. denticulatum had the highest range of growth rate, but showed no sensitivity to alterations in nitrogen species proportion. Generally, the NH uptake rates of eucheumatoids decreased as the proportion of NH in the treatment decreased, while their NO uptake rates increased as the concentration of NO became more dominant. Notably, eucheumatoids absorbed more total inorganic nitrogen when both nitrogen species were available than when only one was present. Nitrate reductase activities (NRA) were similar regardless of the NH:NO ratio except for E. denticulatum which had the highest NRA when only NO was present in the media. Despite differences in growth, nutrient uptake and NRA, the biochemical composition of the three eucheumatoid species remained consistent across nitrogen ratios, indicating that inorganic nitrogen proportions had minimal impacts on resource allocation to biochemical constituents. Together, our results suggest that while physiological processes such as nutrient acquisition and enzymatic activity were sensitive to inorganic nitrogen proportions, these changes did not translate into significant alterations in the allocation of resources to biochemical constituents under the experimental conditions. Understanding these dynamics is crucial for the sustainable cultivation of these commercially important seaweeds under varying environmental conditions.
由于上升流、再生、污染、固氮等各种过程，海洋环境中铵（NH）和硝酸盐（NO）的可利用性和比例会发生波动，这对海藻的生理和生物化学有显著影响。因此，本研究旨在探讨不同NH:NO比例对具有商业重要性的麒麟菜属作物——卡帕藻、条纹卡帕藻和细齿麒麟菜的生长、养分吸收及生化组成（碳水化合物、蛋白质、多酚和色素含量）的影响。将海藻样本的顶端部分在实验室控制条件下，于总氮浓度恒定为40 μM但NH:NO比例不同（40:0、30:10、20:20、10:30、0:40）的海水培养基中培养15天。不同物种的生长情况有所不同，当卡帕藻在以NH作为唯一无机氮源的培养基中培养时，其生长速率最高；而条纹卡帕藻在以NO作为唯一无机氮源的培养基中生长最慢。细齿麒麟菜的生长速率范围最高，但对氮形态比例的变化不敏感。一般来说，麒麟菜属作物的NH吸收速率随着处理中NH比例的降低而下降，而它们的NO吸收速率随着NO浓度占主导地位而增加。值得注意的是，当两种氮形态都存在时，麒麟菜属作物吸收的总无机氮比仅存在一种氮形态时更多。除了细齿麒麟菜在培养基中仅存在NO时具有最高的硝酸还原酶活性（NRA）外，无论NH:NO比例如何，硝酸还原酶活性都相似。尽管在生长、养分吸收和NRA方面存在差异，但三种麒麟菜属物种的生化组成在不同氮比例下保持一致，这表明无机氮比例对生化成分资源分配的影响最小。总之，我们的结果表明，虽然养分获取和酶活性等生理过程对无机氮比例敏感，但在实验条件下，这些变化并未转化为生化成分资源分配的显著改变。了解这些动态对于在不同环境条件下可持续养殖这些具有商业重要性的海藻至关重要。
