Te Aka Mātuatua - School of Science, University of Waikato, Hamilton, 3216, New Zealand.
School of Biological Science, University of Western Australia, Perth, WA, 6009, Australia.
New Phytol. 2021 Nov;232(4):1703-1717. doi: 10.1111/nph.17632. Epub 2021 Aug 24.
Current models of floral nectar production do not include a contribution from photosynthesis by green nectary tissue, even though many species have green nectaries. Mānuka (Leptospermum scoparium) floral nectaries are green, and in addition to sugars, their nectar contains dihydroxyacetone (DHA), the precursor of the antimicrobial agent in the honey. We investigated causes of variation in mānuka floral nectar production, particularly the effect of light incident on the nectary. Flower gas exchange, chlorophyll fluorescence, and the effects on nectar of age, temperature, light, sucrose, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), pyridoxal phosphate, and CO , were measured for attached and excised flowers. Flower age affected all nectar traits, whilst temperature affected total nectar sugar only. Increased light reduced floral CO efflux, increased nectar sugar production, and affected the ratio of DHA to other nectar sugars. DCMU, an inhibitor of photosystem II, reduced nectar sugar production. Pyridoxal phosphate, an inhibitor of the chloroplast envelope triose phosphate transporter, reduced nectar DHA content. Incubation of excised flowers with CO in the light resulted in enrichment of nectar sugars, including DHA. Photosynthesis within green nectaries contributes to nectar sugars and influences nectar composition. Mānuka nectar DHA arises from pools of triose phosphate that are modulated by nectary photosynthesis.
目前的花卉花蜜生产模型不包括绿色蜜腺组织光合作用的贡献，尽管许多物种都有绿色蜜腺。曼努卡（Leptospermum scoparium）的花蜜腺是绿色的，除了糖以外，它们的花蜜还含有二羟丙酮（DHA），这是蜂蜜中抗菌剂的前体。我们研究了曼努卡花卉花蜜生产的变化原因，特别是光照对蜜腺的影响。我们测量了附着和切除的花朵的花气体交换、叶绿素荧光以及花的年龄、温度、光照、蔗糖、3-(3,4-二氯苯基）-1,1-二甲基脲（DCMU）、吡哆醛磷酸盐和 CO 对花蜜的影响。花的年龄影响所有花蜜特征，而温度仅影响总花蜜糖。增加光照会降低花的 CO 排放，增加花蜜糖的产生，并影响 DHA 与其他花蜜糖的比例。DCMU，一种光合作用 II 的抑制剂，会减少花蜜糖的产生。吡哆醛磷酸盐，一种叶绿体包膜三磷酸甘油醛转运蛋白的抑制剂，会减少花蜜中的 DHA 含量。在光照下用 CO 孵育切除的花朵会导致花蜜糖的富集，包括 DHA。绿色蜜腺中的光合作用有助于花蜜糖的产生，并影响花蜜的成分。曼努卡花蜜中的 DHA 来自三磷酸甘油醛池，这些池受蜜腺光合作用的调节。
