<b><i>Agaricus bisporus</i></b><b> mushrooms are supplied with water through both apoplastic as well as symplastic routes from distinct substrate layers</b>

<i>Agaricus bisporus </i>is grown commercially on compost topped with a peat-based casing layer. Water is translocated from compost and casing to enable formation of mushrooms. Here, water translocation from casing and different parts of the compost into mushrooms was studied and linked to their water potential and contributing factors thereof: i.e. osmotic- and matric potentials. Water in the mushrooms mainly originated from the casing and to a lesser extent from the top and middle layers of the compost. Based on these results, alternative casing regimes were tested to increase mushroom production. This resulted in a total yield increase of up to 1.4-fold when the old casing was topped with a fresh layer of casing or when the casing was replaced after harvesting the second flush. Data indicate that the difference in water potential can drive passive water translocation from the casing to the first flush, without expending cellular energy. However during the second flush, no such water potential gradient is established between casing and the mushrooms, yet mushrooms still develop. The water potential in the compost indicates that water cannot be translocated to the mushrooms at all. Therefore, other components of the water potential should drive this water flow. We have indications that this component is the turgor of the mycelium. Moreover, we found a novel route of water translocation from casing to mushrooms via the apoplast.双孢蘑菇（Agaricus bisporus）的商业化栽培通常以堆肥基质为培养基质，并覆盖以泥炭为主要成分的覆土层。水分从堆肥基质与覆土层中转运，为子实体（蘑菇）的形成提供必要条件。本研究针对覆土层及堆肥基质不同部位向子实体的水分转运过程展开探究，并将其与子实体水势及其影响因素——即渗透势与基质势——建立关联。研究结果显示，子实体中的水分主要源自覆土层，仅少量来自堆肥基质的表层与中层。基于上述发现，本研究测试了多种改良型覆土管理方案以提升子实体产量。结果表明，当在旧覆土层上方添加新鲜覆土层，或在采收第二潮菇后更换全部覆土时，子实体总产量最高可提升至原来的1.4倍。数据显示，水势差可驱动水分从覆土层向第一潮菇进行被动转运，无需消耗细胞能量。但在第二潮菇生长阶段，覆土层与子实体之间未形成此类水势梯度，子实体却仍可正常发育。堆肥基质的水势检测结果显示，水分完全无法向子实体转运，因此水势的其他组成部分应是该水分流动的驱动力。本研究有证据表明，该驱动力为菌丝膨压。此外，本研究还发现了一条从覆土层到子实体的新型水分转运路径——经由质外体（apoplast）。