Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan.
Core Research for Evolutional Science and Technology (CREST), Kawaguchi, Saitama, 332-0012, Japan.
Plant Cell Environ. 2015 Dec;38(12):2629-40. doi: 10.1111/pce.12573. Epub 2015 Jul 28.
To reveal whether hypocotyl sink activities are regulated by the aboveground parts, and whether physiology and morphology of source leaves are affected by the hypocotyl sink activities, we conducted grafting experiments using two Raphanus sativus varieties with different hypocotyl sink activities. Comet (C) and Leafy (L) varieties with high and low hypocotyl sink activities were reciprocally grafted and resultant plants were called by their scion and stock such as CC, LC, CL and LL. Growth, leaf mass per area (LMA), total non-structural carbohydrates (TNCs) and photosynthetic characteristics were compared among them. Comet hypocotyls in CC and LC grew well regardless of the scions, whereas Leafy hypocotyls in CL and LL did not. Relative growth rate was highest in LL and lowest in CC. Photosynthetic capacity was correlated with Rubisco (ribulose 1·5-bisphosphate carboxylase/oxygenase) content but unaffected by TNC. High C/N ratio and accumulation of TNC led to high LMA and structural LMA. These results showed that the hypocotyl sink activity was autonomously regulated by hypocotyl and that the down-regulation of photosynthesis was not induced by TNC. We conclude that the change in the sink activity alters whole-plant growth through the changes in both biomass allocation and leaf morphological characteristics in R. sativus.
为了揭示下胚轴库活动是否受地上部分的调节，以及源叶的生理学和形态学是否受下胚轴库活动的影响，我们使用两种具有不同下胚轴库活性的萝卜品种进行了嫁接实验。彗星（C）和多叶（L）品种具有高和低的下胚轴库活性，它们相互嫁接，所得植株分别称为接穗和砧木，如 CC、LC、CL 和 LL。比较了它们之间的生长、叶面积比（LMA）、总非结构性碳水化合物（TNC）和光合作用特性。无论接穗如何，CC 和 LC 中的彗星下胚轴生长良好，而 CL 和 LL 中的叶片下胚轴则不然。相对生长率在 LL 中最高，在 CC 中最低。光合能力与 RuBisCO（核酮糖-1,5-二磷酸羧化酶/加氧酶）含量相关，但不受 TNC 影响。高 C/N 比和 TNC 的积累导致 LMA 和结构 LMA 升高。这些结果表明，下胚轴库活性是由下胚轴自主调节的，光合作用的下调不是由 TNC 诱导的。我们得出结论，在萝卜中，通过改变生物量分配和叶片形态特征，库活性的变化会改变整个植株的生长。
