French Associates Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 84990, Midreshet Ben Gurion, Israel.
Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, 710-0046, Japan.
Planta. 2020 Oct 8;252(5):77. doi: 10.1007/s00425-020-03491-2.
The dead husk is a vital component of the dispersal unit whose biochemical properties can be modified following exposure to drought. This might affect seed performance and fate, soil properties and consequently plant biodiversity. We investigated the effects of extreme drought on the dispersal unit (DU) properties of winter wild oat (Avena sterilis L.) in the Mediterranean ecosystems focusing on a commonly ignored component of the DU, namely the dead floral bracts (husk). DUs were collected from a climate change experimental research station in the Judean Hills, Israel, simulating extreme drought and from two additional sites differing in the rainfall amounts. Our results showed that drought conditions significantly affected A. sterilis reproductive traits displaying reduced DUs and caryopses weights. The husk contributes profoundly to seed performance showing that germination from the intact DUs or the intact florets 1 was higher, faster and more homogenous compared to naked caryopses; no effect of drought on germination properties was observed. The husk stored hundreds of proteins that retain enzymatic activity and multiple metabolites including phytohormones. Changes in rainfall amounts affected the composition and levels of proteins and other metabolites accumulated in the husk, with a notable effect on abscisic acid (ABA). The husk of both control and drought plants released upon hydration substances that selectively inhibited other species seed germination as well as substances that promoted microbial growth. Our data showed that the dead husk represents a functional component of the DU that have been evolved to nurture the embryo and to ensure its success in its unique habitat. Furthermore, drought conditions can modify husk biochemical properties, which in turn might affect seed performance and fate, soil microbiota and soil fertility and consequently plant species diversity.
死亡的颖壳是传播单位的一个重要组成部分，其生化特性可以在暴露于干旱后发生改变。这可能会影响种子的性能和命运、土壤特性，从而影响植物生物多样性。我们研究了极端干旱对冬季野燕麦（Avena sterilis L.）传播单位（DU）特性的影响，重点研究了 DU 中一个通常被忽视的组成部分，即死亡的花被片（颖壳）。DU 是从以色列朱迪亚山的一个气候变化实验研究站收集的，模拟了极端干旱条件，以及另外两个降雨量不同的地点。我们的研究结果表明，干旱条件显著影响了 A. sterilis 的生殖特征，表现为 DU 和颖果的重量减少。颖壳对种子的性能有重要影响，结果表明，完整 DU 或完整小花 1 的种子萌发更快、更均匀，活力更高；而干旱对萌发特性没有影响。颖壳中储存了数百种具有酶活性的蛋白质和多种代谢物，包括植物激素。降雨量的变化影响了颖壳中积累的蛋白质和其他代谢物的组成和水平，对脱落酸（ABA）有显著影响。在水合作用下，无论是对照植株还是干旱植株的颖壳都会释放出物质，这些物质会选择性地抑制其他物种的种子萌发，同时也会促进微生物的生长。我们的数据表明，死亡的颖壳代表了 DU 的一个功能性组成部分，它是为了培育胚胎并确保其在独特的生境中成功而进化而来的。此外，干旱条件可以改变颖壳的生化特性，这反过来又可能影响种子的性能和命运、土壤微生物群落和土壤肥力，从而影响植物物种多样性。
