The calcium ion (Ca²⁺) is a universal signal in all eukaryotic cells. A fundamental question is how Ca²⁺, a simple cation, encodes complex information with high specificity. Extensive research has established a two-step process (encoding and decoding) that governs the specificity of Ca²⁺ signals. While the encoding mechanism entails a complex array of channels and transporters, the decoding process features a number of Ca²⁺ sensors and effectors that convert Ca²⁺ signals into cellular effects. Along this general paradigm, some signalling components may be highly conserved, but others are divergent among different organisms. In plant cells, Ca²⁺ participates in numerous signalling processes, and here we focus on the latest discoveries on Ca²⁺-encoding mechanisms in development and biotic interactions. In particular, we use examples such as polarized cell growth of pollen tube and root hair in which tip-focused Ca²⁺ oscillations specify the signalling events for rapid cell elongation. In plant–microbe interactions, Ca²⁺ spiking and oscillations hold the key to signalling specificity: while pathogens elicit cytoplasmic spiking, symbiotic microorganisms trigger nuclear Ca²⁺ oscillations. Herbivore attacks or mechanical wounding can trigger Ca²⁺ waves traveling a long distance to transmit and convert the local signal to a systemic defence program in the whole plant. What channels and transporters work together to carve out the spatial and temporal patterns of the Ca²⁺ fluctuations? This question has remained enigmatic for decades until recent studies uncovered Ca²⁺ channels that orchestrate specific Ca²⁺ signatures in each of these processes. Future work will further expand the toolkit for Ca²⁺-encoding mechanisms and place Ca²⁺ signalling steps into larger signalling networks.

钙离子（Ca ²⁺）是所有真核细胞中的普遍信号。一个基本问题是简单的阳离子Ca ²⁺如何以高特异性编码复杂信息。广泛的研究已经建立了控制Ca ²⁺信号特异性的两步过程（编码和解码）。虽然编码机制需要复杂的通道和传输器阵列，但解码过程的特征是将Ca ²⁺信号转换为细胞效应的大量Ca ²⁺传感器和效应器。沿着这种一般范式，某些信号成分可能是高度保守的，但其他信号成分在不同生物之间是不同的。在植物细胞中，Ca ²⁺参与众多的信号传导过程，在这里，我们着重于有关Ca ²⁺编码机制在发育和生物相互作用中的最新发现。特别是，我们使用了一些例子，例如花粉管和根毛的极化细胞生长，其中尖端的Ca ²⁺振荡指定了细胞快速伸长的信号传导事件。在植物与微生物的相互作用中，Ca ^2+的尖峰和振荡是信号特异性的关键：病原体引起细胞质的尖峰，而共生微生物则触发核Ca ^2+的振荡。草食动物的攻击或机械性伤害会触发Ca ²⁺长距离传播的电波将本地信号传输并将其转换为整个工厂的系统防御程序。哪些渠道和运输商共同努力，找出Ca ²⁺涨落的时空格局？几十年来一直困扰着这个问题，直到最近的研究发现在这些过程的每一个过程中都可以编排特定的Ca ²⁺特征的Ca ²⁺通道。未来的工作将进一步扩展用于Ca ²⁺编码机制的工具包，并将Ca ²⁺信号传递步骤放入更大的信号网络中。