Developmental sequences for simulating crop phenology for water-limiting conditions

The timing, duration, and pace of developmental events, or phenology, are among the many responses of plants to limited soil water. Understanding and predicting plant responses to availability of soil water are important in improving the efficacy of management practices. However, the first steps towards gaining this understanding, summarising the complete developmental sequence of the shoot apex and correlating the timing of these events, have rarely been reported. Also, the effect of water-limiting conditions on crop phenology and shoot apex development is variable. The objective of this paper is to present the developmental sequence of the wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and corn (Zea mays L.) shoot apices and correlate events in these sequences with growth stages for both well-watered and water-limiting conditions. We note that phenological responses to water availability occur at 3 different scales: among crops, among cultivars of a crop, and among growth stages within a cultivar or crop. Clearly, genotype × environment interaction affects the accuracy of predicting phenology. However, the fact that plants develop in an orderly, predictable pattern allows a general foundation for synthesising the complete sequence of developmental events of the shoot apex and correlate these with growth stages when water is not limiting. These patterns and relationships are the foundation to build upon in quantifying our understanding of crop phenology under water-limiting environments.