Regulation of Crop Growth

栽培作物的目的是為了滿足人類的需求，其最終目標在於生產能廣為消費者 所接受的高品質農產品，生產者從中可以獲取最高的利益。作物的產能受作物本 身、生長的土壤環境、氣候環境、栽培者的管理技術、社經因子以及各因素之交 互作用決定。土壤的物理、化學及生物特性可直接或間接影響到根系的生長發 育、水分吸收、養分吸收，進而影響到作物的產量與品質。植物根部吸收養分是 一種變動複雜的過程，養分的吸收主要取決於根表面無機養分的濃度、根本身的 吸收能力以及植物對無機養分的需求量。養分可透過質流、擴散作用及根截取被 吸收到根部。溫度與光線是環境因子中決定作物生長發育最重要且關鍵的因子， 溫度決定代謝速率，影響一般的生理作用，因此每一種作物皆有最適當的生長溫 度，不適當的溫度降低生長及代謝活性。光線不僅直接影響光合作用，導致作物 生產力不同，同時也調節作物的生長發育，改變形態及影響開花，溫度與光線交 互作用影響作物的生長。由於作物的生長發育受環境因子調控，作物會因應環境 的變化產生適應性改變，減少逆境傷害。作物的生長是透過土壤、環境、植物與 人交互作用所產生的結果，要得到最佳產能必需評估量化各項因子及其交互作用 的影響程度，因此透過調控栽培環境、改變作物的生理特性、採用改良的栽培技 術與品種，可營造適合作物生長的環境，達到高產的目標。 The main aim of crop cultivation is to provide high yield, good quality, and healthy products to meet the demand of mankind and obtain maximum return profit by the producer. Crop productivity or yield is a function of environmental, plant, management, and socioeconomical factors and their interaction. The characters of soil physical, chemical, and biological directly or indirectly affect plant root growth, absorption of water and nutrients, and, consequently, plant growth and yield. Nutrient absorption by plant roots is a dynamic and complex process. The rate of nutrient absorption by a root depends on the nutrient supply to the surface, active absorption by roots, and plant demand for nutrients. Nutrients are transported to the root by mass flow, diffusion, and root interception. Temperature and solar radiation are important and often critical environmental factors for plant growth and development. Reaction rate in plant processes is a function of temperature. Each plant species has an optimum temperature range for growth and reproduction. Heat stress can result in reduced growth and other metabolic activities. Light not only affect photosynthesis and consequently crop productivity, but also regulate plant growth and development that result in stem length, leaf size and thickness, amount of branching, relative root size, and flowering. Some of the light-regulated processes are modified by temperature. Plant growth and development ultimately depend upon environmental variables, such as temperature, light, and availability of water and mineral nutrients. Plants constantly sense the changes in their environment and exhibit a broad range of morphogenic responses. The stress-induced morphogenic response is a general acclimation strategy, whereby plant growth is redirected to diminish stress exposure. Crop growth is the product of interactions involving climate, soil, plants, and people. Quantitative evaluation of these factors and their interactions should become increasingly important in evaluating systems that optimize yield. Most of the crop production factors can be modified in favor of higher yields by modifying the environment or the physiological characteristics of the crop and by developing cultural practices and cultivars to exploit a specific agricultural environment