A glasshouse, also known as a greenhouse, is a structure designed to provide a controlled environment for plant growth. Three important environmental factors that can be controlled in a glasshouse to improve crop yield are temperature, humidity, and light. Here is a brief explanation of how these factors can be controlled:

1. Temperature: Temperature is a critical environmental factor that affects plant growth and development. Glasshouses have various methods of controlling temperature, such as ventilation systems, shading, and heating systems. Ventilation systems can help to regulate the temperature by allowing hot air to escape and cool air to enter. Shading can also be used to prevent excessive sunlight from entering the glasshouse and causing the temperature to rise. Heating systems, on the other hand, can be used to maintain the temperature during cold weather. By controlling the temperature, plant growth can be optimized, leading to better crop yield.

2. Humidity: Humidity refers to the amount of moisture in the air. Glasshouses have the ability to control humidity by using systems such as evaporative cooling and misting. Evaporative cooling works by introducing water into the air and allowing it to evaporate, which helps to cool the air and increase humidity levels. Misting, on the other hand, involves spraying a fine mist of water onto the plants, which helps to increase humidity levels and reduce stress on the plants. By controlling the humidity, plants can grow in a more optimal environment, which can improve their yield.

3. Light: Light is an important environmental factor that is essential for plant growth. Glasshouses can control light by using shading and artificial lighting. Shading can be used to prevent excessive sunlight from entering the glasshouse and causing damage to the plants. Artificial lighting can also be used to supplement natural light, especially during the winter months when there is less sunlight. By providing the right amount and quality of light, plant growth can be optimized, which can lead to better crop yield.