Plant Responses to Greenhouse Environments - Agrobotany

Introduction

Greenhouses create a managed microclimate by altering light, temperature, humidity, and atmospheric composition (notably CO₂). These controlled conditions affect plant physiology, growth form, biochemical status and development timing. Understanding these responses helps growers optimize yield, crop quality and resource use.

Major greenhouse environmental factors

• Light: Intensity, spectral quality and photoperiod change inside glazed or shaded structures and strongly influence photosynthesis and morphology.
• Temperature: Air and substrate temperatures are typically warmer and more stable; day–night ranges may be compressed.
• Carbon dioxide (CO₂): CO₂ can be naturally higher or intentionally supplemented to boost photosynthesis.
• Humidity and VPD (vapour pressure deficit): Humidity tends to be higher while VPD can be lower or variable; both affect stomatal behavior and disease risk.
• Water and nutrients: Irrigation and feeding are more uniform, changing root dynamics and nutrient uptake patterns.

Physiological responses

Photosynthesis and growth. Elevated CO₂ in greenhouses commonly raises net photosynthesis in C₃ plants and can increase biomass and growth rates when other resources (light, nutrients, water) are adequate. :contentReference[oaicite:0]{index=0}

Stomatal behaviour and water use efficiency (WUE). Higher CO₂ typically reduces stomatal aperture and can lower stomatal density over time, which reduces transpiration and often improves intrinsic water-use efficiency; however, reduced transpiration may also affect leaf cooling and mass-flow of nutrients. :contentReference[oaicite:1]{index=1}

Respiration and thermal effects. Warmer greenhouse temperatures increase respiration rates; if respiration gains exceed photosynthetic gains, net biomass accumulation may decline. Heat stress can cause enzyme dysfunction, membrane damage and oxidative stress responses. Managing temperature is therefore crucial. :contentReference[oaicite:2]{index=2}

Phenology. Plants often develop faster under favourable greenhouse conditions (leaf expansion, flowering), which can be advantageous for shortening production cycles but may alter quality traits and harvest timing.

Morphological and allocation responses

Plants may alter leaf thickness, leaf area, root:shoot ratios and overall biomass partitioning in response to greenhouse microclimate. For example, faster above-ground growth under higher CO₂ or light may be accompanied by changes in root growth and nutrient demand. These shifts are plastic and species/cultivar dependent.

Biochemical and molecular responses

Under greenhouse conditions with altered CO₂, temperature or water status, plants change carbohydrate pools (sugars, starch), secondary metabolites (phenolics, volatiles), and activate stress-protective pathways (antioxidants, heat-shock proteins). Many responses are controlled at the gene-expression level and can vary with species and developmental stage.

Trade-offs and potential problems

• Nutrient limitation: Boosted growth from CO₂ enrichment can reveal or create nitrogen or other nutrient shortages, reducing the full benefit of CO₂. :contentReference[oaicite:3]{index=3}
• Quality changes: Rapid biomass gain sometimes dilutes some quality traits (e.g., soluble solids, certain phytochemicals).
• Overheating and VPD effects: Excess heat or high VPD can stress plants and reduce yields unless ventilation, shading or cooling are used. :contentReference[oaicite:4]{index=4}
• Pest and disease pressure: High humidity and reduced airflow in greenhouses can favour fungal pathogens unless managed.

Acclimation and plasticity

Plants can acclimate physiologically and morphologically to sustained greenhouse conditions — for instance by adjusting photosynthetic capacity, enzyme complements, stomatal development and thermal tolerance. This plasticity means genotype selection and pre-conditioning are valuable tools for growers.

Practical implications for greenhouse management

• Monitor and control CO₂, temperature, light and humidity to match crop requirements (supplement CO₂ when justified and safe). :contentReference[oaicite:5]{index=5}
• Provide adequate nutrients to support increased growth under enrichment regimes to avoid nutrient dilution effects. :contentReference[oaicite:6]{index=6}
• Use ventilation, shading, evaporative cooling or other strategies to prevent overheating and excessive VPD. :contentReference[oaicite:7]{index=7}
• Choose cultivars with favorable plasticity and stress tolerance for your greenhouse system.

Summary: Greenhouse environments alter the main drivers of plant growth — light, temperature, humidity and CO₂ — producing predictable changes in photosynthesis, water relations, development and biochemical status. These changes can be harnessed to increase productivity, but require balanced management of nutrients, microclimate and cultivar choice to avoid trade-offs in quality or stress susceptibility.

Selected supporting sources

1. Review on elevated CO₂ effects on photosynthesis and growth. :contentReference[oaicite:8]{index=8}
2. Stomatal responses to elevated CO₂ and consequences for water use. :contentReference[oaicite:9]{index=9}
3. Greenhouse CO₂ supplementation practice (extension guidance). :contentReference[oaicite:10]{index=10}
4. Review of optimal greenhouse microclimate (temperature, humidity, VPD). :contentReference[oaicite:11]{index=11}
5. Comprehensive review of elevated CO₂ and plant water relations and nutrient interactions. :contentReference[oaicite:12]{index=12}