What environmental condition would likely decrease plant growth?

High soil salinity can significantly decrease plant growth due to its adverse effects on plant physiology. When the salt concentration in the soil is elevated, it creates a hypertonic environment around the plant roots. This means that water tends to move out of the plant cells, leading to dehydration. Plants rely on water for critical functions such as nutrient transport, photosynthesis, and maintaining turgor pressure.

Additionally, high salinity can also interfere with nutrient uptake. Essential nutrients may become chemically unavailable to plants, as they require a specific balance and concentration in the soil to be absorbed efficiently. The increase in osmotic stress caused by excess salts can lead to stunted growth, reduced yields, and in severe cases, plant death.

In contrast, high humidity can actually promote growth by reducing water loss from plant leaves through transpiration. An excessive water supply can also be beneficial up to a certain point, providing plants with the moisture they need for optimal growth. Similarly, optimized soil pH is crucial for nutrient availability and can enhance plant growth when maintained within the appropriate range for specific plant species.