Maximum Yield USA July 2017 | Page 60

calcium nutrition How to Boost Calcium Nutrition in Hydroponics 58 feature increases transpiration from the foliage.” calci Since transpiration and calcium flow within the plant is so heavily influenced by the environment, lowering humidity and increasing airflow across the foliage assists with boosting moisture loss and calcium incorporation into new cells. However, while lowering humidity from high levels does boost transpiration, a very low humidity can result in other problems. Very low humidity increases transpiration from the foliage, particularly of large leafy plants, so that the calcium carried in the transpiration stream is rapidly deposited in the lower leaves of the plant, leaving insufficient amounts to make it to the tops of the plant. Since leaves have many stomata, they have a higher rate of transpiration that attracts proportionally more calcium than fruit or flowers, which have very few stomata (and hence a low rate of transpiration to draw in calcium). In extreme cases of low humidity, particularly during the warmest part of the day, the transpiration rate is pushed so high that the plant comes under water stress, a condition that restricts calcium-rich water flow in the xylem and up into the plant. Maintaining the correct humidity levels, particularly when plants are grown in warm conditions that favor high rates of tissue development, becomes an important aspect of optimizing calcium nutrition. “ VERY LOW HUMIDITY