Physiological and anatomical features of the silvering disorder of Cucurbita

SummaryLeaf silvering is a physiological disorder of marrows, Cucurbita pepo, exacerbated by drought. Silvered leaves had spaces between the upper epidermis and the mesophyll cells and within the mesophyll. The palisade cells were smaller and spongy mesophyll cells fewer. Completely silvered leaves contained 14% less chlorophyll per unit leaf blade area than green leaves. The rate of photosynthesis decreased as severity of silvering increased. The rate of photosynthesis was about 30% lower in the completely silvered than in the green leaves at saturating and above-saturating light and CO2. The results suggest that in silvered plants the CO2 absorption mechanism has been affected.