Pereskiopsis diguetii

Name and assimilatory organs

POWO accepts Pereskiopsis diguetii (F.A.C.Weber) Britton & Rose. Synonyms include P. spathulata and P. velutina. The physiological material was described as having small, flat, fleshy leaves persisting on relatively thick, hard shoots. Leaves and the green stem remain photosynthetically active. [2-WWW] [Martin and Wallace 2000]

Rytm fotosyntezy

In Martin and Wallace's experiment, the maximum rate of leaf CO₂ uptake greatly exceeded that in stems alone. Leafy shoots took up more carbon during the day than at night, with strongly reduced assimilation around midday and a renewed increase in late afternoon. Material was maintained at 30/20°C under a fourteen-hour day. [Martin and Wallace 2000]

Stems alone had a proportionally greater contribution from nocturnal assimilation. Acidity also increased at night in both organs. Comparison of acid balance with gas exchange demonstrated a contribution from internal CO₂ recycling. This gives a physiological picture with three components, daytime carbon fixation, nocturnal uptake and reuse of respiration products. [Martin and Wallace 2000]

Significance of leaf retention

Strong leaf activity explains why foliage condition is a significant feature of material in growth studies. Comparing a leafy shoot with a defoliated stem separates the contributions of the two organs. Experimental data show their complementary functions and should be related to the particular developmental phase and hydration conditions. [Martin and Wallace 2000]