Leaf Photosynthesis and Transpiration of Two Leek Cultivars With Differing Pseudostem Pungency Levels

Abstract

The effects of temperature on leaf photosynthesis and transpiration were investigated for two leek (Allium porrum L.) cultivars that showed differing pseudostem pungencies, when grown in a controlled greenhouse environment. Basal sections of 20 week old cv. Tadorna were shown to be nearly four times as pungent as those of cv. Ramona. Greenhouse climate data indicated 37% of weekly average temperatures were above 25°C, approaching the temperature at which leek growth is inhibited. Due to the environmental influence of temperature on tissue pungency, leaf gas exchange was measured at 20°C and 27°C to see if the gas exchange characteristics of the cultivars differed as well. The net carbon exchange rate (NCER) and leaf transpiration of cv. Ramona remained relatively steady over the photoperiod at both 20°C and 27°C, but were reduced by the increased temperature. In comparison, NCER and leaf transpiration of cv. Tadorna were greatly reduced by elevated temperature during the morning and early afternoon periods. Gas exchange of mature and immature leaf tissue was also measured. Immature leaves of cv. Tadorna had lower NCER and displayed a significant decline in photosynthesis and transpiration during the photoperiod. Despite having reduced productivity under the greenhouse conditions, Tadorna displayed higher tissue pungency upon maturity.

S-Alk(en)yl- l-cysteine Sulfoxides and Relative Pungency Measurements of Photosynthetic and Nonphotosynthetic Tissues of Allium porrum

“…The leek (Allium porrum L.) is our model Allium species, since it is closely related to onions and garlic. However, unlike the tubular leaves of onions, the flat and firm leaves of leeks are more suitable for photosynthetic studies coupled to flavor precursor analysis (19). However, a comprehensive analysis of the RCSOs found in this species is currently not available.…”