著者

Hiroshi Matsuda Hiroo Takaragawa

出版者

The Japanese Society for Horticultural Science

雑誌

The Horticulture Journal (ISSN:21890102)

巻号頁・発行日

pp.QH-060, (Released:2023-06-17)

被引用文献数

2

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Passion fruit (Passiflora spp.) vines, mostly indigenous to tropical highlands, although some species can be cultivated in tropical lowlands, are susceptible to high temperatures. To increase the resilience of passion fruit to the warming climate, there is an urgent need to evaluate existing genetic resources for traits suited to high temperatures and to efficiently select the superior genotypes. We investigated the genotypic variation in leaf photosynthetic reduction at high temperatures (> 30°C) as a base target trait for warming climates. Leaf photosynthesis and dark respiration were measured at 30–45°C leaf temperatures for 13 genotypes from various Passiflora spp. using a portable gas exchange system. Temperature-net and -gross photosynthetic rate curves were plotted, and the relationships between the photosynthetic rate and the transpiration rate and stomatal conductance were analyzed. The net photosynthetic rate decreased with reduced stomatal conductance and transpiration rate as the leaf temperature increased from 30°C to 40°C. Up to 45°C, the net photosynthetic rate continued decreasing with increasing dark respiration rate, whereas the gross photosynthetic rate tended to stop decreasing as the stomatal conductance and transpiration rate stopped decreasing. The respiration load of photosynthesis varied among genotypes: Alata seedling #1 (P. alata) and ‘MaQuatro’ (P. edulis f. flavicarpa) showed the lowest load, together with the smallest reduction in photosynthetic rate at high temperatures, while the Iriomote strain (P. laurifolia) showed the largest load despite the smallest reduction in photosynthetic rate. Although the trend in the physiological response to high temperatures was similar among genotypes, the rate of leaf photosynthetic reduction at high temperatures varied among passion fruit genotypes both inter- and intra-specifically. Reduction of the photosynthetic rate at high temperatures was significantly correlated with stomatal activity under non-stress conditions at 30°C leaf temperature. Stomatal length was closely correlated with photosynthetic and transpiration rates at higher leaf temperatures in the P. edulis group, whereas no correlation was detected when including the lowland relatives. We concluded that genotypes showing higher stomatal conductance and transpiration rates at 30°C leaf temperature maintained a higher leaf photosynthetic rate at temperatures > 40°C, providing potential indicators for screening.