Open Access(430) Leaf Gas Exchange of Carrots in Response to Increasing Leaf Temperatures
Author(s) -
F. Christine Pettipas,
Rajasekaran R. Lada,
Robert J. Gordon,
Tess Astatkie
Publication year - 2005
Publication title -
hortscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.518
H-Index - 90
eISSN - 2327-9834
pISSN - 0018-5345
DOI - 10.21273/hortsci.40.4.1075d
Subject(s) - photosynthesis , transpiration , stomatal conductance , cultivar , carboxylation , water use efficiency , daucus carota , horticulture , chemistry , carbon dioxide , botany , zoology , biology , biochemistry , organic chemistry , catalysis
Increasing temperature as a result of global climate change is expected to exert a great influence on agricultural crops, possibly through effects on photosynthesis. Response to temperature of leaf gas exchange parameters of carrot ( Daucus carota L. var. sativus ) cultivars Cascade, Carson, Oranza, and Red Core Chantenay (RCC) were examined in a controlled growth room experiment. Leaf net photosynthetic rate (P N ), stomatal conductance (g s ), and transpiration rate (E) were measured at temperatures ranging from 15 to 35 °C at 370 μmol·mol -1 (CO 2 ) and 450±20 μmol·m -2 ·s -1 PAR. The cultivars responded similarly to increasing temperature and did not differ in most photosynthetic parameters except g s . The P N increased between 20 and 30 °C, thereafter increasing only slightly to 35 °C. On average, increasing temperature from 20 to 30 °C increased P N by 69%. Carboxylation efficiencies (Ca/Ci ratio) ranged from 1.12–2.33 mmol·mol -1 while maximum P N were 3.25, 3.90, 5.49, 4.19 μmol·m -2 ·s -1 for Carson, RCC, Cascade, and Oranza, respectively. The E did not reach maximum at 35 °C while g s peaked at 30 °C and then decreased by 93% at 35 °C. The water use efficiency (WUE) decreased with an increase in temperature due to increases in both P N and E. The results indicate that increasing temperatures above the seasonal average (<20 °C) increases both P N and E up to 30–35 °C. An increase in photosynthesis due to an increase in temperature is expected to hasten growth. Carrots may be able to withstand a moderate increase in temperature.