###### Abstract  
Use of leaf gas exchange measurement enhances the characterization of growth, yield, physiology, and abiotic stress response in grapevines. Accuracy of a crop response model depends upon sample size, which is often limited due to the prolonged time needed to complete gas exchange measurement using currently available infra-red gas analyzer systems. In this experiment, we measured mid-day gas exchange of excised and _in situ_ leaves from field grown wine grape (_Vitis vinifera_) cultivars. Depending upon cultivar, we found measuring gas exchange on excised leaves under a limited time window post excision gives similar accuracy in measurement of gas exchange parameters as _in situ_ leaves. A measurement within a minute post leaf excision can give between 96.4 and 99.5% accuracy compared to pre-excision values. When compared to previous field data, we found the leaf excision technique reduced time between consecutive gas exchange measurements by about a third compared to _in situ_ leaves (57.52 \(\pm\) 0.39 s and 86.96 \(\pm\) 0.41 s, for excised and _in situ_, respectively). Therefore, leaf excision may allow a 50% increase in experimental sampling size. This technique could solve the challenge of insufficient sample numbers, often reported by researchers worldwide while studying grapevine leaf gas exchange using portable gas exchange systems under field conditions. CO2 assimilation rate; stomatal conductance; measurement time; photosynthetic decline curve; infra-red gas analyzer +
Footnote †: journal: Applied  
had to move potted plants to access their leaves for leaf gas exchange measurements. Consequently, to measure leaf level gas exchange under field conditions researchers have resorted to modifying devices [9; 10; 11] and sampling techniques [7]. The ability of leaf tissue to retain water after a leaf is excised has been previously studied in laboratory conditions in wheat (_Triticum aestivum_) [12], and cotton (_Gossypium hirsutum_) [13]. Furthermore, photosynthetic decline curves post leaf excision have been studied under laboratory conditions in corn (_Zea mays_) [14]. Photosynthetic recovery post water stress has also been studied in grapevines (_Vitis vinifera_) using excised leaves [15]. Due to the ability of a leaf to remain turgid for a period of time after being excised [3; 14], photosynthesis for an excised leaf may not substantially decline for a period after excision. This period could be used to increase the number of leaves sampled and measured for gas exchange in experiments conducted in the field or greenhouse. Previous researchers have excised leaves to study various plant characteristics [16; 17]. Excised leaves have been used to study photosynthetic carbon assimilation (\(A_{\text{n}}\)) in wheat (_Triticum aestivum_) [18], grapevines (_V. vinifera_) [15], sorghum (_Sorghum bicolor_) [19] and peas (_Pisum sativum_) [20] under laboratory conditions. In addition, [PERSON] et al. (2019) [21] used leaf chlorophyll fluorescence imaging to perform high throughput phenotyping for photosynthetic and photo-protective parameters in wheat using excised leaves. This method enabled them to study more than 500 samples each day. To measure leaf gas exchange in grapevines, researchers generally measure photosynthesis on attached leaves [22; 23], and move measurement devices from leaf to leaf, and plant to plant. Although several studies have incorporated leaf excision to characterize physiological parameters in various plant species under laboratory conditions [15; 18; 21], there is still a lack of information on using leaf excision techniques when facing logistical challenges estimating grape leaf gas exchange in field settings.