Improvement of Graft Development in Tomato and Eggplant Grafted Cuttings by Supplying Warmed Water to Graft Union during Low-air-temperature Storage

Abstract

We investigated the effects of supplying warmed water to the graft union of tomato and eggplant grafted cuttings during low-air-temperature storage on graft development and plant growth after storage. The scions of grafted cuttings were held at an air temperature of 9 to 12°C, while the region from the cut end of the rootstock cuttings to the graft union was held at 12 to 37°C in water during 4 days' storage. The tensile strength of some cuttings' graft union was measured as an index of graft development. The tensile strength of the tomato graft union was much improved when the graft union temperature ranged from 23 to 27°C. That of the eggplant graft union increased as the temperature rose up to 29°C. After 4 days' storage, the remaining cuttings were planted in vermiculite medium and grown in a growth chamber. Cuttings from the temperatures that gave a higher tensile strength tended to grow larger. We also investigated the effects of supplying the water at 28°C to the graft union on the storage quality of cuttings by measuring the water status, gas exchange, and chlorophyll fluorescence parameters after 4 days' storage at an air temperature of 9 to 11°C. The leaf water potential and leaf conductance of scions with warmed graft unions were significantly higher than those with unwarmed graft unions. The chlorophyll fluorescence parameters Φ PSII and the electron transfer rate were maintained with warmed water during storage, but were significantly decreased without warmed water application. These results indicate that keeping the graft union warm during low-air-temperature storage can improve graft development, storage quality, and plant growth after storage.

Acclimatization of Cucumber (Cucumis sativus L.) Grafted Cuttings by Warming the Hypocotyl of the Rootstock in a Cold Chamber

“…Withered cotyledons were excluded from the leaf conductance and F v /F m measurements. The tensile strength of the graft union was measured after measuring leaf conductance and F v /F m , as described previously (Shibuya et al, 2007a). Fresh and dry weights of the scions were measured and used to estimate the water content.…”

“…This technology would also be effective for acclimatization because it can improve graft development and the quality of the rooting site with minimal loss of biomass (Shibuya et al, 2007a;Shimizu-Maruo et al, 2008). Because high illumination to enhance photosynthesis and high RH to reduce transpiration are less necessary at low air temperature, the warming approach could simplify and improve acclimatization.…”

“…My colleagues and I previously reported that warming tomato and eggplant grafted cuttings by supplying warm water to the graft union during low-air-temperature storage improves graft development, storage quality, and subsequent growth compared with those not warmed (Shibuya et al, 2007a. This technology would also be effective for acclimatization because it can improve graft development and the quality of the rooting site with minimal loss of biomass (Shibuya et al, 2007a;Shimizu-Maruo et al, 2008).…”

“…In this grafting method, the basal cut-end of a scion's hypocotyl is inserted into a hole drilled between the cotyledons of the rootstock. Previous studies (Shibuya et al, 2007a have only examined the warming treatment with splice-grafting of solanaceaous species to improve their storage. If the warming treatment could be applied to the acclimatization of grafted cucurbitaceous species, the use of this technology could be broadened, improving seedling production and reducing costs.…”

Exogenous auxin improves root morphology and restores growth of grafted cucumber seedlings

“…1a) to remove the roots (Davis et al 2008). Therefore, after grafting, the grafted cuttings must be transplanted into growing medium for rooting (Shibuya et al 2007).…”