Diurnal Changes of the Exudation Rate and the Mineral Concentration in Xylem Sap after Decapitation of Grafted and Non-grafted Cucumbers

Abstract

SummaryThe xylem sap in cucumbers (Cucumis sativus L.) which were or were not grafted onto figleaf gourd (Cucurbita ficifolia Bouche) was collected after decapitation from the cut end of the stems hourly. The exudation rate was highest in the first one hour collection regardless of grafting, and then decreased rapidly with time. However, there was a diurnal change in the exudation rate with the maxima occurring at 1 : 00 to 3 : 00 PM and the minima at 7 : 00 to 8 : 00 AM, irrespective of decapitation time. The grafted cucumbers were smaller in amplitude than the nongrafted ones.The rate of xylem exudation and the concentrations of N03-N, P, Ca and Mg in the first one hour exudate were higher in the grafted cucumbers than in the nongrafted ones.Only the K concentration was higher in the non-grafted cucumbers. The mineral concentration in the exudate changed remarkably with time after decapitation ; the N03-N, K and Ca concentrations decreased and the P concentration increased rapidly for the first several hours.The Mg concentration scarcely changed. Thereafter, the N03-N and K concentrations of the exudate in the grafted cucumbers fell below the N03-N and K concentrations in the nutrient solution, while in the non-grafted cucumbers the former was kept always above the latter. From these results, the grafted cucumbers were considered to be superior to the non-grafted ones, in water uptake and nutrient absorption except for K and also to depend more intensely in N03-N and K absorptions on some metabolities from the upper parts of the plants.

Leaf Gas Exchanges and Mineral Ion Composition in Xylem Sap of Iranian Melon Affected by Rootstocks and Training Methods

“…These results indicate that the pattern of mineral absorption in 'Khatooni' was markedly influenced by the type of rootstocks and training methods used. Similar results have been reported with other crops grafted onto different rootstocks (Masuda, 1989;Masuda and Gomi, 1982). In the present study, the rate of exudation from grafted plants was higher than the nongrafted ones.…”

Daily variations of xylemic exudation rate in tomato

“…Many authors have reported diurnal variations of xylemic exudation in numerous species (17,10,13,3,11). A cyclic variation of exudation in the tomato cultivar "Groseille rouge" (Lycopersicum racemingerum) has been observed (12) whose periodicity was 12 h with two maxima, at midday and at midnight.…”

“…Cyclic variations of exudation rate has also been observed for several days after detopping with a gradual decrease of the oscillations. (17,13,11).…”

Xylem Flow Rate Differences Are Associated with Genetic Variation in Snap Bean Pod Calcium Concentration

“…Studies of xylemic exudation in tomato (Lycopersicum esculentum Mill.) (Ferrario et al, 1992), tobacco (Nicotiana tabacum L.) (Wallace et al, 1966), corn (Zea mays L.) (Canny and McCully, 1988;van de Geijn and Smeulders, 1981), and cucumber (Cucumis sativus L.) (Masuda and Gomi, 1982) have shown that rates and compositions of exudates are different among species. Root pressure provides sufficient Ca to nontranspiring tissue such as cabbage (Brassica oleracea L.) heads (Palzkill and Tibbitts, 1977;Tibbitts and Palzkill, 1979) and strawberry (Fragaria ×ananassa Duch.)…”