Effect of Defoliation or Excision of Growing Axillary Shoots on the Composition of Labeled Products of Photosynthesis in the Leaves and Xylem Sap of Kidney Bean

Abstract

The content of 14 C in the products of photosynthesis of the source leaf and xylem sap was investigated in kidney bean ( Phaseolus vulgaris L.) plants during the stage of mass tillering. 14 C partition was measured a day after two-minute photoassimilation of 14 ëé 2 by an individual mature leaf located in the middle part of the shoot. The source-sink relations were disturbed by the excision of all mature leaves (except the source leaf) or all growing axillary shoots. The leaves or growing axillary shoots were excised 15 min after leaf feeding with 14 ëé 2 . A day later, in plants with excised growing axillary shoots, the content of 14 C in the source leaf was by 18% higher and in those with removed leaves by 15% lower than in control plants. The next day after the excision of growing axillary shoots, radioactivity of the xylem sap increased; after defoliation, both the volume of the xylem sap and its specific radioactivity decreased. In the xylem sap of defoliated plants, the proportion of 14 C in malate decreased more than six times, whereas the proportion of 14 C in amino acids somewhat increased (1.5 times). In two days, the volume of the xylem sap exuded by treated plants became the same as in control plants and its radioactivity decreased almost by an order of magnitude but essentially did not differ in the both types of treatment. It is concluded that the processes occurring in the roots are governed by photosynthesis but its regulatory effect is limited by a photoperiod and largely depends on changes in the ratio between biosynthesis of amino acids in the roots and leaves.

Reproduction and probing behaviour of the bird cherry‐oat aphid Rhopalosiphum padi on detached leaves and leaves on intact seedlings of the winter host, bird cherry Prunus padus

“…In addition, most of the amino acids and ions in leaf tissue have a diurnal variation in concentration, with the highest concentrations during the day (Yarwood, 1946) when the leaves are normally detached for experiments. In some plants, concentrations of free amino acids increase after leaf excision (Montllor et al , 1990; Chikov et al , 2005). Leaf excision can cause water loss and wilting (Reymond et al , 2000), although several studies suggest that excised leaves may maintain water content unless held in dry environments (Yarwood, 1946; Savage et al , 1984).…”

Kiwi 4.0: In Vivo Real-Time Monitoring to Improve Water Use Efficiency in Yellow Flesh Actinidia chinensis

“…We showed that the bioristor sensors enabled the detection of defoliation. This is supported by the analysis of the daily sensor response that was continuously reduced in intensity in both FI and MI (Figure 4) as a result of the reduced volume of the xylem sap [35] triggered by defoliation, together with a strong reduction in the whole-plant photosynthesis (Figure 5).…”

Do Larvae of Bertha armyworm, Mamestra configurata (Walker) (Lepidoptera: Noctuidae), express induced feeding responses?

“…Plant responses to herbivory can result in increases in toxic or deterrent metabolites (Karban and Baldwin 1997), but alternatively, excised tissues often have higher levels of free amino acids than intact tissues (Montllor et al. 1990; Chikov et al. 2005).…”