Spontaneous Phloem Bleeding from Cryopunctured Fruits of a Ureide-Producing Legume

Abstract

The vasculature of the dorsal suture of cowpea (Vigna uagwicalata IL.] Walp) fruits bled a sugar-rich exudate when punctured with a fie needle previously cooled in liquid N2. Bleeding continued for many days at rates equivalent to 10% of the estimated current sugar intake of the fruit. A phloem origin for the exudate was suggested from its high levels (0.4-0.8 millimoles per milliliter) of sugar (98% of this as sucrose) and its high K' content and high ratio of Mg2e to Ca2l. Fruit cryopuncture sap became labeled with 14C following feeding of I'jqurea to leaves or adjacent walls of the fruit, of '4CO2 to the pod gas space, and of I1'4C asparagine or '4Callantoin to leaflets or cut shoots through the xylem.Rates of translocation of 14C-assimilates from a fed leaf to the puncture site on a subtended fruit were 21 to 38 centimeters per hour. Analysis of '4C distribution in phloem sap suggested that I'4Caflantoin was metabolized to a greater extent in its passage to the fruit than was 1'Cj to puncture the vascular strands of the mid-dorsal suture of a fruit with the tip of a fine (0.5-mm) needle previously cooled in liquid N2, retaining the needle tip in the fruit for a period of 5 s to allow chilling of tissues in the immediate vicinity of the puncture. This treatment induced bleeding usually within 30 min ofpuncture and by placing microcapillaries (1-5 Ml capacity) over the wound, the exudate was readily collected. Collection periods ranged from 30 min to several days depending on the nature of the experiment. Time courses of bleeding (labeled or unlabeled sap) from single sites were followed by regularly changing microcapillaries trapping the exuded sap. Cryopuncturing of fruits was attempted day and night on fruits aged 6 to 18 d after anthesis. Sap collected over several hours of bleeding from 30 or more similar fruits was combined to provide samples of 0.5 to 1.5 ml, enabling a variety ofanalyses to be conducted on a single sap sample.

Within-plant variation in concentrations of amino acids, sugar, and sinigrin in phloem sap of black mustard,Brassica nigra (L.) Koch (Cruciferae)

“…Second, the estimates in the present study compare favorably with values obtained in other studies. The estimated concentrations of amino acids in the phloem sap of black mustard (77-216 mM) (Table 3) are similar to those measured in the phloem sap of a variety of herbaceous plant species (112-1600 mM) (Barlow and Randolph, 1978;Fukumorita and Chino, 1982;Pate et al, 1984;Fisher and Gifford, 1986;Weibutl, 1988). Similarly, estimated sugar concentrations (19.1-25.8%) ( Table 3) fall within the range recorded in herbaceous plants (4.3-30.8%) (e.g., Pate, 1973;Pate et al, 1974;Fukumorita and Chino, 1982;Fisher and Gifford, t986;Ohshima et al, 1990).…”

Distribution and Metabolism of Xylem-Borne Ureido and Amino Compounds in Developing Soybean Shoots

“…Here, as suggested earlier ( 17), the major xylem-borne nitrogenous solutes, ALA and ALA, were readily metabolized (Table III), and the extent of direct xylem-to-phloem transfer remained uncertain. In cowpea, a species that also exports principally ureides from root nodules, investigations using aphids (3) and cryopunctured fruits (16) Previous research has shown that the concentration of xylem-borne amino acids is an important factor in the uptake and distribution pattern in tomato (22) and cottonwood (23) stems. Therefore, we supplied ureido and amino compounds at high specific activity against the background of the solutes that are normally delivered from nodulated roots to shoots in the xylem stream.…”

Utilization of Nitrate for Early Androgenic Embryogenesis of Brassica napus L.

“…The media contained a high concentration (0.38M) of sucrose and glutamine which were known to stimulate androgenesis in anther culture (Keller et al,1975) and potassium nitrate as a presumed source of nitrogen. On the other hand, the exudate of cowpea fruits from phloem origin contained 0.4-0.8 M of sucrose (Pate et al, 1984). Recently, Ilic-Grubor et al (1998b) Other components were the same as those in NLN-13 medium (Keller et al,1987).…”