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FREQUENCY AND GROUPING OF VESSEL ENDINGS IN ALFALFA ( MEDICAGO SATIVA ) SHOOTS *
Author(s) -
WIEBE H. H.,
GREER R. L.,
ALFEN N. K.
Publication year - 1984
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1984.tb03622.x
Subject(s) - vascular bundle , plant stem , biology , botany , petiole (insect anatomy) , medicago sativa , anatomy , abscission , free nerve ending , vascular tissue , hymenoptera
S ummary Vessel endings in various parts of the alfalfa ( Medicago sativa L.) shoot were mapped by an India ink movement method. Stems were excised at various locations between the fifth and sixth nodes below the apex and placed in vials of India ink. Vessel endings were determined by examining the distance to which ink penetrated in the transpiration stream; the particles of India ink are too large to pass from vessel to vessel through pit membranes. The highest frequencies of vessel endings were found (1) in the petiolules and blades of the leaflets, (2) in the pulvinus of the petiole where the leaf traces emerge from the stem and anastomose while traversing the abscission zone, and (3) in the stem nodes where leaf traces arise and vascular bundles anastomose. The frequency of vessel endings was low and uniformly distributed throughout both internodes and petioles. Vessels were longest in the internodes and shortest in the leaflets. The regions where vessel endings were grouped coincided with those determined in other studies to be particularly susceptible to vascular blocking by macromolecules such as those produced by vascular wilt pathogens.