Development of the vascular system in the leaf of barley (Hordeum vulgare L.)

• Published in: International journal of plant sciences 1994-03, Vol.155 (2), p.143-157
• Main Authors: Dannenhoffer, J.M, Evert, R.F
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; ANATOMIA DE LA PLANTA; ANATOMIE VEGETALE; Anatomy; Barley; Biological and medical sciences; Cardiovascular system; CELL DIFFERENTIATION; CELLS; CELLULE; CELULAS; Corn; Development; Developmental biology; DIFERENCIACION CELULAR; DIFFERENCIATION CELLULAIRE; Economic plant physiology; FEUILLE; Fundamental and applied biological sciences. Psychology; Grain; Growth and development; HOJAS; HORDEUM VULGARE; LEAF PRIMORDIA; LEAVES; Morphogenesis, differentiation, rhizogenesis, tuberization. Senescence; Phloem; PLANT ANATOMY; Plant growth; Plant growth. Development of the storage organs; Plant physiology and development; PLANT VASCULAR SYSTEM; Plants; Sieve tubes; SISTEMA VASCULAR DE LA PLANTA; SYSTEME VASCULAIRE DES PLANTES; Vegetative apparatus, growth and morphogenesis. Senescence; Xylem
• ISSN: 1058-5893; 1537-5315
• DOI: 10.1086/297153

The development of the vascular system in the leaf of barley, Hordeum vulgare L., was studied from its inception to maturity. Young primordia were examined with the scanning electron microscope, and distinctive early morphological stages of primordium development were correlated with the initiation of the longitudinal procambial strands. All longitudinal procambial strands originate in isolation, without continuity with the previously existing stem vasculature. The first-formed strands, which have large-bundle anatomy in both blade and sheath of the mature leaf, arise in the disk of insertion (the stem segment associated with the primordium) and from there develop acropetally into the free portion of the primordium and basipetally into the stem below. Subsequently formed strands arise in the primordium. These strands are interpolated between older strands across the width of the primordium in a precise order, and they appear to develop both acropetally and basipetally. By the time the young leaf is 4 mm long, all of its longitudinal procambial strands have been initiated; in addition, the ligule has been initiated, delimiting blade from sheath. The first protophloem and protoxylem elements of the large strands arise in the disk of insertion near the site of initiation of each strand, the protophloem in advance of the protoxylem. From the site of initiation, the protophloem and protoxylem develop acropetally into the primordium and basipetally into the stem, where, at a later stage of development, they interconnect with phloem and xylem in the nodal region of the leaf two nodes below. During further leaf growth, three successive regions can be identified within the blade: (1) a distal, mature region in which elongation has ceased and metaphloem and metaxylem elements are differentiating basipetally in all strands, (2) a region in which elongation is occurring and protophloem and protoxylem elements are mature or nearly mature but in which metaphloem and metaxylem elements have not yet begun to differentiate, (3) a region in which cell division is occurring and some protophloem and protoxylem elements are still differentiating.