• Document: Schneider, H The Anatomy of Citrus. In The Citrus Industry Vol II, Chapter 1, pp
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22 Schneider, H. 1969. The Anatomy of Citrus. In The Citrus Industry Vol II, Chapter 1, pp. 1-85.  Very extensive review of anatomy of citrus, but largely an original work  Purpose: Present comprehensive overview of citrus plant structure in classical plant anatomy format  How we will use this information!  How does anatomy relate to function?  What anomalies in anatomy and thereby function occur with biotic or abiotic stresses Scott, F. M., M. R. Schroeder and F. M. Turrell. 1948. Development, cell shape, suberization of internal surface, and abscission in the leaf of the Valencia orange, Citrus sinensis. Bot. Gaz. 109:381-411.  No comprehensive study of leaf development in citrus  Other plant leaves studied in relation to specific function  Purpose: Provide developmental picture in detail from primordium to abscission  (have interspersed Scott & Schneider figures, most of leaf from Scott et al) Arrangement of leaves, buds and petiole abscission zones on a summer shoot of citrus Aborted bud at termination of new shoot on citrus. No terminal bud growth, always second or first lateral bud Scott et al. : Leaf primordia and development at apical meristem of a citrus shoot Note vascular development of main vein Scott et al: Vascular system arrangement in a citrus leaf Vascular network forming in young leaf blade. Vascular network in citrus leaf – Scott et al: Note terminal net Vascular network and oil glands in a citrus leaf Leaf cross section Palisade parenchyma development – 2 layers, chloroplasts around wall? Initial development past primary wall Scott et al: Stomatal arrangement on lower surface of an orange leaf. Note guard cells, ante and substomatal chambers and plugged antechamber. Structure function – K pumps and pressure points WHY LOWER HALF? Two abscission zones? Limb structure phloem and cambium Rays? Vascular system in wood – phloem: sieve elements & companion cells K.F. Cossmann. 1939. Citrus roots: Anatomy, osmotic pressure and periodicity of growth. Palestine J. Bot., Rehovot Series. 3:65-103  Controversy as to existence of root hairs on citrus roots  Limited citrus species examined in earlier work  Purpose: Can conclusions about physiological function be made from root anatomy, particularly regarding physiological sheaths? Do citrus roots have root hairs? Development of primary and secondary vasular system in roots of citrus - Schneider Root has endodermis with casparian strip and xylem (phloem) strands developing above root cap Casparian strip infuses wall around endodermal cell walls preventing Solution solution passage flow through wall, must pass through cytoplasm Castle, W. S. 1978. Citrus root systems: Their structure, function, growth and relationship to tree performance. Proc. Int. Soc. Citriculture 1978; 62-69. Except for Cossmann, little reported about root structure in citrus Opportunity to use scanning electron microscopy Purpose: Review and observation of roots with SEM Rootcap Exposed, Root hairs sheared cortical cells Imbedded sand grain On the relationship between specific root length and the rate of root proliferation: a field study using citrus rootstocks. DAVID M. EISSENSTAT . New Phytol. (1991), 118, 63-68  This study tested two hypotheses:  (1) species with roots that have a high length to dry mass ratio or specific root length (SRL) also have the potential for high rates of root growth in small volumes of favourable soil and  (2) variation in average root diameter fully accounts for variation in SRL. M&M  The study used 13-year-old 'Valencia' sweet orange [Citrus sinensis (L.) Osbeck] trees budded to rootstocks representing a range of genotypes.  Soil cores 7-4 cm in diameter and 14-2 cm deep were extracted from beneath the canopy, and the soil was sieved free of roots and replaced.  Root length, diameter and dry weight of the roots in the disturbed soil and adjacent undisturbed soil were evaluated 5, 10, 19 and 40 weeks following soil replacement. Results  Averaged across rootstocks, root length density increased in a linear fashion in the disturbed soil and was comparable to that in the undisturbed soil by 40 weeks.  Mean root diameter of the fibrous roots ( < 2 mm) declined with age.  Rootstocks with the highest SRL had the most rapid rate of root proliferation (cm cm"^ wk"^) (r = 0-94) and the greatest rate of water extraction at 19 weeks (r = 0 79). Figure 1. Time course of (a) root length density and {b) mean root diameter of the fibrous roots, averaged across six citrus rootstocks, in disturbed and adjacent undisturbed soil. Roots were sampled at 5, 10, 19 and 40 weeks

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