Strategies of Phloem Loading

Abstract

CONTENTS INTRODUCTION 253 DEFINITION OF STEVE ELEMENT LOADING AND PHLOEM LOADING 254 ULTRASTRUCTURE OF THE SIEVE ELEMENT LOADING ZONE ... 255 STRUCTURE OF THE PHLOEM LOADING ZONE 256 LOADING AND TRANSPORT SECTIONS OF THE PHLOEM IN THE VEIN SYSTEM. 258 POTENTIAL PATHWAYS OF PHLOEM LOADING .. , ,......... 259 PATHWAY OF PHLOEM LOADING AND COMPOSITION OF THE PHLOEM SAP.... . . 261 LIMIT A TIONS OF THE EXPERIMENTAL APPROACHES IN IDENTIFYING PHLOEM LOADING MECHANISMS ....... ...... ... ... 262 PHYSIOLOGICAL EVIDENCE FOR DIFFERENT MODES OF PHLOEM LOADING ..... 264 COMPANION CELL ULTRASTRUCTURE AND MODE OF PHLOEM LOADING ......... 265 MECHANISM OF SYMPLASTIC PHLOEM LOADING .. 266 MECHANISM OF APOPLASTIC PHLOEM LOADING . . . . .. 268 Sugar Release from the Mesophyll Symplast ........ .. ,,. 269 The Apoplastic Passage Compartment ...... , .. .. .. .. ,, .. ,,..... 271 Sugar Uptake by the SE/CC-Complex Symplast ........ ...... ...... .... 272 MOLECULAR EXAMINATION OF THE SUCROSEIPROTON SYMPORT 273 TRANSPORT EFFICIENCY OF DIFFERENT MODES OF PHLOEM LOADING 274 ECOPHYSIOLOGICAL CONCEPT OF PHLOEM LOADING 275