HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Volenec, J. J. Search for Related Content PubMed Articles by Volenec, J. J. Agricola Articles by Volenec, J. J.

Herbage Growth and Carbohydrate Metabolism of Diploid and Tetraploid Alfalfa

Dep. of Agronomy, Purdue Univ., West Lafayette, IN 47907

Polyploidy influences growth of alfalfa (Medicago sativa L.), but its impact on shoot and root carbohydrate metabolism and subsequent herbage regrowth rate remains unclear. This study related differences in herbage growth between isogenic diploid (2x) and tetraploid (4x) alfalfa populations to concentrations of root total nonstructural carbohydrates (TNC) and nonstructaral carbohydrate pools and dark respiration rates (RD) of meristematic shoot tissues. Leaf area, herbage weight, and taproots of plants were obtained weekly during 4 wk of regrowth in a controlled environment. Leaf area per plant and relative leaf area growth rate were approximately 100 and 33% greater, respectively, in the 4x population than in the 2x population. Although more herbage accumulated on 4x plants, herbage relative growth rates of populations were similar between Days 7 and 14, averaging 0.27 kg kg^–1 d^–1. Differences in shoot growth were not related to Ra of shoot tip tissues, which averaged 55.2 ümol O₂ mkg^–1 s^–1, or concentrations of glucose, sucrose, and starch in shoot tips. Root TNC concentrations of 2x and 4x populations were similar, initially averaging 360 g kg^–1 dry wt. Concentrations of TNC increased in a linear fashion in roots of both populations during regrowth. The greater amount of shoot tissue present in the crown immediately following defoliation, along with the larger mass of individual growing shoot tips, contributed to more rapid leaf area development and faster herbage regrowth of the 4x population than the 2x population.

Key Words: Medicago sativa L. • Relative growth rate • Relative leaf area growth rate • Shoot elongation rate • Dark respiration • Ploidy • Total nonstructural carbohydrates

Received for publication March 23, 1987.