Adventitious root formation ‘in vitro’ in apple rootstocks (Malus pumila) II. Uptake and distribution of indol‐3yl‐acetic acid during the auxin‐sensitive phase in M.9 and M.26

Abstract

During the auxin‐sensitive phase of root initiation, rates of 3‐indolyl‐ [2‐14C] acetic acid (IAA) uptake into the 1 cm bases of shoots of the apple rootstock M.9 (Malus pumila Mill.) ‘in vitro’ were not significantly affected by the presence of 10−3M phloroglucinol (PG) using either liquid or agar‐solidified media. The use of a liquid medium did however reduce rates of uptake over a 10‐day period of auxin application. The distribution of labelled IAA between the 1‐cm base and the shoot remainder was not affected by PG. Exposure of shoots of the difficult‐to‐root M.9 and the easy‐to‐root M.26, to 2.8 × 10−5M IAA containing [2‐14C] IAA revealed no positive correlation between the amount of label taken up by the 1‐cm base and rooting performance. M.9 bases absorbed almost twice as much label as M.26 after 9 days but had produced only one‐third as many roots. Measurements of label distribution between the 1‐cm base and the shoot remainder showed that less than 10% of the label moved to the shoot remainder over a 6‐day period of auxin application. Dose‐response curves of IAA and rooting over the range 1 × 10−5M and 3 × 10−3M showed that root number in M.9 was at an optimum at 1 × 10−3M IAA after 6 days whilst M.26 required only 1 × 10−4M for a similar response. These data support the hypothesis that differences in rooting of the two rootstocks reflect differences in the endogenous metabolism of exogenous IAA and not differences in its rates of uptake or distribution in the shoots.

L-arginine impact on cherry rootstock rooting and biochemical characteristics in tissue culture

“…It may also be the result of the conversion of the IBA exogenously applied to IAA, as demonstrated by Epstein and Lavee (1984) in olive (Olea europaea) and in stem cuttings of grapevine (Vitis vinifera). Another explanation according to James (1983b) may be the different rates of metabolism and degradation of the applied auxin IBA. However, we cannot anticipate the possibility that IBA can be transformed into another compound at a similar rate in both rootstocks.…”

“…The different response of the 2 rootstocks to the exogenous application of IBA and therefore their differences in rooting ability may be the result of differences in the levels of the endogenous auxin IAA (Le, 1985), auxin metabolism Thurnbon, 1981a, 1981b;James, 1983b), or sensitivity of cells, targets of the auxin (James, 1983a). It may also be the result of the conversion of the IBA exogenously applied to IAA, as demonstrated by Epstein and Lavee (1984) in olive (Olea europaea) and in stem cuttings of grapevine (Vitis vinifera).…”

Relationship between Indole-3-Acetic Acid Levels in Apple (Malus pumila Mill) Rootstocks Cultured in Vitro and Adventitious Root Formation in the Presence of Indole-3-Butyric Acid

“…The differential response of M.26 and M.9 to exogenous auxin applications has led investigators to suggest that differences in rooting ability between M.9 and M.26 result from differences in endogenous auxin levels (16), auxin metabolism (11,13,14), or sensitivity of target cells to auxin (10). The objective of this research was to examine the relationship between endogenous IAA levels of M.26 and M. 9 shoots cultured in vitro and the rooting response of shoots to exogenous auxins.…”

In vitro rooting and biochemical parameters in the cherry rootstocks CAB-6P and Gisela 6 using L-methionine

“…In our study, when IBA was applied exogenously to the 2 rootstocks there was a different reaction to the rooting ability of each, due perhaps to the differing levels of endogenous IAA (Le 1985), auxin metabolism Thurbon 1981a, 1981b;James 1983b), or sensitivity of cells -targets to the auxin (James 1983a). Other explanations could be that the exogenously applied IBA is converted to IAA as demonstrated by Epstein and Lavee (1984) in olive (Olea europaea) and in the stem cuttings of grapevine (Vitis vinifera), or it might be the different rates of metabolism and degradation of the applied auxin IBA (James 1983b).…”

“…Other explanations could be that the exogenously applied IBA is converted to IAA as demonstrated by Epstein and Lavee (1984) in olive (Olea europaea) and in the stem cuttings of grapevine (Vitis vinifera), or it might be the different rates of metabolism and degradation of the applied auxin IBA (James 1983b). Nevertheless, we cannot rule out the possibility that IBA can be transformed into another compound of similar rate in both rootstocks; however, there was a difference in the rate of complexing conjugation with amides or esters.…”