Involvement of endogenous gibberellins in the regulation of increased tomato shoot growth in solarized soil

Abstract

Environmental factors often affect plant growth bymodifying the levels of endogenous gibberellins (GAs).In this study, the involvement of GAs in theregulation of enhanced shoot growth in tomato (Lycopersicon esculentum Mill.) plants grown in soiltreated by solarization (a soil disinfestation method)was investigated. Seedlings at the cotyledonary stagewere transplanted into either solarized or untreatedcontrol soil. Plants in both soils grew free of anydisease symptoms. As soon as four days after planting,seedlings in solarized soil had a higher dry weightcompared to the control. Throughout most of theexperimental period of 18 days, leaf weight ratio washigher in the solarized vs. the control soil. Treatingshoot tips of control plants with 0.1 mg.L-1GA3 resulted in enhanced leaf and stem growth,thus reaching values similar to those of plants grownin solarized soil. The opposite effect was obtained bytreating plants grown in solarized soil with1 mg.L-1 uniconazole, a GA biosynthesisinhibitor. Quantitative GC-MS analyses revealed thatGA1 content in one and two-weeks old transplantsgrown in various solarized soils was up to 1.8 fold,and that GA3 content in two-weeks old plants wasup to five fold the values in the control. Theseincreases were linearly correlated with the increasein leaf dry weight. It was concluded that theincreased quantities of GA1, and eventuallyGA3, play a role in the increased growth oftomato shoots in solarized soil as early as seven daysafter transplanting.