FLOODING EFFECTS: SHOOTS

I. INTRODUCTION

A. Messages: positive, negative, accumulative

B. Substances: water, photosynthate, hormones, toxins, nutrients

II. INHIBITION OF GROWTH

A. Inhibition of leaf growth (water stress)

B. Inhibition of stem extension (gibberellin, toxins, water stress, assimilate deficiency, nutrient deficiency)

C. Inhibition of photosynthesis (stomates close, carboxylating enzyme inhibited)

III. PROMOTION OF EXTENSION GROWTH

A. Occurs in aquatics

B. Cell wall extension caused by ethylene

IV. HYPERTROPHY

A. Induced by rising water

B. May be result of increase in ethylene, photosynthate and auxin at plant base

V. ADVENTITIOUS ROOTING

A. Occurrence (arise from stem when original roots die)

B. Adaptive significance

C. Adaptive features

D. Causes (probably same as for hypertrophy)

VI. REORIENTATION OF GROWTH

A. Epinastic curvature of leaf petioles

B. Vertical growth of stolons

VII. SENESCENCE

A. Occurrence (accellerated by flooding)

B. Negative messages (N)

C. Positive messages (P, Fe, H₂S)

VIII. ABSCISSION

A. Senescing tissue produces ethylene

B. Produces little auxin, which would inhibit ethylene

IX. WILTING

A. Root permeability quickly decreases upon flooding, causing wilting

B. May be relieved by stomatal closure

C. Root permeability rapidly increases when roots die, relieving wilting