HUMIC ACID EFFECT ON THE STOMATA CONDUCTANCE AND LEAF ABSCISSION ON APPLE CV. GOLDEN DELICIOUS UNDER TROPICAL CONDITIONS.

One of the main problems of growing apples in subtropical conditions in Mexico: is the initiation to the rest.
Under those conditions the leaves remains on the trees causing uneven and low bud break.
In order to solve tis problem a experiment was performed with CuSO₄ mixed with humic acid (Humitron). The hypothesis is that the acid will stimulate the stomata opening and then facilitate the entrance of CuSO₄. The experiment was established in the greenhouse and in the field with trees five years old.
The humic acid doses was 0, 2 and 4%, all the treatments were mixed with 2% CuSO₄. After the spray the stomata opening was increased in a linial manner according with the acid doses.
Defoliation with only CuSO₄ was in the order of 20% whereas the mixed CuSO₄ and humic acid start leaf absission after 7 days of application, reaching a maximum of 90%. It is suggested that the humic acid stimulates the stomata opening and then facilitates the entrance of the CuSO₄ to the mesophyll tissue and then start the senescence from inside the leaf rather than burning.

VII International Symposium on Plant Growth Regulators in Fruit Production

Dr. Alfonso Reyes Lopez

https://doi.org/10.17660/ActaHortic.1993.329.58