Poster: Water Relations

Abs # 214: Osmotic Water Permeability of Isolated Protoplasts and Aquaporins during Chilling in Maize

Presenter:	Aroca, Ricardo , raroca@biomail.ucsd.edu
Authors	Aroca, Ricardo  (A)   Chrispeels, Maarten J (A)
Affiliations:	(A): University of California San Diego

Some plant species from tropical regions such as maize are sensitive to low temperatures that often occur during the night or early morning. In such sensitive species, exposure to cold night temperature drying of the shoot, because water loss from the leaves exceeds water uptake by the roots. Little is known about how the low temperature affects water transport at cellular level. Here we report the osmotic water permeability of isolated protoplasts and amount of ZmPIP1 aquaporins as determined by inmunological reactivity from roots, stems and leaves of 11 d old seedlings of two maize genotypes differing in chilling sensitivity (Z7, tolerant and Penjalinan, sensitive) subjected for 3 d to 5ºC. In roots, the osmotic water permeability of isolated protoplasts increased in the tolerant genotype as a result of the cold treatment, while it remained at control values in the sensitive one. In stems, the osmotic water permeability of isolated protoplasts diminished during chilling in the chilling-sensitive genotype, while it did not change in the tolerant one. At the same time, the content of ZmPIP1 proteins decreased in the sensitive genotype plants, while no changes were observed in the tolerant ones. Therefore, there may be a relationship between aquaporins abundance and stem hydraulic conductivity after chilling in maize. In leaves, the osmotic water permeability of isolated protoplasts increased in the sensitive genotype and remained constant in the tolerant one during cold treatment. No changes in ZmPIP1 abundance were found. Therefore the increase observed in the osmotic water permeability could be related to an increase of ZmPIP2 proteins content or the phosphorylation state.