Comportamento de duas cultivares de algodoeiro herbáceo (Gossypium hirsutum, L.r. Latifolium Hutch L.) em baixos níveis de água disponível do solo.

Abstract

The principal objective of this work was to study the behavior of two cotton cultivars, XCNPA Precoce-1' and XCNPA IH', grown under water stress conditions from the seed germination until the opening of the fruits . The experiment was carried out under greenhouse conditions, using PVC pots with 41cm heights and diameters of 15cm, containing 10 kg of a dry sandy soil, in a random block experimental design, with 3 replications in a factorial scheme (2x 4), where the factors considered were 2 cultivars and 4 water stress leveis . The evaluations were done at four stages of plant growth, corresponding to 36, 52, 72 and 98 days a f t e r the sowing.At the sowing time, the soil moisture content in all pots was kept at field capacity untill the start of treatments, that happened when the humidity level lowered t o 63%, 43%, 23% and 3% of the available soil water. After this time, the available soil, water leveis were maintained by weighing the pots, with suplementai iirrigation when i t was necessary, until the levels listed above. The results obtained showed that both cultivars need little water at the initial stage of growth. The CNPA-7H cultivaris more efficientin converting water into vegetative parts , while XCNPA Precoce-1' has more water use efficiency in relation to flowering and fruitage . CNPA Precoce-1 c u l t i v a r tends t o be more resistant to water deficit. There are correlations , expressed by regression equations, between the leaf of the first fruit branch (in terms of its mean length, its dry matter weight and it s leaf area) and the plant leaf area, for both cultivars . The mean leaf area for each cultivar is significativelly correlated with the available water level of soil . The plants developed higher root /aerial part ratio in lower availaber water leveis , with cv. CNPA-7H overcoming cv. CNPA Precoce-1.