Os efeitos da aplicação foliar de fósforo (Pi) na condutância estomática (gs) e na fotossíntese (A), foram avaliados em genótipos de feijoeiro, A320, Carioca e Ouro Negro, cultivados em potes numa casa de vegetação. Este estudo foi feito durante o dia após a aplicação foliar de 10 g de Pi L-1, em plantas hidratadas, e durante um período de deficiência hídrica iniciada dois ou cinco dias após a aplicação. Durante o dia após a aplicação de Pi, não foi observado nenhuma diferença, entre os tratamentos com e sem Pi, nas trocas gasosas de ambas as cultivares. Durante a desidratação, a aplicação de Pi não causou aumento de gs, mas causou aumento de A, nas medições às 0900, 1200 e 1500 horas, nas cultivares (Carioca e Ouro Negro), mas com um efeito maior na cultivar Ouro Negro, principalmente às 1200 horas. A eficiência intrínseca do uso da água (EIUA) também foi superior nas plantas com suprimento foliar de Pi. Quanto aos componentes da produção, a aplicação de Pi causou aumento do número de vagens das plantas da cultivar Ouro Negro, sob desidratação. Portanto, a aplicação de Pi foliar pode reduzir o efeito de uma desidratação quando aplicado dois dias antes da suspensão da irrigação. Além disso, o potencial fotossintético (Ac) de Ouro Negro com Pi foi superior ao de A320, com e sem Pi, na seca máxima, e ao A320 sem Pi, na reidratação. A dissipação térmica, não fotoquímica (NPQ), do genótipo A320 sem Pi foi maior que com Pi e que a do Ouro Negro, com e sem Pi, na reidratação, provavelmente devido aos menores valores de A neste tratamento sem Pi. O uso de fosfato de amônio substituindo a uréia ou o sulfato de amônio, que são aplicados aos 25 DAE, é recomendável. / The effects of foliar Pi supplying (Pi) on stomatal conductance (gs) and photosynthesis (A) were measured in genotypes, A320, Carioca and Ouro Negro, grown under greenhouse condition. Measurements of gs and A were taken one day after Pi application (10 g L-1) on well-irrigated plants, and during drought stress period beginning two or five days after Pi supplying. During the day after Pi application, it was not observed any difference on gas exchange of genotypes (Carioca and Ouro Negro) due to the treatments with and without Pi. During water stress, the Pi supplying did not cause increase of gs, however, caused increase of A at 0900, 1200 and 1500 h in both genotypes. This effect was higher when considered Ouro Negro at 1200 h. The intrinsic water use efficiency (IWUE) was also increased in Pi-supplied plants. The Pi supplying caused increase on pod number of Ouro Negro plants under water deficit. These results suggest that the foliar Pi application may reduce the effect of water deficit on photosynthesis when supplied two days before the water withholding. In addition, the O2 evolution (Ac) on Ouro negro with extra Pi was higher than for A320, with or without Pi, at the last day of the mild water deficit, and it was higher than A 320 with extra Pi at rehydration. The non-photosynthetic quenching (NPQ), was higher for A320 without Pi at recovery, probably due to the smaller values of A at this treatment. The use of ammonium phosphate, instead of urea or ammonium sulphate to be applied as usual 25 DAS, is recommended.

From the Proceedings of the 1977 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 15-16, 1977, Las Vegas, Nevada / The root system of shrub live oak (Quercus turbinella) was studied in an initial effort to classify the major Arizona chaparral shrubs as potential users of soil water based on root system characteristics. The root system was of the generalized type with a taproot, many deeply penetrating roots, and a strong lateral root system. Roots penetrated 21 feet to bedrock through cracks and fractures in the rocky regolith. A dense network of small surface laterals radiated from the root crown and permeated the upper foot of soil. Because of its root system, shrub live oak is well adapted to utilize both ephemeral surface soil moisture as well as deeply stored moisture. Emphasis is placed on the importance of a knowledge of the root systems of chaparral shrubs and depth of the regolith in planning vegetation conversions to increase water yield.

From the Proceedings of the 1978 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 14-15, 1978, Flagstaff, Arizona / Algal growth and oxygen evolution at the soil -water interface of soil recharge basins intermittently flooded with secondary sewage effluent (SSE) produced diurnal fluxes in dissolved oxygen (DO) in the SSE and redox potentials (Eh) in the SSE and the surface soil of the basin. The maximum daily DO-% saturation in the SSE during flooding ranged from 30 to 450 %, depending on the length of flooding and seasonal effects of temperature and solar radiation. Diurnal cycles of Eh in the SSE and the top 0 to 2 cm of soil indicated that oxygen production by algae and bacterial nitrifying and denitrifying reactions at the soil-water interface are occurring daily for limited periods during flooding and that these reactions might contribute to the net-N removal and renovation of SSE by soil filtration.