Cm For Plants Research Articles

Growth of Cucurbita maxima L. plants in the presence of the cycloartenol synthase inhibitor U18666A.

Squash, like other Cucurbitaceae, have unique sterol profiles that offer an excellent opportunity to examine the relationship between sterol biosynthesis and plant growth. To determine the effect of sterol biosynthesis inhibition on squash growth, Cucurbita maxima seedlings with and without cotyledons were subjected to increasing concentrations of the cycloarternol synthase (EC 5.4.99.8) inhibitor 3 beta-(2-diethylaminoethoxy)androstenone (U18666A). Inhibition of shoot growth was concentration-dependent (from 0, 2, 5, 10, and 20 microM); plants with intact cotyledons grew to 26.4, 23.7, 21.6, 20.0, and 15.6 cm, respectively, at the above inhibitor concentrations, compared to 25.5, 19.4, 17.0, 12.0, and 11 cm for plants with severed cotyledons. In plants with severed cotyledons, 10 and 20 microM U18666A caused rapid necrosis of the first two, newly emerged, primary leaves, and halted new leaf formation. Secondary root formation was initially affected at all inhibitor concentrations regardless of whether cotyledons were present or not. Vegetative tissue showed a decrease in the accumulation of the major squash sterol, 7,22-stigmastadienol, accompanied by increased accumulation of minor sterol components. Sterol profiles in cotyledons were unaltered. The data show that sterols are crucial for maintaining plant growth and viability, but do not address the cotyledonary effect on growth with respect to sterol biosynthesis.

Water storage, water use and maize yield for tillage systems on a tropical alfisol in Nigeria

Water storage, water use, and maize yields were studied on a tropical alfisol derived from basement complex rocks in Western Nigeria. The objective was to determine the effects of tillage practices on these factors over a long period since a short term yield record may not be a good basis to evaluate the performance of tillage systems. The study, which lasted for five years (1976–1980) with two growing seasons per year, involved four tillage practices, namely: zero-tillage with mulch; conventional tillage (ploughing and harrowing); plough only and “manual” system which was an imitation of the local peasant practice. The experimental design was randomised complete block with four replications. Results show that in the early seasons the cultivated treatments, namely conventional and ploughing, out-yielded the zero-tillage in the first two years of the study (1976 and 1977). Yields ranged from 2639 kg ha −1 in the zero-tillage to 5240 kg ha −1 in the conventional tillage. However from 1978, the zero-tillage yields were significantly higher ( P < 0.05) than yields from the cultivated treatments with the figures ranging from 4998 kg ha −1 to 5949 kg ha −1 in the cultivated plots and zero-tillage, respectively. The late season yields were also significantly higher in the zero-tillage throughout the study period. The late season is usually a period of low rainfall and the plants go through periods of stress, especially during the critical tasseling and silking period. Water use was similar for plants under the different tillage practices but water use efficiency (WUE), which for the early season ranged between 76.34 kg ha −1 cm −1 in 1980 to 118.65 kg ha −1 cm −1 in 1978, was significantly higher in the zero-tillage most of the time. The leaf stomatal resistances averaged over the measuring periods were 9.2, 9.5, 9.7 and 10.6 s per cm for plants under the zero-tillage, conventional, manual, and plough respectively. These figures were, however, not significant at five percent. There was also no significant difference ( P < 0.05) in the flag leaf water potentials. The average values were −1.39, −1.42, −1.49 and −1.80 MPa for conventional, plough, zero-tillage and manual techniques, respectively.