Uso de cubiertas fotoselectivas para la producción de plántulas de hortalizas

"Se evaluaron ocho cubiertas plásticas fotoselectivas aplicadas en microtúneles, con el objetivo de comparar variables agronómicas y anatómicas en tres genotipos de lechuga y dos genotipos de tomate de cáscara. La investigación se realizó en la Universidad Autónoma Agraria Antonio Narro, en marzo del 2004. Se utilizó un diseño experimental de bloques al azar con arreglo en parcelas divididas, donde el factor A (parcela grande) fueron ocho colores de cubierta y el factor B (parcela chica) cinco genotipos. En las plántulas de lechuga se estimaron las variables, peso fresco aéreo (PFA), peso seco aéreo (PSA), peso fresco de raíz (PFR), peso seco de raíz (PSR), altura de planta (AP) y numero de hojas (NH); presentando diferencias altamente significativas para todas las variables. En el caso de tomate de cáscara las variables estimadas fueron altura de planta, numero de hojas, peso fresco de tallo, peso fresco de raíz, peso seco de tallo, peso seco de raíz, materia seca total, numero de estomas abaxiales, numero de estomas adaxiales, numero de vasos del xilema y área total de vasos del xilema, encontrando diferencias altamente significativas en todas las variables, excepto en peso fresco de tallo y numero de estomas abaxiales, que resultaron significativas. En ambos casos los resultados nos indican que al menos una cubierta fotoselectiva es estadísticamente diferente del resto. De los resultados obtenidos es posible concluir que las cubiertas de color amarillo y blanco influyen favorablemente en el aumento de biomasa logrando plántulas de mayor calidad en lechuga y tomate de cáscara; añadiendo en este ultimo caso la cubierta transparente con resultados similares."

"Eight plastic photoselective coves were evaluated and applied on microtunnels, to compare agronomic and anatomic variables on three lettuce genotypes and on two in husk tomatoe. Investigation was made at the Universidad Autonoma Agraria Antonio Narro on March 2004. A random experimental block design was used, arranging it in divided plots, where factor A (big plot) were eight colors of cover and, factor B (small plot) were five genotypes. In lettuce seedlings aerial fresh weight (AFW), aerial dry weight (ADW), aerial dry weight (ADW), fresh root weight (FRW), dry root weight (DRW), plant height (PH) and leaf number (LN), variables were estimated, presenting highly significant differences for all variables. In tomatoe, estimated variables are plant height, leaf number, fresh stem weight, fresh root weight, dry stem weight, dry root weight, total dry matter, abaxial stomatal number, adaxial stomatal number, xylem vase number and total xylem vases area, having highly significant differences in all variables, except on fresh stem weight and abaxial stomatal number, which were significant. In both cases, results indicate that at least one photoselective cover is statistically different from the rest. From results obtained, is possible to conclude that yellow and white covers influence favorable on the biomass increase, having higher quality lettuce seedlings and husk tomatoe, adding in this last case, a transparent cover with similar results. The growth retardant was sprayed on trees early in the spring when shoot growth reached 5 cm in length. The concentration dosages of P-Ca were 0 (control), 125, 175 and 250 mg/L. The results have shown that P-Ca at any concentration reduces shoot and internodal final length. The leaf number per shoot was also reduced in all P-Ca treated trees. The growth retardant at 175 and 250 mg/L increased total yield per tree reflected with a higher fruit set and fruit weight. Harvested fruits from these treatments showed an increase in soluble solids and firmness. The endogenous hormone status was analyzed on apple trees treated with Prohexadione-Ca at 250 mg/L. The levels of gibberellins and auxins in shoot tips was decreased soon after the P-Ca application; whereas the cytokinin content increased. In these P-Ca tissues, it was possible to identify gibberellins A9, A20, A51 and A53; zeatin and IAA. In control samples, zeatin, IAA and gibberellins A1, A4, A7, A9, A51 and A53 were identified. Prohexadione-Ca did not modify the endogenous hormone profile in immature seeds."