Aislados de Bacillus provenientes de la rizósfera de cactus incrementan la germinación y la floración en Mammillaria spp. (Cactaceae) / Bacillus isolates from rhizosphere of cacti improve germination and bloom in Mammillaria spp. (Cactaceae)

Las cactáceas son la vegetación característica de las zonas áridas en México, donde las lluvias son escasas, la evapotranspiración es elevada y la fertilidad de los suelos es baja. Las plantas han desarrollado estrategias fisiológicas como la asociación con microorganismos en la zona de la rizósfera para incrementar la captación de nutrientes. En el presente trabajo se obtuvieron 4 aislados bacterianos de la rizósfera de Mammillaria magnimamma y Coryphantha radians, los que fueron nombrados como QAP3, QAP19, QAP22 y QAP24 e identificados genéticamente como pertenecientes al género Bacillus. Estos aislados exhibieron in vitro propiedades bioquímicas como solubilización de fosfatos, producción de ácido indolacético y actividad ACC deaminasa, que se relacionan con la promoción del crecimiento de las plantas. Dicha promoción fue ensayada inoculando semillas de M. magnimamma y evaluando luego algunos parámetros. Se encontró que todos los aislados incrementaron la germinación desde un 17% hasta un 34,3% (con respecto a las semillas testigo sin inocular); el aislado QAP24 fue el que presentó el mayor efecto en este sentido y permitió la germinación de todas las semillas viables (84,7%) 3 días antes que en el testigo. La inoculación de este aislado en plantas de Mammillaria zeilmanniana mostró un efecto positivo sobre la floración: en 2 meses dentro del período de un año se detectó un incremento en el número de plantas en floración con respecto a las plantas testigo, de hasta el 31,0% en uno de ellos. Se concluye que los aislados de Bacillus spp. caracterizados poseen potencial para ser empleados en programas de conservación de especies vegetales de zonas áridas.

Cacti are the most representative vegetation of arid zones in Mexico where rainfall is scarce, evapotranspiration is high and soil fertility is low. Plants have developed physiological strategies such as the association with microorganisms in the rhizosphere zone to increase nutrient uptake. In the present work, four bacterial isolates from the rhizosphere of Mammillaria magnimamma and Coryphantha radians were obtained and named as QAP3, QAP19, QAP22 and QAP24, and were genetically identified as belonging to the genus Bacillus, exhibiting in vitro biochemical properties such as phosphate solubilization, indoleacetic acid production and ACC deaminase activity related to plant growth promotion, which was tested by inoculating M. magnimamma seeds. It was found that all isolates increased germination from 17 to 34.3% with respect to the uninoculated control seeds, being QAP24 the one having the greatest effect, accomplishing the germination of viable seeds (84.7%) three days before the control seeds. Subsequently, the inoculation of Mammillari zeilmanniana plants with this isolate showed a positive effect on bloom, registering during two months from a one year period, an increase of up to 31.0% in the number of flowering plants compared to control plants. The characterized Bacillus spp. isolates have potential to be used in conservation programs of plant species from arid zones.

In vitro flowering – A system for tracking floral organ development in Dendrocalamus hamiltonii Nees et Arn. ex Munro.

Dendrocalamus hamiltonii plants are slender and tall (15-25 m) thereby, rendering tagging, sampling and tracking the development of flowers difficult. Therefore, a reproducible system of in vitro flowering was established for tracking the stages of flower development. MS medium supplemented with 2.22 µM 6-benzylaminopurine, 1.23 µM indole-3-butyric acid and 2% sucrose was optimized as the flower induction medium (FIM) wherein 28 and 42 days were required for the development of gynoecium and androecium, respectively. Six distinct stages of in vitro flower development were identified, and the flowers were comparable with that of in planta sporadic flowers. Pollen viability of the in vitro flowers was higher than those of in planta ones. The in vitro system developed in the present study facilitates easy tracking of different stages of flower development under controlled environmental conditions. It can also be used for medium- or long-term storage of pollens and manipulation of in vitro fertilization.

Foliar application of Zn at flowering stage improves plant’s performance, yield and yield attributes of black gram.

Black gram plants subjected to varying levels of Zn supply (0.01 to 10 µM Zn) showed optimum growth and dry matter yield in plants receiving 1 µM Zn. The dry matter yield of plants decreased in plants receiving 0.01 and 0.1 µM Zn (deficient) and excess levels of Zn (2 and 10 µM Zn). The plants grown with Zn deficient supply showed delayed flowering, premature bud abscission, reduced size of anthers, pollen producing capacity, pollen viability and stigma receptivity resulting in poor pod formation and seed yield. Providing Zn as a foliar spray at pre-flowering stage minimized the severity of Zn deficiency on reproductive structure development and enhanced the seed nutritional status by enhancing seed Zn density, seed carbohydrate (sugar and starch content) and storage proteins (albumins, globulins, glutenins, and prolamines).

Effect of salicylic acid on morphological and biochemical attributes in cowpea.

Effects of salicylic acid (SA) on seed germination, seedling growth, flowering and biochemical activities were studied out in four cowpea (Vigna unguiculata) genotypes in control environments. The results revealed that both germination and seedling growth were negatively affected by 0.02%. SA application, however did not affect the size of full expanded buds, time of 50% flowering and date of flower initiation. A maximum increase in peroxidase (EC1.11.1.7) activity was observed in UPC 4200 over other genotypes. No significant change in the content of total soluble and intercellular fluid proteins was observed except in UPC 4200 genotype. SA induced accumulation of total soluble sugars more at flowering stage than at seed setting stage. It is evident from the present study that UPC 4200 genotype was more responsive to salicylic acid both in terms of increased peroxidase activity and less negative effect on morphological attributes, thus suggesting its wider use without negative impact on environment as salicylic acid has been reported in plants.