Effects of key growth conditions on endogenous hormone content in tillering stem bases,germination of lateral buds,and biomass allocation in Indocalamus decorus

Physiological responses and changes in growth of Indocalamus decorus Q.H.Dai under different ecological conditions are essential for further understanding growth regulation and adaptive mechanisms and establishing an evidence-based management system for optimal growth. In this study, the endogenous hormone content in tillering stem bases, germination of lateral buds, and biomass allocation of this bamboo species in different growth environments were investigated. Among the endogenous hormones in the basal stems of tillers, indole-3-pyruvic acid and zeatin riboside were highly correlated with lateral buds that germinated to form shoots, while gibberellic acid was highly correlated with lateral buds that germinated to form rhizomes. The best lateral bud germination characteristics were achieved with full sun, a density of six plantlets per pot, and watering every 6 days. I. decorus plantlets used different resource allocation strategies depending on treatment. Different ecological factors influenced endogenous hormones in the bamboo stem base,which affected lateral bud germination and biomass allocation.

Laws of Trunk Extension and Branching Sprouted from Lateral Buds in Paulownia

Inorder to carry out trunk extension by lateral buds ,the laws of trunk extension and branching sprouted from lateral buds were investigated in 1-year-old seedlings of P.tomentosaxP,fortunei 33 under natural conditions.The results indicated：（1）Under conditions of high density and extensive management,42%of individuals in P.tomentosaxP.fortunei 33 showed pseudo dichotomous branching characteristics and could not extend their trunks in the second year.But other individuals showed the characteristics of sympodial branching and pseudo monopodial branching （not from terminal buds ）and could realize natural trunk extension.All the 3types of branching could be called branching of pseudo asis;（2）The stem form quotieties of extended trunk in all individuals wrer larger in the second year ,but only 14%of them could straight extend their trunks and 86%of them needed2-3years to reach straight trunk estension;（3）Among individuals which could extend their trunks ,from upper lateral buds to lower lateral buds on trunks ,the lengths and diameters of branches sprouted from lateral buds became smaller and smaller ,but the angles of branching up to trunk became larger and larger ,and the fourth pair of lateral branches reached to the largest,Under the fourth pair ,the angles of branches became smaller again and those branches all died.

Temperature Characteristics of Dormancy Development of Terminal and Lateral Buds in Paulownia

In order to probe the death reason of terminal buds and carry out trunk extension by using lateralbuds, the temperature characteristics of dormancy development of terminal and lateral buds in Paulowniatomentosa p. fortunei 33 were investigated by raising cutting branches on different date at 25 ℃ and 15 ℃.The results were as follows: ①The death reason of terminal buds and the first pair of lateral buds was itselfecological adapting strategy, not the injury of early frost and freezing; ②The lateral buds 2, 3 and 4 hadobtained the feature of winter dormancy, and could survive from cold winter, and widen its possible temperaturerange of sprouting to lower temperature by experiencing winter chilling; ③The lateral buds 2, 3 and 4 couldsprout at the same time in spring, but it was difficult to sprout for other lateral buds; ④The sprouting ofupper lateral buds could restrict the sprouting of lower lateral buds at 25 ℃, but not at 15 ℃.

Positive contribution of shoot apex to the growth and flooding tolerance of Hemarthria altissima upon complete submergence

Flooding events tend to destroy the original flood-intolerant vegetation in riparian zones,but the flood-tolerant species can confront the stress,and contribute to the riparian ecosystem.Grass species,Hemarthria altissima,are usually dominant in the riparian zones.This species is considered as good forage which is usually grazed by livestock or mowed by local people.Therefore,the apical tissues of the plants are often removed,and the plants have to grow without stem apexes,during their life cycle.In this study,we aimed to examine the differences in growth performance of intact versus apex-cut individuals of H.altissima upon complete submergence.Two groups of H.altissima plants(with and without shoot apexes)were treated with dark non-submergence and dark complete submergence conditions for 200 days.During the experiment,we measured plant growth,biomass changes in plant organs,and the consumption of non-structural carbohydrates(NSC)by different tissues.During submergence,shoot elongation stopped,and around six lateral buds were developed averagely by each plant without apexes.This growth performance finally caused 60%decline of NSC in underground parts.The relatively intensive consumption of carbohydrates in submerged apex-removed plants induced the 21%stem length decreased under water,which indicated the decreasing submergence tolerance of plants with shoot apex removed.Therefore,we suggest that when using H.altissima for restoring degraded riparian ecosystems,the shoot apexes should be protected from grazing by livestock or harvesting by local people in order to maintain the submergence tolerance of H.altissima.