There is increasing interest in understanding the costs and benefits of increased size and prolonged lifespan for plants. Some species of trees can grow more than 100 m in height and can live for several millennia, however whether these achievements are obtained at the cost of some other physiological functions is currently unclear. As increases in size are usually associated with ageing, it is also unclear whether observed reductions in growth rates and increased mortality rates are a function of size or of age per se. One theory proposes that reduced growth after the start of the reproductive phase is caused by cellular senescence. A second set of theories has focussed instead on plant size and the increased respiratory burdens or excessive height. We report on experimental manipulations to separate the effects of extrinsic factors such as size from those of intrinsic factors such as age for four tree species of contrasting phylogeny and life history. For each species, we measured growth, gas exchange and leaf biochemical properties for trees of different ages and sizes in the field and on propagated material obtained from the same genetic individuals but now all of small similar size in our common gardens. For all species, evidence indicated that size, not cellular senescence, accounted for the observed age-related declines in relative growth rates and net assimilation rates. Two species exhibited evidence of genetic control on leaf characters such as specific leaf area, although size also exerted an independent, and stronger, effect. We found partial support for the theory of hydraulic limitations to tree growth. The lack of a marked separation of soma and germline, an unlimited proliferation potential of meristem cells and the exponential increase in reproductive effort with size all help explain the lack of a senescence-induced decline in trees. It is possible that trees much older than the ones we sampled exhibit senescence symptoms.

Vegetative propagation techniques such as grafting can be used, in conjunction with field studies, to decouple the relative effects of age and size on tree metabolism and growth. Despite interest in this approach, little attention has been paid to the best metrics for assessing the growth performance of grafted plants over time. Based on an analysis of the grafting literature and our own data, we show that the choice of metrics to assess tree growth can entirely change the conclusions reached about the relative importance of age versus size. We recommend that absolute as well as relative rates of growth are calculated and that scion size be standardized as much as possible at the start of the experiment. Once proper metrics are chosen, all of the available published evidence is largely concordant with two concepts: (1) age-mediated controls of tree growth are likely to be important during the first few years of a tree's life (before phase change); and (2) after the first few years of a tree's life, size-mediated factors largely prevail over age-mediated factors in determining tree growth rates. We found no support for theories invoking age-mediated sink limitations in old trees.

Abstract. Ikhsan Z, Hidrayani, Yaherwandi, Hamid H. 2020. The diversity and abundance of Hymenoptera insects on tidal swamp rice field in Indragiri Hilir District, Indonesia. Biodiversitas 21: 1020-1026. Hymenoptera is one of the four largest insect orders and it plays a vital role in human life as pollinators, parasitoids, and predators. Hymenoptera parasitoids are particularly important as agents of biological control of pest. The objective of this research was to study the diversity and abundance of Hymenoptera on tidal swamp rice field in Indragiri Hilir District, Riau Province, Indonesia. Samplings were conducted in 3 sub-districts of rice production centers, namely Batang Tuaka, Keritang and Reteh, using four trapping techniques (i.e. insect net, malaise trap, pitfall trap, and yellow pan trap). Shannon diversity index (H '), Krebs evenness index (E), and Jaccard similarity index (Is) were calculated. We found 4,701 individuals consisting of 39 families and 319 species of Hymenoptera at the three studied areas. Tidal swamp rice in Indragiri Hilir District had a high species diversity of Hymenoptera parasitoids and Hymenoptera predators, but a moderate species diversity of Hymenoptera pollinators. Species diversity and evenness of Hymenoptera parasitoids and predators were higher in Keritang than in Batang Tuaka and Reteh. The families of Formicidae, Braconidae, Ichneumonidae, and Scelionidae had the highest number of species, while Formicidae, Scelionidae, Diapriidae, and Braconidae had the highest number of individuals. Based on these findings, the abundance and diversity of Hymenoptera insects in Indragiri Hilir District have the potentials to be developed as biological agents to control pests on tidal swamp rice in this area.

The use of plant varieties can affect the presence and extent of pest attacks. Resistant varieties will cause a lower attack rate compared to susceptible varieties. It is not yet known which varieties of maize are resistant to Fall armyworm (S. frugiperda) (FAW) in the field, because this pest is an invasive pest and entered Indonesia one year ago. Research has been carried out to study the distribution, population, and level of S. frugiperda attack on maize varieties planted by farmers in the field. The research was conducted at the first location this pest was reported in West Pasaman district, West Sumatra, Indonesia. Survey on farmers’ corn with a sampling method: purposive random sampling. Samples were taken from different varieties of corn and showed signs of S. frugiperda attack. Observations were made on the varieties planted by farmers, symptoms, larvae population, and S. frugiperda attack rate. The results of the observations were that several trademarks of maize varieties grown by farmers were: Pioneer 32, Pertiwi, Bisi 18, NK7328, and NK212. The symptoms of this pest attack were the same for all varieties of maize, while the attack rate was significantly different at the 5% level. The attack rate ranged from 6.0 to 96.0%. The lowest attack percentage was on variety Bisi18, and the highest was on variety NK212. The population of S. frugiperda larvae was found in all varieties of maize with an average of 0.70 larvae per stem.

Abstract. Yanti Y, Hamid H, Reflin, Warnita, Habazar T. 2019. The ability of indigenous Bacillus spp. consortia to control the anthracnose disease (Colletrotricum capsici) and increase the growth of chili. Biodiversitas 21: 179-186. Anthracnose disease caused by Colletotrichum capsici can reduce yields of chili up to 80%. The control of anthracnose disease is generally carried out using synthetic fungicides. However, the use of these fungicides can pollute the environment and harm human health. One alternative control that needs to be developed is the use of Bacillus spp. as a biocontrol agent. The study was conducted to obtain an indigenous Bacillus spp. consortium that compatible as a biological agent for the control of the anthracnose diseases and promoting the growth of chili plants. The experiment was arranged as a completely randomized design, consisted of three stages, namely: 1) inhibitory test of indigenous Bacillus spp. against C. capsici in vitro, 2) compatibility test of indigenous Bacillus spp. and 3) Test of indigenous Bacillus spp.consortium for controlling C. capsici and promoting the growth of chili. The results showed that eight species of indigenous endophytic bacteria could inhibit the growth of C. capsici in vitro. All combinations of indigenous Bacillus spp. were compatible for controlling C. capsici. Four combinations of Bacillus spp. were able to increase the growth of chili plants. K1 consortium (Bacillus pseudomycoides strain SLBE 3.1 AP, Bacillus thuringiensis strain SLBE 2.3 BB, Bacillus toyonensis strain AGBE 2.1 TL) was the best consortium for controlling C. capsici.