https://forum.chasedream.com/thread-783752-1-1.html
中国竹子
V5：
Bamboo, China, 公元999年发现，120年开一次花。 于是大家研究它开花时间。
P2学者说开花规律是因为内在生物钟调节，因为不同的种类竹枝，原本开花时间不一样的，一直到同一地域后，开花长短就变得基本一致。这种内在生物钟由外面的光决定。光照时间的长短影响里面的化学物质的光化学反映（光合作用？那个单词是photochemical之类的）时间
P3但是有一个地方的竹子，blahblahblah ，在热带雨林地方seasonal pattern表现不明显,学者解释说因为light difference也不明显。
V6：（V 45）
第一段讲有这么一种竹子120年开次花，应该跟环境无关，因为没有观察到有符合这个时间周期的环境变化，而且它即使被移植到另一个半球也不受影响。
第三段说因为营养不良的竹子和高大威猛的竹子同时开花，那么造成开花的原因一定不是营养，而是竹子内部某种对温度敏感的化学物质随着积累或者减少。（此处复制前人）而在赤道附近的5度纬度内的竹子则很少观察到uniform的开花节奏。。可能因为那里每天与每个季节的温度变化太微弱。
有一题关于bamboo species哪一个文中没提到还是not true之类的
我选了有提到开头那种奇怪的拉丁的竹子名字的那一项。。因为题目问的是整个bamboo species该选项只讲到这种竹子。。大家可以参考。。
V7：（730）
竹子开花好像有一道题是问削弱的，一下哪个会对小P的观点进行削弱
我选的是竹子开花随着温度的变化周期而变化，狗狗里面说是竹子内部某种对温度敏感的化学物质随着积累或者减少，我读的时候是temperature insensitive,应该是温度不敏感才对，所以选择随着温度变化来削弱
好像还有主题题，应该是解释一种现象吧
http://fission.sas.upenn.edu/caterpillar/index.php?action=retrieve&article=Janzen%2C1974bamboo.pdf
原文
(Paragraph 1) In the years 919 and 1114, the mainland Chinese bamboo Phyllostachys bambusoides seeded en masse. Sometime between 1716 and 1735, and againin 1844-l 847, it seeded in Japan, long after being introduced there from China(135). In the late 196Os, transplanted stocks of this bamboo in England,Alabama, and Russia, as well as their parental Japanese stock, flowered again(60, 181, 182, 192). P. bambusoides thushas a seeding cycle ofabout 120 years. Many other species of bamboo have shorter yet stillvery long times between successive synchronized reproductions by seed (Table1). I hypothesize that this behavior is an extraordinary example of satiation of seed predators at the level of the preypopulation, and here explore the literature on the natural history of bamboo todetermine if this hypothesis is reasonable. It is probably untestable in mostcontemporary habitats, owing to the destruction of the relevant organisms ortheir interactions.
WHY IS THE INTERMASTPERIOD SO LONG?
Toexplain the length of the intermast period, I need first to hypothesize how the intermastperiod of a bamboo can lengthen and shorten. It is very unlikely to lengthen bygradual increments. A mutant that waits l-2 years longér than the usual intermastperiod to bear seed may have difficulty outcrossing, and its seeds should fallinto the mouths of many starving animals. If it flowers 5-10 years later than themast crop, it is likely to have an insurmountable pollination problem. Even if itcan self-pollinate, its seeds should be a major attraction for all localanimals. A lengthened cycle appears possible only if the intermast period isdoubled in the mutant genotype. This gives the new genotype the usualprotection of seeding when its relatives are seeding. A genotype with a doubleintermast period would be favored because it should have twice as much reservefor seed production and thus lose a smaller percent of its seeds to the seedpredators at each mast crop. This, however, requires that not all the majorseed predators focus their attention on bamboo clones (clumps) that are bearingparticularly heavily, or that the rhizomes of heavy bearers be well intertwinedwith those of light bearers. As the mutant comes to constitute a progressivelylarger proportion of the genome in the cohort, the plants with the parental(short) intermast period should make up a progressively smaller fraction of thecohort. Collectively, the parental type would be progressively less likely toproduce a mast crop large enough to satiate the seed predators when they seedhalfway between the seed crops of the new genome. Incidentally, this processcould occur, although perhaps less successfully, with a bamboo mutant whoseintermast period is 1.5 times that of the parent-every other mast crop would gainprotection from its relatives.
Anintermast period may be shortened by the following pattern of seed predation. Whena mast crop begins, I expect heavy predation on the early tail of the seeding distribution.In many cases, nomadic animals should arrive shortly and locals should begin tomultiply; thus the primary source of seed consists of those seeds that survive through straightforward predatorsatiation in the middle of the peak of the seeding. However, there may be somecases where the seed production builds up very rapidly, satiating the localanimals before the nomads arrive and local reproduction can occur. This couldresult in the greatest proportion of surviving seeds coming not from the exactcenter of the peak of the seeding distribution but from the earlier (leading)side of the peak. The outcome of such an event would be a gradual shortening ofthe intermast period by a few months each time the seed predators were a bittardy in accumulating. The same process would operate if the usual number of nomadicseed predators did not arrive because, for example, the cohort was too small toattract attention or it was accidentally synchronized with a much larger mastcrop nearby.
Itis important to understand the source of the variation on which the selection describedin the previous paragraph is operating. If those clones that seeded just beforethe peak did so because of environmental plasticity rather than because they weremutants with slightly shorter internal calendars, the outcome of this pattern ofseed predation would be a gradual shifting backward in time of the cycle, butno reduction in the length of the inter-mast period for the cohort. If theearlier seeding plants are mutants, then the intermast period should both shiftbackwards and become shorter.
Ifonly the processes discussed above were responsible for the lengths of the intermastperiods, I would expect the values in Table l to be rather uniformly distributedfrom very small to rather large numbers. However, there is a conspicuous shortage ofintermast periods of less than about 15-20 years. A number of ecologicalprocesses come to mind that should result in the elimination of bamboo cohortswith short intermast periods. Such elimination is a kind of group selection, wherethe cohort can be viewed as the unit of selection.
(Paragraph 2) 2. Whatever the internal calendar counts,it must be contained in all the plant’s parts, since the timing is maintainedby the parts of a plant that has been fragmented. It cannot be measuring storedreserves, since the health and size of the plant within very large bounds doesnot affect the timing of the mast crop. The calendar must be the annual ordaily accumulation or degradation of a temperature-insensitive photosensitivechemical. On the one hand, days or nights would seem easier to count than years, but only1/365 as many physiological events need occur if years are counted. In allparts of the world where bamboogrow, there is enough annual variation in daylength to count the passage of ayear, especially if the timing of the count within that year is unimportant. Itis particularly interesting in this context that accurate mast-seeding bamboos areunknown from closer than about 5 degrees from the equator. The closer to the equator, the moreequal (and minimal) are the two annual cycles of day lengthening andshortening. The African Oxytenanthera abyssinica,which has cohorts with intermast periods ranging from 7 to 21 years, muchsporadic flowering, and relatively unsynchronized cohorts (2, 16,81, 84, 111), hasa distribution bracketing equatorial Africa.
(Paragraph 3) 5. It has never been recorded, but thereshould be geographicvariation in the location of the seeding distribution with respect tothe seasons. While warm weather may allow the more tropical bamboo species toflower and seed at any time of the year [in tropical areas with severe dryseasons every month of the year has some tree species in full flower or fruit(86, 125)], there seems to be a seasonal pattern to bamboo mast seeding. In Japan the “tropical types” tend to flowerin November to February and bear seeds in April and May (254). This would placethe seeds on the ground within a month of the beginning of the monsoon (rainyseason) in most parts of southern Asia. If the seeding distribution is to movebackwards from this time, there must be compensations for any increasedmortality that should occur through the seeds being on the ground during agreater part of the dry season and therefore exposed to seed predators longerbefore germination. If it is to move forwardfrom this time, the seedlings will have a shorter portion of the rainy season inwhich to become established before the next dry season arrives. Ueda also notedthat Phyllostachys (primarily asubtropical genus) flowers in April through June and bears seeds through autumnin Japan. Again, a shift off of this timing could generate increased juvenilemortality through increased seed predation and inclementweather.
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发表于 2017-12-30 14:03:26
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