Name: 樹木如何知道什麼時候是春天？ (How Do Trees Know When It's Spring?)
Uploaded: 2021-01-14T07:46:11.000Z
Duration: 3 min 45 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

We went to the National Arboretum here in D.C.

but it's sort of the same thing for a tree.

and what it looks like when it's in flower, and everything,

I'm the head of horticulture and education

We have a scientific mission primarily here,

How do trees know to bloom in the spring?

Actually, it has more to do with the length

of the nighttime than it does with temperature.

it gets warmer, and the buds start coming on the trees,

Plants have a funky little molecule in them

The hourglass, or the molecules, is flipped

the plant gets the idea that we should hold off.

But then you have that one magical night that

The bud gets a signal that it's time to get going,

and then we have a period of warmer temperatures

those buds will get the signal to hang way back

What're signs that people can look for to say:

Of course, the obvious thing is bud swell.

From a distance, you can see if something looks

if you look closely, you'll see the little stamens

Most plants have two different kinds of buds,

and you can see that very clearly this time of year.

You have big, fat ones that are flower buds.

And then, very often you have closer to the tip,

skinny, kind of slender ones that are vegetative buds

The purpose of a tree blooming is one thing,

if we injured the lot of the root system on it,

and people will misinterpret that as health.

Actually, that's a: I know I'm going to die!

But before I die, I want to have lots of kids,

I mean, even if you look at them structurally,

and efficiently built than any of our buildings.

If you're a tree, you can't move some place better

I guess I'm always really surprised at how